Systematic Review of Tyre Technology

1
Yasuhiro Ishikawa■ Abstract
The history of the tyre starts with the use of the wheel, using a log or its x-section. Tyres then cameinto common use on the wheels of carts or horse carts. The pneumatic tyre was originally invented
by R.W. Thomson in the middle of 19th century. Then at the end of 19th century, a pneumatic tyre
for automobiles was invented. The history of the Japanese rubber industry also starts around thistime: the latter half of 19th century, out of which the tyre industry then developed. The history of theJapanese tyre industry is divided into the three following stages:
Stage 1: Dawn of the Industry
The Japanese tyre industry began in the Meiji era (1868-1912) with the initial development of theJapanese rubber industry. The foundation of Tsuchiya Rubber Factory in 1886 (Meiji 19) is generally
taken to herald the start of the Japanese rubber industry, approximately fifty years after the inventionof vulcanization by C. Goodyear in 1839.
Stage 2: Age of GrowthThis period from the beginning of the Taisho era (1912-1926) to the end of World War II saw the
introduction to Japan of rubber technology from foreign countries, when domestic industry as awhole was developing with the importation of various technologies. The founding of domestic tyre
manufacture dates from this period. Domestically-developed tyre technology showed dramatic
growth during the War and played an important role in military supplies.
Stage 3: Maturity
This stage covers the time from the end of the War II to the present. Although tyre manufacturing
suffered significant damaged during the War, recovery was rapid, and tyre technology saw further
dramatic development with the growth of motorisation. This period of growing post-War
motorisation is divided into three parts.
The first period was when new materials such as nylon and synthetic rubber were developed. In thisperiod, processing technology that could deal with these new raw materials was developed for thetyre.
The second period saw tyre construction completely change from bias to radial tyres. Thissignificant development in tyre construction saw not only major changes in materials, such as the useof steel cord, but also in the modification of production equipment.
In the third period, the various elemental technologies were integrated, resulting in the further
refinement of the steel radial tyre and the achievement of its durability in terms of adhesion between
1
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the rubber and steel cords, and preventing rubber fatigue throughout the tyre’s working life.
Following this period, better motion performance was required of tyres. However, it was well known
that a tyre with lower rolling resistance had the problem of lower skid resistance. This performancetrade-off is still major issue with tyres today. In addition, the improvement of ride quality, such as
the reduction of noise and vibration, came to be increasingly important in tyre performance.
Therefore, more exacting demands have been made of tyre performance since the 1980s.
Many epoch-making technologies have been developed since the War in the areas of raw materials
and construction, and which have then been incorporated into tyre technology. How much Japan has
contributed to these developments in tyre technology is debatable; however, Japanese tyre
technology has recently been earning itself recognition in the tyre industry by further consolidatingthese technologies. The next decade will see rising demand for environmentally friendly solutions,spurring the need for new technology that addresses this major issue.

■Profile■Contents

Yasuhiro Ishikawa
Chief Survey Officer, Center of the History of JapaneseIndustrial Technology, National Museum of Nature andScience

1. Introduction

March 1969

3. Dawn of the Japanese Rubber Industry (The Age ofApril 1969
October 1993

July 1996
July 2001
July 2003
July 2005
January 2008
2001-2002
Present

Completed Master’s degree at Tokyo
Institute of Technology Graduate
School of Engineering
Employed in the laboratory at
Yokohama Rubber Company
Head of the Tire Materials
Development Department, Yokohama
Rubber Company
Director of the Tire Materials
Development Laboratory, Yokohama
Rubber Company
Director, Yokohama Rubber Company
Chief Engineer, Yokohama Rubber
Company
Consultant, Yokohama Rubber
Company
RetiredVice President, The Society of Rubber
Science and Technology, Japan
Chairperson, Moulded Processing
Technology Subcommittee, ResearchCommittee, The Society of Rubber
Science and Technology, Japan
Doctor of Engineering

2. Creation of the Tyre

Early Compounding Techniques)
4. Stage of Growth: Creation of the Domestic Tyre
Industry
5. Stage of Maturity: The Age of Motorisation
6. The Coming of Age of Radial Tyres
7. Detailed Description of Tyres Requiring Additional
Performance
8. Summary of Technology Progress
List of Candidates for Registration

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1. Introduction
1.1. Outline of Tyre Technology

1.2. Progress of Japanese Tyre

Tyres are an essential component to theTechnology (Systematisation) (See Fig. 1.1)

establishment of the automobile mechanism.

The history of the tyre industry in Japan

Tyres can be viewed as having the following

can be divided into three stages.

four functions 1)).

Stage 1: Dawn of the Industry – Meiji Period.

- Bearing a load (support)

The dawn of the Japanese rubber industry saw- Acting as a spring (absorption)some rudimentary developments.

- Conveying driving and braking forces

Stage 2: Stage of Growth – Early Taisho Period(transmission)to the Second World War. From the Taisho- Facilitating steering of the vehicle (turning)

Period to the early Showa Period, Japan either

These are vital functions in which the tyres as

introduced overseas technology or started

part of the vehicle serve as an intermediary indeveloping its own independent technology.

establishing a mutual relationship between theThis technology later played a role as military

vehicle and the surface of the road.

goods during wartime.

The history of tyre technology is the history ofStage 3: Stage of Maturity – Post-War to thedevelopments carried out to achieve thesepresent. While various companies sufferedfunctions. This technology is expansive induring the war, they bounced back from theextent, combining many materials to form theravages of war and, accompanied by the latermechanics of the tyre, which in turn plays aspread of motorisation, grew rapidly to thecomplexpresent day 2).

role

being

incorporatedasacomponent into the automobile mechanism.

The Stage 3 post-war age of motorisation canThus, tyre technology is expansive and has

be divided into three further stages.

come to hold an important place in the industry.

The first stage was the age of incorporating

Tyres are a rubber product. Rubber technology

new materials into the existing bias tyres.

had a long history before the invention of theInstead of cotton or rayon for reinforcing,tyre in the 19th

century. The technology

followed the same path in Japan, albeit later.

synthetic nylon appeared; synthetic rubbers
such as SBR (styrene-butadiene rubber) and BR(butadiene

rubber)also

appeared

asareplacement for natural rubber. This stage isremembered as an age in which new materials
appeared and much effort was spent on
processing techniques in order to fully utilisethem (post-war – 1960s)
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Part 1 (Tyre Outline)
Chapter 1: Introduction, Chapter 2: Creation of the Tyre
Part 2 (Progress of Japanese Tyre Technology)(2)
Chapter 4: Creation of theJapanese Tyre Industry
Taisho Period, Early Showa
Period, End of the War(1)
Chapter 3: The Start of theJapanese Rubber Industry– End of the Meiji Period (Dawn)(3)
Chapter 5: Post-War Developments
Post-War –(Stage of Maturity; Age ofMotorisation) (Stage of Growth;Technology Imports; Domestic
Production Period)
Chapter 5
The Age of Motorisation

Introductory Stage

Stage 3
Stage 2
Stage 1The Age of
The Age of Radial
The Age of New
Structural Change
Tyres
Materials
Stage of Growth(Bias → Radial) (The Age of Evolution)(Use of Nylon,
Systematisation Trends
Chapter 6
Synthetic Rubber) (Use of Steel Cord,
Polyester)
Chapter 6
The Coming of Age of Radial Tyres;
The Age of Evolution
Stage of Maturity
Stage 1
Stage 2
Stage 3
Durability
Manoeuvrability Sensation and(Change of(Change of
Sensitivity
Materials) Materials/Structure) (Change ofChapter 7 Additional Performance
Structure)
Stage 4: Integration

Aircraft; Construction Vehicles; Two-Wheeled Vehicles; StudlessFig. 1.1. Progress of Japanese Tyre Technology (Systematisation)
The second stage was the age in which tyre

durability, fraught with issues such as how to

structure changed from bias to radial. Thisfasten steel cord and rubber together andmajor

dealing with separation due to breakdown inchangeaccompanied

in

tyre

structure

was

by

major

changesinthe rubber. 1970s-1980s.

manufacturing facilities. The appearance of

The second was the age of ensuring highsteel cord reinforcing meant major changes inmanoeuvrability as a required performancetyre structure and manufacturing facilities,

over and above durability. This was affectedaccompanied by major progress in tyreby the 1979 oil crisis, with a rapidly-increasing

performance.

demand for improved fuel economy. This

The third stage is the age of integrating various

presented some issues with safety, since tyres

elements of existing technology and improving

with good fuel economy moved easily but

radial tyre performance. This stage can bewere difficult to stop. Competition soared

divided into a further four stages.

around the world to resolve this paradox.

The first was the age of perfecting radial tyre

1980s onwards.

durability. This was an age of ensuring

The third was the age of increased sensation
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and sensitivity, such as noise and vibration.

normal. These have played a role in

1980s onwards.

presenting tyre technology with the challenges

The fourth was the coming of age of tyreof additional performance (such as heat

performance. There was a demand for a highresistance and friction on ice).

degree of all-round perfection, with high levels

Broadly, the progress of post-war technologyof durability and manoeuvrability as well as

development has alternated between material

sensation and sensitivity factors such as noise(nylon and synthetic rubber), structural (radial

and vibration taken care of. In other words, ittyres), material (rolling resistance due to radial

was an age of demand for perfection in allmaterial durability and variety of SBR) andcomponent technologies in all areas ofstructural

performance and of theories developed to thatvibration, ride comfort). At each stage, theend.

most suitable techniques have been eagerly

Other tyres (such as aircraft tyres, tyres forsought out and surpassed.

(sensation,

sensitivity,

noise,

construction vehicles, tyres for two-wheeled

requireadditional performance capabilities thanvehiclesandstudlesstyres)Side Reinforcing
RubberHigh-Performance
Fuel-Efficient Tyre
Passenger Vehicle Tyre

Racing Tyre

Construction
Vehicle Tyre

Studless Tyre

Run-Flat Tyre

Truck/Bus Tyre

Aircraft Tyre3)

Fig 1.2. Current Types of Tyres Gomu / Erasutomā to Mirai no Kōtsū [Rubbers / Elastomers andFuture Transportation] Rubber Technology Forum, ed., Gomutimes, March 2010, p

5National Museum of Nature and Science
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breakthroughs in which Japan actively

Tread Belt Undertread

contributed to epoch-making technology, suchas the change from bias tyres to radial tyres, orthe appearance of synthetic rubber or steel
cords. However, Japan’s later presence in the

Sidewalltyre industry has been unwavering; ultimately,

Inner Liner
Carcass Ply
RubberChaferits strength in the industry – its operational
strength combined with its technological

Bead Filler

strength (optimisation strength) – is significant.

Bead Chafer

This is probably due to the significant presenceof its technological strength based on

Fig. 1.3. Tyre Structure (Radial Tyre)

manufacturing. It is also probably a(Cross-Section)

combination of the Japanese-style technology
prioritisation (diligent manufacturing for

Looking back through this history of

optimisation rather than major innovation) anddevelopment, there are very few major

the emphasis on companies (enterprises).

Tyre Size Designations
Tread Width
Size of Rim Diameter (14 inches)
Tyre Structure Code (Radial)
Aspect Ratio (60%); Height/Width
Cross-Section Width (195mm)
Bias Tyre
Ply Rating(4-ply; equivalent strength of four
layers of reinforcing)Rim Diameter (13 inches)
Cross-Section Width (6.15 inches)

Outer Diameter of Tyre

Radial Tyre

Rim Width

Cross-Section Width

Cross-Section
HeightRim
DiameterFig. 1.4. Tyre Dimensions. Aspect Ratio = Cross-Section Width / Cross-Section Height6
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However, stricter environmental measures willNotes on Writing:mean further hurdles will need to be crossed in

1. There are many types of tyres; it was not

future. Mere optimisation will not be enough;possible to describe them all. This reportmajor breakthrough will be necessary.

does not touch on racing tyres, agricultural
tyres or bicycle tyres.

Breaker

Belt

Carcass

Carcass

2. Regarding company names.

Company

names have been dealt with as follows forthe writing of this report. The former nameof the company has been used where doing
so has served to better convey the content.

a) Bias Tyreb) Radial Tyrea) Bias Tyre : Carcass is oriented in a biased
directionb) Radial Tyre : Carcass is oriented in a radial
direction
Fig. 1.5. Comparison of Tyre Structures (Bias /Radial)(Name used):(Former name(s); current official name)

Sumitomo Rubber:

Dunlop Rubber Company (Far East); Dunlop Rubber Company(Japan); Chuo Rubber Industries(Chuō Gomu Kōgyo
Kabushikigaisya); Sumitomo Rubber Industries

Yokohama Rubber:

Yokohama Rubber Manufacturing Company(Yokohama Gomu Seizou
Kabushikigaisya); Yokohama Rubber Company

Bridgestone:

Bridgestone Tire Company; Nippon Tire Company(Nippon Taiya
Kabushikigaisya); Bridgestone Tire Company; Bridgestone
Corporation

Toyo Rubber:

Toyo Tire Industrial Company(Tōyō Taiya Kabushikigaisya); Toyo
Rubber Manufacturing Company(Tōyō Gomu Kakou
Kabushikigaisya ) ; Toyo Rubber Industrial Company(in order of founding)
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3. Handling of Numbers in the Japanese
Text, years, months and days citedfrom sources originally writtenvertically, such as company histories
and The History of the Japanese

Rubber Industry, are written in
Sino-Japanese characters in theJapanese texts. Since the Japanese
text of this report is writtenhorizontally, it uses Arabic numerals.

Cited references:
1) Hattori, Rokuro: Taiya no Hanashi [The Story of the Tyre], Taiseisha, June 1992, p. 34.
Jidōsha-yō Taiya no g [Studies on Automobile Tyres], Yokohama Rubber Company ed., Sankaido, 15
April 1995, p. 7, etc.
2) “Gomu Kōgyō ni okeru Gijutsu Yosoku — Jidōsha taiya wo Chūshin ni shite [Technology Forecastingin the Rubber Industry: Focus on Automobile Tyres]”, Rubber Technology Forum, ed., (1990)
December, p. 35 – p. 43. Latter division of time periods considered with reference to “Kongo no
Taiya Gijutsu Yosoku [Future Tyre Technology Forecasting]”.
3) Gomu / Erasutomā to Mirai no Kōtsū [Rubbers / Elastomers and Future Transportation], Rubber
Technology Forum, ed., Gomutimes, March 2010, p. 69.

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2. Creation of the Tyre
Tyre

2.1. Beginnings as a Wheel
Tyres originally began as wheels. The origin of
the wheel is unclear, although it is thought tohave been at least 4,000 years ago. The use of

Rim or Felloe
Spoke

the wheel shows that it was at least known thatrolling results in less friction than sliding.

Fig. 2.3. Cart or Wagon Wheel 2)

Logs or round slices of logs were first used (Fig.
2.1). Gradually, these were replaced by discs

The steel rim that surrounds a railcar wheel andmade of several planks joined together (Fig.

comes in contact with the rail is called a tyre2.2), followed by spoked wheels (Fig. 2.3).

(Fig. 2.4).

Wagons were the main means of transportation
until automobiles became popular. Thesewagons had hubs of evergreen oak or elm, as
shown in Fig. 2.3; these were supported by
spokes encircled by a rim or felloe, while an

Retaining
Ring
RolledSteel Wheel
CentreTyre

Retaining
Ring Tyre

Cast Steel
Wheel
Centreiron band around the outside to prevent wearfrom contact with the ground could truly becalled a tyre.
Fig. 2.4. Railcar Wheel with Tyre 1)
Wheels have been used on vehicles (even the
Heian Period ox carriages) in completely
different time periods and completely different
countries. The vehicles from this time weremade of wood and probably did not offer muchin the way of riding comfort (Fig. 2.5) 3).
Fig. 2.1. Early Wooden Wagons 1)

Ox Carriage
Fig. 2.2. Various Improved Wheels 1)

Fig. 2.5. Heian Period Vehicle (Ox Carriage) 3)
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2.1.1. The Beginning of the Tyre
The discussion below draws heavily from Taiyano Hanashi [The Story of the Tyre] 1). Vehicles
with iron or wooden wheels were difficult topull on rough road surfaces. Accordingly, earlytyres were the result of various inventors
competing to somehow make vehicles travel
more comfortably. Attempts were made to give

Fig. 2.7. Benz Automobile Built in 1886

tyres greater elasticity; what is now known as(Replica)

the solid tyre (a tyre made wholly from rubber

Fitted with Solid Tyres (Toyota Automobile

with no air inside) was invented in 1835 (seeMuseum Collection) 4)

figures below).
2.2. History of the Tyre
The epoch-making invention of the time was
the pneumatic tyre. R. W. Thomson was thefirst to invent and patent the pneumatic tyre in
1845 (see Fig. 2.8).
Rivet

Elastic belt of
rubberised canvas

LeatherFig. 2.6. Various Early Solid Tyres 1)
Rim

The first automobile with a gasoline engine was
built

in

1886

by

GermanBolt

company

Daimler-Benz. Production of this vehicle
started in France in 1890. Although this vehicle
had solid rubber tyres, later automobile

Fig. 2.8. Thomson’s Pneumatic Carriage Tyre

manufacturers still used metal rings. In 1895,

Patented 1845 (UK) 5)

the first pneumatic tyre was developed for suchvehicles.

This was granted a UK patent 5) relating to an

A replica of the first Benz vehicle with solid

improvementtyres is on display at the Toyota Automobile

distinguishing feature of this invention was theMuseum (see Fig. 2.7).

elastic body around the wheel, which reducedincarriage

wheels.

The

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the running resistance and noise of the wheel
and improved the riding comfort, resulting in awheel that was also suitable for high-speed
applications such as steam vehicles. The elastic
body comprised a hollow belt made of a highmolecular substance such as rubber or gutta
percha (a type of natural rubber) and filled with
air.
Structurally, it was a pneumatic elastic belt of
rubberised canvas. Functionally, it worked on
the same principle as the tyres of today. It is

Fig. 2.9. The First Dunlop Tyre Pneumatic Tyre
9)

(Replica)

surprising to think that the same idea for themodern-day tyre existed over 160 years ago.

According to 100: The First Hundred Years ofThis tyre was made for horse-drawn carriages.

Pneumatic Tyres 1888-1988, J. B. Dunlop

Rubberised fabric was pasted together to form a

finally came up with this invention after

tube, which was riveted to a leather outer layer

repeated experiments because his ten-year-old

and also riveted to a wooden rim.

son, Johnny, had asked him to “make my

However, it was not very effective on actual

tricycle go easier and faster”.

vehicles and it was eventually forgotten. The

In his first experiment, Dunlop removed theactual tyre was invented by Dunlop in 1888,

solid rubber tyre from a tricycle wheel and tried

around 40 years after Thomson’s tyre. The idea

to roll it along, but it fell over mid-flight. Whenwas taken up by J. B. Dunlop and patented

Dunlop rolled his pneumatic tyre along with theagain. Dunlop’s patent was for a hollow tyre orsame force, it rolled across the garden, hit atube made of India rubber, fabric or other

door and rebounded. Having ridden a bicycle

suitable material filled with pressurised air andwith pneumatic tyres fitted, Johnny rated it very

fitted to a wheel by appropriate methods. As

highly (see Fig. 2.10).

shown in Fig. 2.9, Dunlop’s tyre comprised arubber tube encircling a thick wooden discabout 40cm in diameter, covered in rubberised
canvas with the ends nailed into the disc. Not
only did it improve the riding comfort, it alsosignificantly reduced the rolling resistancecompared to solid rubber tyres, making it run
more comfortably 9).

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bronze plaque at the site, which reads, “Thefirst pneumatic tyre factory in the world wasstarted here in 1889, to make tyres under John
Boyd Dunlop’s patent of the 7th December,
1888” 10). (Fig. 2.11)

Fig. 2.11. Bronze Plaque 10)
Following the emergence of pneumatic tyres,various efforts were put into making themeasier to use. One such initiative was to make it
Fig. 2.10. J. B. Dunlop with a Bicycle Fitted

easier to assemble and disassemble the tyre and6) 7)

rim; two methods were devised for this purpose.

with Pneumatic Tyres

His Son Johnny

The first was the wired-on (wire-type) method
2.2.1. Commercialisation of the Pneumaticdevised by C. K. Welch; the second was the

Tyreclincher (pull-on, Fig. 2.12) method devised by

Around this time, cycling was becoming aW. E. Bartlett. Both were granted patents inpopular sport. J. B. Dunlop’s pneumatic tyre1890. A valve was invented that allowed air toappeared just as cycling was beginning to growbe let out as well as pumped in; the patent for

in

was

this was granted to C. H. Woods in 1891. Not

entrepreneurs,

long after its establishment, The Pneumatic

publishers of cycling magazines, newspaper

Tyre and Booth’s Cycle Agency, Ltd. spent ajournalists and bicycle dealers alike joined

lot of money for the patent rights to these three

forces with Dunlop to commercialise theinventions, all of which contributed to thepneumatic tyre. In November 1889, The

expansion of the company 10). The wired-on

Pneumatic Tyre and Booth’s Cycle Agency,

method (Fig. 2.12), which used a ring of steel

Ltd. was established in Dublin, Ireland, withwire to affix the base of the carcass into the rim,

capital stock of ₤25,000. J. B. Dunlop

was the prototype for the modern-day method

transferred his patent rights to the company andof affixing automobile tyres to their rims 1).

popularity

epoch-making.

and

its

performanceSports-loving

became a company director. Today, there is a
12
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Wired-On Tyre

Clincher Tyre

Fig. 2.13. The First Horizontal Groove Pattern
Tyre, Made by Dunlop in 1905 6)

Fig. 2.12. Early Tyre Structures and Methods
for Attaching Them to Rims 1)

2.3. Rubber, an Essential Material for
Tyres

The Michelin brothers in France were the firstto use pneumatic tyres on an automobile. The

Without rubber, the modern-day pneumatic tyrestory is well-known how the brothers enteredwould not exist. Rubber is an essential material

and1,000km

for tyres. Natural rubber was the first type ofParis-Bordeaux-Paris automobile race in 1895,

rubber to be used in tyres; looking back, thereplacing their pneumatic tyres one after

discovery of natural rubber was the first step inanother. From then on, pneumatic tyres steadilytyre history.

somehow

completedtheadvanced into the field of automobiles.
However, the roads at the time were very

2.3.1. The History of Natural Rubbersmooth and the tyres had no tread pattern; with

Natural rubber has long served humankind; ofa little speed built up, a vehicle could not be

all the types of rubber, it is still the best source

easily stopped. Tyres also often sufferedmaterial. The history of natural rubber ispunctures

10).

outlined below.

The Dunlop Company in the United Kingdom

In the mid-1490s, Christopher Columbus saw

put the first tread on a tyre in 1905, a simple

the indigenous people of Hispaniola (Haiti) inhorizontal groove pattern. This was produced

the West Indies playing with a rubber ball.

by placing short iron rods on the unvulcanized

Following the discovery of the New World, therubber; the vulcanizing temperature would

properties of natural rubber, such as its

imprint the pattern into the rubbershown in Fig. 2.13.

6). This iselasticity and water resistance, were noted andstudies began on its uses. However, until C.
Goodyear discovered the use of sulphur tovulcanise rubber in 1839, rubber was simply arare commodity and served no purpose as anindustrial raw material. The discovery of
13

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vulcanisation enabled the development of the

In light of such circumstances, improvements

rubber industry. Coupled with the emergence ofwere made to natural rubber. Efforts began inthand 20

Malaysia – the world’s largest producer ofcenturies, this formed the basis for thenatural rubber at the time – and other countries

modern-day industry. Research on natural

to systematically replant with higher-yieldrubber continued in the 19th century, with M.

species to increase yields, improve tapping

Faraday confirming the chemical composition

methods (extracting rubber latex by cutting theof natural rubber as C5H8 in 1826. In 1860, G.

tree trunk), use latex secretion promoters, prune

Williams dry-distilled rubber and isolated thetrees while young, fertilise, carry out soil

isoprene monomer 8).

management

the automotive industry in the 19

Rubberlater

prevent

disease.

Rationalisation and centralisation of raw rubber

consumption with the growth of the automotive

production processes meant improved quality

industry. Since the United Kingdom had theand reduced costs, all of which combined tomonopoly on 80% of the world’s cultivatedprovide competition against synthetic rubber.

rubber, other countries struggled to secure raw

Some attempts were made to catch up to

rubber.

synthetic rubber through chemical modification

Later, rubber became an essential militaryof natural rubber and development of newcommodity in the World Wars. Full-scale

forms of natural rubber 8). Currently, naturalresearch on synthetic rubber as a strategic

rubber is very highly priced, with a strong

resource was carried out around the time of thedemand for it in emerging nations.

First World War (1914). Until the Second

The natural rubber tree used industrially is the

World

mass

Pará rubber tree Hevea brasiliensis, which has

production of synthetic rubber, other countries

very low non-rubber content and a very higharound the world were unable to break theyield

United Kingdom’s monopoly.

cis-1.4-polyisoprene. The latex extracted when

During the First and Second World Wars, thethe bark is cut has a 30% rubber content. This

industrialisation of butadiene synthetic rubber

rubber content contains proteins and small

was fast-tracked because it was necessary toamounts of lipids,

ensure vast amounts of rubber for military

sugars and ash. Although the latex remains

manoeuvres. After the wars, synthetic rubber

stable while inside the rubber tree, once

proved to be a worthy competitor to natural

harvested it is prone to spontaneous coagulation

rubber, with improvement to the quality anddue to enzyme action, so a protectant like

reduction in the cost of SBR as well as theammonia is added to prevent coagulation. The

development of the petrochemical industry; inlatex is a milky juice in the ductal tissue that

1963, worldwide synthetic rubber consumption

develops near the cambium layer within the

finally overtook that of natural rubber.

Hevea tree, extracted by cutting the bark

(1939-45)

increased

and

in

War

dramaticallythpromptedofrubberhydrocarbons,namely14
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(tapping) of trees that are at least 5-7 years old.

2.4.1. Why Does Rubber Stretch?

The latex coagulates when acid is added to it.

If it were not for a unique elastic material such

The dried form of this is known as raw or crude

as rubber that can bounce, stretch and springrubber.

back, there would be no tyres.

Hevea rubber is polyisoprene with a 1.4-cis

Let us consider the structure of rubber.

structure and has very high tensile strength. It

Unlike other materials, rubber stretches when

crystallises when stretched and usually has highpulled and instantly springs back when released.

mechanical strength, low heat resistance and

It is also elastic and bounces. Why does rubber

high abrasion resistance. Accordingly, it has ahave such properties? After much research, thehigh use ratio in high-load tyres.

following are currently thought to hold true.

Natural rubber, discovered and improved by

1) Rubber molecules themselves are shaped

humans, is a high-quality rubber with superior

like springs. When subjected to somephysical properties that has led to the formation

deformation, such as pulling, they areof a wide range of industrial fields. The

subjected to stress from changes in shape,

properties of natural rubber, such as its highsuch as when a spring is pulled (this calledstrength and low heat build-up, make it perfectentropic elasticity). Even where there is nofor tyres and it has been a key component in the

direct force on the molecules, they aredevelopment of the modern tyre industry.

subjected to force from the change in shape.
2) Such behaviour means that rubber molecules

2.4. The Importance of the Physicalhave gas-like properties and the so-called

Properties of Rubber

gas-like molecules form a polymer structure.
Fig. 2.14 shows model
Rubber Elasticity

Natural rubber
molecules(cis-polyisoprene)

cis form (rounded)
Forms a spring

Pull
Cross-linking point

Rubber molecules

Trans form(linear)
Does not form aspring

Pull
Cross-linking point

Spring-shaped molecules deform instructure when pulled
Cross-linking point

Cross-linking point

Fig. 2.14. Structural Model of Natural Rubber
15
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2.4.2. The Discovery of Vulcanisation

phenomenon. A standard test in the rubber

The elasticity of rubber cannot be achieved byindustry is to apply torsional deformation torubberrequiressulphur-added unvulcanised rubber over heat

vulcanisation. This discovery by Goodyear inand to measure the corresponding force

1939 was the most important discovery in the(torque) and the increased rigidity over time.

history of rubber. Vulcanisation is the process

When this reaches a certain level (plateau),of causing rubber molecules to bond together

vulcanisationis(in many cases the cross-linking is achieved byaccelerators

significantly

sulphur). The vulcanisation reaction causes

vulcanisation time. Quicker vulcanisation has

adjoining molecules to bond together and form

been a major issue in the rubber industry,a network; any stress to any part of the network

particularly for tyres. Since natural rubber inis transmitted to the entire network, which

particular deteriorates when exposed to heat, ademonstrates rubber elasticity; in other words,

major question has been how to complete theit has turned into rubber. Fig. 2.15 clarifies thisvulcanisation in a shorter amount of time.

molecules

alone;

it

Cross-linking pointcomplete.

Vulcanisation
reducethe

Cross-linking point
Rubbermolecules
Sulphur

Vulcanisation curve
HardenWith vulcanisation accelerator

TorqueWithout vulcanisation accelerator

Vulcanisation time
Fig. 2.15. Vulcanisation and Vulcanisation Curve

16
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2.5. Natural Rubber and Environmental

time being. With other emerging nations

Issuescoming onto the scene, the price of natural
rubber will probably continue to soar for someAs environmental issues have intensified in thesttime yet. Conversely, there may be a shortage

21 century, natural rubber has been seen asof natural rubber as a raw material.

carbon neutral and there has been an increase in

The properties of natural rubber can change

its use.

significantly when epoxy-modified. Recent

In the 2010s, it is thought that the strong

research has examined new scopes of usage fordemand for natural rubber by emerging nations

it; accordingly, it is expected to continue tosuch as China and India will continue for the

expand in use 10) 11)

Cited references:
1) Hattori, Rokuro: Taiya no Hanashi [The Story of the Tyre], Taiseisha, 25 June 1992, pp. 2-3.
2) Watanabe, Tetsuo: Taiya no O-Hanashi [The Story of the Tyre], October 2002, Japan Standards Association, p. 13,
cited from Ichimura, Yoshio: Jidōsha Kōgaku Zensho [Automotive Engineering Compendium], (1980) Vol. 10,
Chapter 3, Sankaido, p. 170.
3) Shin Sōgō Zusetsu Kokugo [New Comprehensive Illustrated Language], Tokyo Shoseki, 2004, p. 21.
4) “Toyota Automobile Museum” Collection, 41-100 Yokomichi, Nagakute, Aichi.
5) UK Patent No. 10990.
6) 100: The First Hundred Years of Pneumatic Tyres 1888-1988, Sumitomo Rubber Industries, Ltd., p. 7.
7) Best Car, ed., Taiya no Subete ga Wakaru Hon [The Book that Tells You Everything You Need to Know About
Tyres], Sansuisha, Kodansha, 2008, p. 95.
8) Gomu Kōgyō Binran [Rubber Industry Handbook], 4th Edition, The Society of Rubber Science and Technology,
Japan, 20 January 1994, pp. 179-182.
9) Watanabe, Tetsuo: Taiya no O-Hanashi [The Story of the Tyre], October 2002, Japan Standards Association, p. 17,
cited from Bridgestone Corporation Public Relations Department (1987): Taiya Hyakka [Tyre Encyclopaedia], p.
15, Toyo Keizai, Inc.
10) Sumitomo Gomu Hyakunen-shi [Hundred-year History of Sumitomo Rubber], Sumitomo Rubber Industries, Ltd.,
December 2009, pp. 33-35.
11) Tokushu Erasutomā no Mirai Tenkai o Saguru Part I [Exploring Future Development of Special Elastomers PartI], Rubber Technology Forum, ed., Gomutimes, pp. 21-22, 1992, and Laid-Open Patent No. 2000-169504:
Sumitomo Rubber Industries, Ltd., Kao Co., Ltd., Fuji Latex Co., Ltd., and Higashi Kagaku, Co., Ltd.

17
National Museum of Nature and Science
Vol.16,2011

3. Dawn of the Japanese Rubber Industry (The Age of Early Compounding
Techniques)3.1. Meiji Period – Early Taisho Period

the foundation of the modern rubber industry inJapan, at least technically speaking. This was

As mentioned in the previous chapters,

around 50 years after Goodyear’s discovery ofJapanese tyre production started at the end of

vulcanisation 3) 2).

the Meiji Period (initially bicycle and rickshaw

In this era of compound-focused development,tyres; the first automobile tyres were produced

experimentation was carried out on rubberin the second year of the Taisho Period, 1913).

compounds and many compounding specialists

The core technologies at the time were rubber

emerged,compounding and vulcanisation. Let us now

compounding. The compounds were kept secret,address the rubber technology of the day.

technical knowledge was monopolised and they

The rubber industry was just dawning at thereceived higher salaries than factory managers.

time; rubber compounding and vulcanisation

This continued until around the end of thewere being developed independently throughTaishotrial and error.

drastically with the invention of organic

having

Period.

masteredThethetechnology

art

of

changedvulcanisation accelerators. Before there were
3.1.1. Late Meiji Rubber Technology

organic vulcanisation accelerators, the mostThe

important issue was how to combine inorganic

Japan

RubberBall

Factory(Nihon

Gomudama Seizōzyo) (or more correctly, thevulcanisation

agentswithJapan Rubber Factory(Nihon Gomu Seizōzyo),vulcanisation accelerators.

according to Hyōgo Gomu Kōgyō-shi [History

Let us now examine compounding techniques.

of the Hyogo Rubber Industry]; author note) isThis discussion draws heavily from Yamada,said to have been established in Kobe in 1885,

Hitoshi:manufacturing balls and pillows (Kōbe Kaikō

Specialists]”,

Haigō

Sanjū-nen-shi [Thirty-Year History of the[Compounding

Techniques],

Opening of Kobe Port], published 1898) 3).

Techniques

However, it is generally said that the JapaneseSociety of Rubber Science and Technology,

rubber industry began in 1886. Namely, theJapan, ed.) 1). (Hitoshi Yamada is a chief

Tsuchiya Rubber Factory (later the Mitatsuchi

examiner for the Compounding Techniques

Rubber Manufacturing Partnership(Mitatsuchi

Research

Gomu Seizō Gōmēgaisya)) was established at

Rubber Science and Technology, Japan and has

the end of that year, moving on from repairing

researched these compounding specialists inpersonal diving costumes to successfully

depth; the author is also a member of thevulcanising rubber. Accordingly, this formed

Subcommittee.)“Haigō-Shi

Research

inorganic[CompoundingnoTatekata
Compounding

Subcommittee,

Subcommittee,

The

Society

The

of

18
National Museum of Nature and Science
Vol.16,2011

As mentioned previously, the Japanese rubber

businesses started operating 4) 11). The industry

industry is generally said to have started instarted growing in Japan in the 1890s; in 1894,

1886 with the establishment of the Tsuchiya

theRubber Factory. The Tsuchiya Rubber Factory

vulcanisation technology, established a rubberchanged its name to Mitatsuchi Rubber

firm in Kobe 4-7) 11) 12). In 1896, the Tokyo

Manufacturing Partnership in 1892. Mitatsuchi

Rubber Factory(Tokyo Gomu Seisakuzyo) was

merged with Showa Rubber Co., Ltd. in 1945.

launched,

Yoshidabrothers,

as

was

the

who

had

Yoshidacold

Rubber

Factory(Yoshida Gomu Seizō), founded by(1) Early Technology (Mitatsuchi Technology)

former Mitatsuchi employees

Despite reference to original documentation,Works(Hirano Seizōzyo)early attempts at vulcanisation by Mitatsuchi

Rubber(Fujikura Gomu)

resulted in a series of failures with no specificthe same time.

method of vulcanisation attained

15)

.

19)

18)

4) 9)

. Hiranoand Fujikura

also started around

Although rubber factories were opening acrossFollowing much trial and error, researchers

the country, these were home-based businesses

settled on a type of heated-stone method used8) 9)

for roasting sweet potatoes. The final methodfactories nationwide that employed ten or more

adopted was a unique vulcanisation method in

regular staff members. Even by around 1909,

which unvulcanised rubber was buried in athere were no more than 19 factories that

container of small stones and sand andemployed five or more staff members 4) 5) 8) 13).

gradually heated to produce even vulcanisation

At the end of 1907, the three major companies4) 5) 9) 15)

in Tokyo Prefecture were Mitatsuchi with 229. This was also adopted by other4) 11) 16). In 1900, there were only two rubber. Various

employees, Meiji Rubber with 140 and Japan

compounds were used, such as adding lime or

Rubber with 100 4) 12). Mitatsuchi had held alitharge (lead oxide; PbO) 15). During mixing,

near monopoly in the rubber industry for ten

the natural rubber was cut with scissors, soaked

years until Meiji Rubber was founded 4) 9) 10) 14).

in volatile oil until swollen, then transferred to

All rubber shops sought out Mitatsuchi’s

companies in 1904-1905

a roller or mortar

4) 5) 17). It then had to becompound14). This suggests a relationshippounded continuously with a pestle for several

between the compounding specialists andhours and workers are said to have become

Mitatsuchi.

intoxicated from the volatile oil 15).
3.1.2. The Rubber Industry at the End ofth

the 19Century and Start of the 20thCentury

3.2. The Rubber Industry in the Late Meiji
Period (Start of the Tyre Industry; authornote)

A few years after Mitatsuchi was established(from 1888 onwards), several rubber seal

The British-funded Japan Ingram Rubber
19

National Museum of Nature and Science
Vol.16,2011

Company (hereinafter abbreviated as ‘Ingram’)based on Gomu Haigō Kokinshū [Collection of

was founded in 1908, while the Dunlop Rubber

Rubber Compounds Old and New], publishedCompany (Far East) (now Sumitomo Rubber

in 1940, although it is not clear if they were

Industries; hereinafter abbreviated as ‘Dunlop’)

used in the late Meiji Period. A fixed natural

was founded in 19094-7) 9) 11-13). Both had thesame capital system; Ingram merged into
Dunlop in 19114-7) 9) 11) 12).

rubber content is characteristic of Dunlop 2).
A significant amount of Mitatsuchi compounds
were versions of Dunlop compounds, giving an

Bicycles grew in popularity from around 1907,

Oriental take on the British rubber compounds.

precipitating a sudden rise in demand for tyres

Mitatsuchi quietly built up its compounding4) 5) 9-12). There was an increased demand fortechniques and slipped in to take the reins ofrickshaw tyres as well; companies leapt into

the Japanese rubber compounding domain

production. Mitatsuchi and Meiji Rubber madealongside Dunlop. The two of them dominatedprototypes in the early 1900s, launching intofrom 1897 to the early Taisho Period and werefull-scale production around 1908 4) 5) 9).

still

The

achievements in the early Showa Period 14).

Japaneserubberindustry

followedmakinganumberofnoteworthy

contemporary trends and gradually built up its
capabilities by imitating the technology of
Dunlop and Ingram.

3.3. The Rubber Industry from the Late
Meiji Period to the Early Taisho Period

3.2.1. Dunlop
Dunlop had the best technologies and facilities

In the late Meiji Period, the Japanese rubberwith large amounts of capital provided byindustry

Dunlop in the United Kingdom. According toremained in an embryonic stage. Rather than an

Nihon Gomu Kōgyō-shi [The History of theacademic

Japanese Rubber Industry], “the Dunlop

chemicals and persisting with sulphur, thefactory was also called the rubber school”, withmixing of which was a closely guarded secret atmany engineers passing through its doors andeach factory” (discussion with Masanosuke

acquiredsome

discipline,ittechnology,
involvedbut“usingplaying active roles in other rubber companies

Sasabe of Bando Chemical Industries). There4) 5) 7) 12). The rapid spread of technology such aswere no testing facilities; compounding relied

Dunlop Rubber’s “compounding” techniques ison experience and intuition. However, eachsaid to be one reason why so many rubbercompany kept their compounds a secret while

factories were established in Kobe 4) 5) 9).

each trying to work out

3.2.2. Changes to Tyre Compounds

3.3.1.

Dunlop/Mitatsuchi Compounds

Specialists

Dunlop compounds are shown in Table 3.1,

The Rubber Industry in the Late Taisho Period

The

Rise

of

Compounding

20
National Museum of Nature and Science
Vol.16,2011

The idea of compound secrecy continued after
the Meiji Period

20), with rubber product3.3.2. The World of the Compounding
Specialists

manufacturers keeping their compound recipes

Compounding specialists had an apprenticeshiplocked away in vaults like valuables. It was not

system. Novices would work for a specialist foreasy for new materials to gain acceptance.

aroundIn the early Taisho Period, Sōichirō Tanaka

memorising formulations 5). Nonetheless, there(trans.) published Kōgyō Gomu Kagaku [Thewere many studious compounding specialists.

Chemistry of Industrial Rubber]. This work

The compounding formulations were of course

outlined manufacturing methods in detail, as

kept secret by the specialists and were never towell as vulcanisation theory and testing andbe taught to workers within the factory 5).

analysis methods 21) and was majorly utilised

These flourishing compounding specialists

by rubber engineers 4). However, although thiswere later put out of business by thewasacademic

introduction of vulcanisation accelerators. Let

investigation, many factories still relied on the

us examine the changes to compounds from thesecrets held by compounding specialists.

Meiji Period on.

thepartialbeginning

of

five

years

for

almostnopay,

Table 3.1. Dunlop Automobile Tyre Compounds
Ribbed smoked (natural rubber)

72

Ribbed smoked (natural rubber)

79

Reclaimed (recycled rubber)

56

Reclaimed (recycled rubber)

42

Zinc oxide (ZnO)

26

Calcium carbonate (heavy)

47

Calcium carbonate (heavy)

26

Carbon black5

Flower of sulphur

21

Deacidified sulphur

11

Rubber powder

15

Litharge (PbO)

11

Litharge (PbO)

5

Mineral rubber (pitch, asphalt)

8

Mineral rubber (pitch, asphalt)

8

Caustic magnesia

3

Pale machine oil

15

Pale machine oil

16

Quicklime

5

Pine resin

5

Vulcanizing time

40min

Vulcanizing time

60min

(Dunlop compound specialist compound presumed to be from the Taisho Period. Unclear whether or
not it is Dunlop; Yamada comment. Compound features multiple inorganic vulcanisation
accelerators; author note)

21
National Museum of Nature and Science
Vol.16,2011

3.4. Compounding Agents from the End ofused, under names such as whitening, calcium

the Meiji Period to the Taisho Periodcarbonate or coal stone. While light calcium
carbonate was first mass produced in 1919 by

Matsutarō Hanaki states the following9) 23).

Shiraishi Kogyo, its value was not appreciated“At that time, Meiji Rubber and Toyo Rubber

for quite some time afterwards. However, thishad mostly the same rubber compounding

was gradually recognised through research at

agents, with the most important being sulphur

theor slaked lime as an accelerant. Other agentsŌsaka Shikenzyo) ; by the early Showa Period,

used included zinc oxide (ZnO), sedimentary

it had become a major rubber chemicalcalcium carbonate, magnesium carbonate, withalongside zinc oxide and magnesium carbonate

browning achieved by a mix of burnt-pine ink

4) 20)or lamp soot for black and red iron oxide for

Fatty-acid-soap

red, and golden antimony sulphide.”carbonate was also developed in the early

Several compounding agents are describedShowa

below.

underappreciated to begin with, it made a(i) Zinc Oxide (ZnO)

significant contribution to the field of rubber

Zinc oxide was the most commonly usedcompounding once research at the University ofreinforcing agent in the Meiji Period. It was

Akron demonstrated its superiority as areplaced by calcium carbonate and carbon in

reinforcing filler for rubber 20).

the late Taisho to early Showa Period. As(iv) Carbon Black

organic accelerators grew in popularity from

Imported since 1901, it was first used as a

the end of the Taisho Period, more modern

colourant. It grew in popularity as a reinforcing

accelerators began to be more widely used 4).

agent for tyres from the end of the Taisho(ii) Basic Magnesium Carbonate

Period and was being produced domestically in

Various chemical formulations of compounding

1931 4).

agents,such

3MgCO3·Mg(OH)2·3H2O,

as

4MgCO3·Mg(OH)2·5H2O,

National

Osaka

Laboratory(Kokuritsu.

Period.

surface-treated
While

this,

calciumtoo,was(v) Accelerators

andInitially, “the three most important accelerators

calledin compounds were slaked lime, litharge andmagnesium carbonate or light magnesium

magnesia; it took experience to use these

5MgCO3·2Mg(OH)2·5H2O,

were1) 4) 8) 24). These were first used inproperly” (discussion with Tetsunosuke Mori,rubber in 1918 and were used in most rubber

formerly of Kakuichi Rubber) 4). This was the

products by the end of the late Taisho to earlyreason that rubber compounding was thought toShowa Period 4).

be difficult and kept secret 25). “Following a(iii) Calcium Carbonate

visit by a British compounding specialist toInitially, heavy calcium carbonate was often

Meiji Rubber, other compounds were known

carbonate

22
National Museum of Nature and Science
Vol.16,2011

about,but

only

quicklime(discussion

withHanaki)

was
23)

.

used”

Inorganiccited in the literature (Gomu Haigō-hō:
Fukuoka,Harutarō

1922[Rubberchemicals such as sodium silicate were also

Compounding Methods: Harutaro Fukuoka

used as kinds of accelerators, but were not1922])

called accelerators

4) 23)

.

in

Gomu

Compounding Methods]

Haigō-hō[Rubber26), published in 1922,

The spread of organic accelerators in Japan can

and a ‘Mitatsuchi-style’ compound are shown

be pinpointed to this time period, with somein Tables 3.2 and 3.3.

factories starting to use them from this time on.
Table
3.5. The Rubber Industry in the Late Taisho

3.2.

Samplepossible to produce clear rubber, as well as
improvements in the physical properties of therubber. By the late Taisho Period, there had
been significant development in the productionof rubber boots from these rubber compounds;
these were even being exported overseas 4) 5).
From the manufacturing perspective, there was

Tyre

Compounds 26) 14)

PeriodThe use of magnesium carbonate made it

Automobile
Fukuoka

Mitatsuchi

Ribbed smoked (natural
rubber)100

100

Magnesium carbonate

21

23

Brown factice(softening agent,
processing agent)
Carbon black

9

9

4

5

Deacidified sulphur

44Paraffin

3

3

Caustic magnesia

4

3

Vulcanizing time

50 min50 mina division of labour between vulcanisation andproduction, with mixing factories carrying out

Table

compounding and simple vulcanisation, while

Compounds 26) 14)

3.3.

Sampleproduction factories carried out production 4) 5).
The preface to Gomu Haigō-hō [Rubber
Compounding Methods], published in 1922,
provides an insight into the state of the rubber
industry at the time. “Manufacturing methods,
particularly compounding methods, are kept
completely secret; there are many people whohave worked in production for many years anddo not even know the components of theirproducts.” This suggests the presence ofAutomobile

Tyre

Fukuoka

Mitatsuchi

Ribbed smoked(natural rubber)
Zinc oxide (ZnO)

100

100

29

29

Magnesium
carbonate
Deacidified
sulphur
Litharge (PbO)

18

18

5

5

7

7

Carbon black4

4

Mineral rubber

5

5

Vulcanizing time

60 min

120 minFukuoka:Gomu Haigō-hō [Rubbercompounding specialists.
For comparative reference between two typicalcompounds of the time, the sample compound

Compounding Methods],
23

National Museum of Nature and Science
Vol.16,2011

Mitatsuchi:

Fukuoka, Harutaro (1922)[Studies in Rubber] 29) published in 1926.

Gomu Haigō Kokinshū

Gomu Seizō Kagaku [The Chemistry of Rubber[Collection of Rubber

Manufacturing] was a publication by Waseda

Compounds Old and New]

University; Gomu no Kenkyū [Studies in

14)

Rubber] was a book based on lectures at(1940)

Tohoku, Moriyama, Tokichirō

Imperial

University.

Asample(Compounds presumed to be from the early tocompound from Gomu Seizō Kagaku [Themid-Taisho Period; Yamada comment)

Chemistry of Rubber Manufacturing] is shownin Table 3.4.

The two tables show that the compound
recordedin

Gomu

Haigō-hō[Rubber

Compounding Methods] published in 1922 is

Table 3.4. Sample Automobile Tyre
Compounds 28)

almost identical to the ‘Mitatsuchi-style’Pará (wild rubber)

40

Caucho (wild rubber)27

sources show the compounding amounts inUpper Congo27

terms of weight used, given in the tables as

Reclaimed

13

parts per hundred rubber). Since early rubber

Zinc oxide (ZnO)

17

compounds were more complex, these sample

Lime

1

compounds were probably a simplified version

Sulphur

9

compound cited in the literature

14)

(both

used for a public lecture. Literature published(Compounds presumed to be from the latein 1943 states that “complex formulations were

Meiji to early Taisho Periods; Yamada

effective for keeping compounds a secret, butcomment)

nothing

Upper Congo; unclear but probably wild rubber

more,”

while

anothersourceconjectured that compounding specialists added8)

in unnecessary raw materials to make it

Gomu Seizō Kagaku [The Chemistry of Rubber

needlessly complicated so that the compounds

Manufacturing] has a detailed record on

could not be easily learned

27). The parts per

hundred rubber (phr) representation indicatesvulcanisation accelerators; Table 3.5 shows thechanges in sample compounds 28).

the weight of other compounding agents inproportion to 100 parts (weight) of natural
rubber.
It seems that progress had been made on the
research/education front by the late Taisho
Period,with

Chemistryof

Gomu
RubberSeizō

KagakuManufacturing]

[The
28)

published in 1924 and Gomu no Kenkyū

Table 3.5. Changes in Tyre Tread Compounds
1) 4) 8)24
National Museum of Nature and Science
Vol.16,2011

Reinforcing agent : zinc flower
Colourant : lamp black
Accelerators : slaked lime, magnesia,
anilineprogressed with compounding specialists at the

1918

Carbon black and accelerators appear

speed; the vulcanization accelerators of the day

1933

Carbon black and accelerators
become popular
Vulcanisation time reduces due toaccelerator combination
Effectiveness of anti-ageing agents
becomes clear

1912(Meiji~Taisho)core.
The central technology was vulcanization
were

inorganic

vulcanization

accelerators.

Vulcanization time could be adjusted throughproficient use of vulcanization accelerators;
accordingly, these accelerators were the mostGenerally speaking, the amount of rubber

importantincreased while the amount of sulphur

specialists had. The discovery of organic

decreased.

vulcanization

technology

thecompounding

accelerators

reducedthevulcanization time even further and it was
Automobile tyre compounds had reached thetheorised that the vulcanization phenomenon

highest level of technology available at thewas an organic reaction. Thus, there was atime.

transition from a secret technology formulated
by compounding specialists using complex

3.5.1.

PopularisationofVulcanisation

inorganic

accelerators

toatheoretical

Accelerators

technology; the world of rubber compounds(1) Inorganic Accelerators

gradually transitioned from the domain of

While metal oxides such as slaked lime andcompound specialists to the domain of organic

magnesia had been used as vulcanisation

chemistry, making the compound specialists

accelerators in the Meiji Period, the new

obsolete.

inorganic accelerator developed by Matsutarō

Compounds

Hanaki in the early Taisho Period was a fired

fundamentallybasic lead carbonate and was promoted incompounds of today.

from

this

simplified,

time

on

becamecloser

to

the

of

Organic

1918-19. It is said to have been developed
following repeated research and analysis on

3.5.2.

compounds imported from the United States.

Accelerators

Since Goodyear used basic lead carbonate as an

While the timing of the popularisation ofaccelerator, this is said to be related technology

organic accelerators in Japan cannot be

30).

Popularisation

precisely defined due to differing accounts

This had the effect of reducing the vulcanising

between factories, it was after 1920, at the end

time from 1-3 hours to 15 minutes.

of the Taisho Period or start of the Showa
Period 1) 4) 14) 23) 31). It is very likely to have been(2) Organic Accelerators
Compound-focusedfrom around 1920, as George Oenschlager
rubbertechnology(who discovered organic accelerators) is said to25

National Museum of Nature and Science
Vol.16,2011

have visited Yokohama Rubber in 1919 andhuge impact. Since all-purpose inorganic

passed on some cutting-edge compounding

accelerator

techniques4) 23).

compounds

had

a

long

vulcanization time, a large number of metal

New compounds based on organic accelerators

moulds had to be set up for mass production.

werelaboratory

Despite organic accelerators having a shorter

employees and researchers as “compounds that

vulcanisation time, they would mean that theapply scientific principles”, but were generally

substantial investment that went into these

not used in practice 14). This is because themetal moulds would have gone to waste. This

Japanese rubber industry at the time wasfactor, combined with apprehension about thelargely dominated by the Mitatsuchi andeffectiveness of the new accelerators, resulted

Dunlop schools and researchers could not

in many factories putting off introducing the

become active enough under that influence.

new

Many engineers in the Mitatsuchi and Dunlop

earthquake, the metal moulds had to be rebuilt;

schools in the late Taisho Period did not know

this resulted in a growing trend towards using

about changes in formulation, believing theorganic accelerators 22) 23).

idea that rubber would become brittle if

Despite some twists and turns along the way,

adoptedbyaccelerators were usedindustrial4) 14).

accelerators.

organic

However,

accelerators

grew

due

in

to

the

popularity,

Many would say that the expensive organic

resultingaccelerators are useless, and that lime wasvulcanization time and improved productenough 23). Many rubber companies at the timequality 4).

inadramatic

reductioninhad no testing equipment and no confidence inusing new compounding agents. However, once

3.5.3. Disclosure of Compounds

Japan Rubber, which had good testing facilities,

In the early Showa Period, information onplaced a substantial order, it immediately began

compounds was beginning to be made available

4)

to be used .

to the public. When Heisen Yoko established

Meanwhile, Mitatsuchi – arguably the motherits affiliated rubber laboratory in 1928, it wasof the compounding specialists, Meiji Rubber,completely open to the industry 4) 22) 23) 32). The

Furukawa, Fujikura and other companies

monthly

started importing or producing their own

published and distributed to factories fromaccelerators from the end of the Taisho Period

1933 onwards, explaining how to use chemicals

14). By some accounts, some had been using

and providing data on accelerators 4) 5) 32).

these since the end of the Meiji Period or start

Dunlop also began inviting British engineers toof the Taisho Period; several other companies

provide open lectures on basic compounds inwere secretly using organic accelerators 4) 8) 14)

the early Showa Period 4). Prior to this, the23)

Ministry

The Great Kanto Earthquake of 1923 had aTransportation had published the results of tests.

magazineof

Gomu[Rubber]

Communications

was

and

26
National Museum of Nature and Science
Vol.16,2011

on accelerators in 1924 4).

Fig. 3.1. Vulcanisation Mechanism by means ofan Inorganic Vulcanization Accelerator

3.5.4. The Fate of the Compounding
Specialists
Thus,

as

(2) Organic Vulcanization Acceleratorsorganic

accelerators

grew

in

Let us now describe the mechanism of action of

popularity, the rubber industry underwent anorganic

vulcanization

epoch-making transition from an alchemical(2-Mercaptobenzothiazole), still in use today.

stage with secret mixtures made compounding

Vulcanization accelerators act as a catalyst for

specialists to a modern industry based ona sulphur cross-linking reaction. At this point,science and technology.

theThere was also an increase in so-called

accelerator and zinc oxide is essential. Both are

educated engineers.

necessary; without either of them, vulcanization

Consequently, the revolution in compounding

would not work. The reaction formula is given

due to organic accelerators and the emergencein Fig. 3.2.

of orthodox-educated engineers spelled the end

Sulphur chains are trapped between MBT

for the compounding specialists.

(reactions 1-2). The sulphur breaks down

reaction

betweenaccelerator

the

MBT

vulcanization

within the sulphur chains and reacts with the
3.5.5. Comparison of the Mechanisms ofrubber molecules (reactions 3-4). A reaction

Inorganic

takes places between the sulphur and theandOrganic

Vulcanisation

Accelerators

molecules and cross-linking is established(1) Inorganic Vulcanization Accelerators(reaction 5) 27).

As mentioned previously, during the age of
inorganic vulcanization accelerators, metal

3.6. The Rubber Industry in the First Half ofoxides such as litharge (lead oxide; PbO) or

the Showa Period

zinc oxide (ZnO) were used in addition tovarious other kinds of compounding agents.

Let us now outline the state of the rubber

The use of metal oxides also required the use ofindustry in the early Showa Period.

organic acids, such as oleic acid or stearic acid.
The reaction formula below (Fig. 3.1) shows

3.6.1. The Rubber Industry in the Early

the cross-linking reaction mechanism between

Showa Periodorganic acid and PbO. The Pb forms a metallic(1) Use of Organic Accelerators

soap, which makes a polysulphide, releasing

While organic accelerators gained popularity

active sulphur and accelerates vulcanization34).

considerably at the end of the Taisho and startof the Showa Period, it appears that they were
not readily mastered. Even a source publishedin 1940 14) notes that accelerators were used in
27

National Museum of Nature and Science
Vol.16,2011

token small amounts and not very effectively.
Furthermore, small amounts of accelerators
made the rubber harder to scorch (burn;prevulcanization) and easier to extrude; somecompounds were researched out to that end 14).
Research divisions of major factories used an
academic

approach

to

come

up

with

compounds. Ninety per cent of smaller
factories used the old methods of secretly
stealing, memorising or otherwise learningcompounds 33).
(2) The “Academic” Movement
However, the academic initiatives appeared tobe reliable and The Society of Rubber Scienceand Technology, Japan was established in 1928.
Gomu

Seizō-Hō[Rubber

Manufacturing

Methods] recorded basic sample compounds,
such as those given in Table 3.6, that are stillused today.
While research on compounds progressed, theaforementioned

Gomu

Manufacturing Methods]

Seizō-Hō25)[Rubberalso recorded

sample compounds for automobile tyres, suchas those given in Table 3.7, that are still used
today.

28
National Museum of Nature and Science
Vol.16,2011

1) Generation of ZnMBT [I] by reaction between vulcanisation accelerator MBT and zinc oxide(ZnO)2) Reaction between ZnMBT and Sulphur (Sxy)3) Reaction with rubber(Regeneration of MBT)

4) Sx-Sy separation through coordination of Zn+ ions

(Advances to cross-linking)(Reaction with rubber, advances to cross-linking
precursors)5) Generation of cross-links and cross-linking precursors(Cross-linking precursor)(Cross-links)

Further cross-linking continues

Fig. 3.2. Mechanism of Action of Vulcanisation Accelerator MBT 27)

29
National Museum of Nature and Science
Vol.16,2011

Table 3.6. Basic Compound from Gomu

aforementioned MBT.

Seizō-Hō [Rubber Manufacturing Methods](Refer to) modern compound samples (natural

Raw Rubber

100

rubber tyres)

Sulphur

0.5-3.5

Natural rubber 100, zinc oxide (ZnO) 5, stearic

Accelerator

0.5-1.5

acid 1-2, carbon black 50-60, anti-ageing agent

Zinc oxide (ZnO)

1.0-101, oil 1-5, sulphur 1-2, vulcanisation accelerator

Stearic acid0.5-2

(NS or CZ) 1-2.

Anti-ageing agent

0.25-1.5

NS: N-Oxydiethylene-2-benzothiazole
sulfenamide

Other, reinforcing agent (carbon black,

CZ: N-cyclohexyle-2-benzothiazole

magnesium carbonate, clay)

sulfenamide

Filler, softener, colourant
3.7 Summary

Table 3.7. Automobile Tyre Compound
Smoked sheet (natural rubber)

100

Mineral rubber

5

Carbon black

40

Zinc oxide (ZnO)

5

Stearic acid1

Binder1

Anti-ageing agent

1

DM (organic vulcanisation accelerator)

0.8

Sulphur3(Probably an early Showa Period compound;
Yamada comment)
Here, an accelerator is used in an actual
compound for automobile tyres. The compoundin the table is almost identical to the compound
in Gomu Haigō-Hō [Rubber Compounding
Methods], published in 1958 24). It can thus beassumed that wartime compounding techniques
hadreachedareasonablelevel.

DM(Benzothiazile disulphide) is a thiazile organic
vulcanisation

accelerator

like

the

Looking at these details, we can say thatthe invention of organic vulcanisation
accelerators that allowed control overvulcanisation was a major breakthroughand revolution in the development of therubber industry. The main points are as
follows.
1. Improved productivity due to reduced
vulcanisation time
2. Less deterioration of the rubber due toshorter exposure time during
vulcanisation
3. Rubber shifted from anexperience-based technology to achemical-theory-based technology
4. Theorisation meant redundancy ofcompounding specialists, who had
previously made their living fromsecret compounds
The above compound is thought to be
30

National Museum of Nature and Science
Vol.16,2011

from the early Showa Period, indicatingthat compounding specialists had
disappeared by the end of the Taisho
Period.
Nevertheless,organic
vulcanisation
accelerators were an American invention;

the major change in rubber technology
following the introduction of thistechnology can be said to exemplify how
the Japanese introduce technology, learn
it and then improve it to make it theirown.

Cited references:
1) Yamada, Hitoshi: “Haigō-Shi [Compounding Specialists]”, Gomu Haigō no Tatekata [Rubber Compounding
Techniques], Vol. 11, Compounding Techniques Research Subcommittee, The Society of Rubber Science andTechnology, Japan, March 2009, p. 80.
2) Kaneko, Hideo: Ōyō Gomu Kakō Gijutsu 12-kō [Applied Rubber Processing Technology, Lecture 12], Taiseisha,
1988.
3) Nihon Gomu Kōgyō-shi [The History of the Japanese Rubber Industry], Vol. 1, The Japan Rubber Manufacturers
Association, ed., 1 November 1969, pp. 42-45.
4) Nihon Gomu Kōgyō-shi [The History of the Japanese Rubber Industry], 1-3, The Japan Rubber Manufacturers
Association, ed., Toyo Keizai, Inc., 1969-1971.
5) Hyōgo Gomu Kōgyō-shi [History of the Hyogo Rubber Industry], Teranishi, Yūzō and Hyogo Rubber
Manufacturers Association, 1978.
6) Gomu Kōgyō no Hatten [Development of the Rubber Industry], Ikeo, Katsumi, Commerce and Industry
Association, 1948.
7) Danroppu Mizumakura 70-nen no Ayumi [The 70-Year History of the Dunlop Water Pillow], Sumitomo Rubber
Industries, 1995.
8) Aoe, Ichirō: Journal of The Society of Rubber Science and Technology, Japan, Vol. 41, pp. 47, 620, 1948; Vol. 42,
p. 1024, 1969, Changing Trends in Rubber Chemicals.
9) Meiji Gomu Hachijū-nen-shi [The Eighty-Year History of Meiji Rubber], Meiji Rubber & Chemical Co., Ltd.
Company History Editing Office, 1980.
10) Nihon Gōseigomu Kabushikigaisha Jūnenshi [The Ten-Year History of the Japan Synthetic Rubber Company],
Japan Synthetic Rubber Company, 1968.
11) 20 Seiki wo Hiraita Gomu Zairyō: Hatten no 100-nen [Rubber Materials Pioneered in the 20th Century: 100
Years of Development], Asai, Harumi, Frontier Publishing, 2004.
12) Sumitomo Gomu Hachijū-nen-shi [The Eighty-Year History of Sumitomo Rubber], Sumitomo Rubber Industries,
1989.
13) The Society of Rubber Science and Technology, Japan Editorial Department: Journal of the Society of Rubber
Science and Technology, Japan, Vol. 69, p. 45, 1996: Visiting Sumitomo Rubber Industries.
14) Gomu Haigō Kokinshū [Collection of Rubber Compounds Old and New], Moriyama, Tokichirō (Mashiba,

31
National Museum of Nature and Science
Vol.16,2011

Tetsuo; Kaneko, Hideo; Katō, Yoshiyuki and Togama Kusakari), Toei, 1940.
15) Nishioka, Masamitsu: Journal of the Society of Rubber Science and Technology, Japan, Vol. 69, p. 34, 1996: The
Story of Mitatsuchi Rubber Manufacturing Company.
16) Ukawa, Keiji: Journal of the Society of Rubber Science and Technology, Japan, Vol. 8, p. 269, 1935: The Rubber
Industry of the Time.
17) Okazaki, Ryūta: Gomu [Rubber], Vol. 1, p. 78, 1929: The Japanese Rubber Industry at the Time of theEstablishment of Mitatsuchi.
18) Tōyō Gomu Kōgyō Gojūnen-shi [The Fifty-Year History of Toyo Tire & Rubber], Toyo Tire & Rubber Company,
ed., 1996.
19) Fujikura Gomu Kōgyō Yomoyamabanashi [Visit to Fujikura Rubber], Fujikura Rubber, ed., 1992.
20) a) Shiraishi Kogyo: Sōritsu 50-shūnen-shi [Fifty-Year Anniversary Publication], Diamond, 1970; b) Personalcommunication with Yoshikazu Shiraki.
21) Tanaka, Sōichirō (trans.): Kōgyō Gomu Kagaku [The Chemistry of Industrial Rubber], Hakubunkan Zōhan, 1912,
p. 205.
22) Heisen Yoko Document.
23) Gomu Jihō [Rubber Times], Vol. 37, No. 11, p. 22, 1958.
24) Mori, Tetsunosuke: Gomu Haigō-hō [Rubber Compounding Methods], Kyoritsu Shuppan, 1958, p. 132.
25) Mori, Tetsunosuke: Gomu Seizō-Hō [Rubber Manufacturing Methods], Japan Chemical Industry Association,
1943.
26) Fukuoka, Harutarō: Gomu Haigō-hō [Rubber Compounding Methods], self-published, 1922, p. 2 (Table 2), p. 43(Table 3).
27) Gomu Gijutsu Nyūmon [Introduction to Rubber Technology], The Society of Rubber Science and Technology,
Japan, Editorial Committee, October 2005.
28) Yamashita, Kōichi: Gomu Seizō Kagaku [The Chemistry of Rubber Manufacturing], Waseda University Press,
1924.
29) Satō, Sadakichi and Morimoto, Kumeitsu: Gomu no Kenkyū [Rubber Research], Koseikaku, 1972.
30) Kawaoka, Yutaka: Karyū Sokushin-zai no Tsukaikata to Riron [Theory and Use of Vulcanisation Accelerators],
Kakosha, 1972, p. 3.
31) Kageyama, Kunio: personal communication, 2008.
32) Hashiguchi, Akitoshi: Journal of the Society of Rubber Science and Technology, Japan, Vol. 70, pp. 514, 657,
1997: One Aspect of the Japanese Rubber Industry in its Infancy and Post-War Rebuilding.
33) Moriyama, Tokichirō: Gomu oyobi Ebonaito Haigō: 1 [Rubber and Ebonite Compounding 1], Koseikaku, 1936,
p. 17.
34) Ōkita, Tadao: Gomu Karyū no Riron to Jissai [Theory and Practice of Rubber Vulcanisation], Reimeisha,August 1951, p. 44.

32
National Museum of Nature and Science
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4. Stage of Growth: Creation of the Domestic Tyre Industry
The Age of Imported Technology from Overseas and Domestically Produced Technology(Taisho-Showa Periods to the End of the War)Japanese tyre companies (Dunlop, Yokohama

marketRubber, Bridgestone, Toyo Rubber) were

establishing a Japanese branch and building thefounded during this period. Following the

Dunlop Rubber Co. (Far East) factory 3).

acquisition of compounding techniques, thisThe factory in Wakinohama was aroundperiod saw the successive creation of domestic

one-third of the size of the grounds of thetyre companies.

headquarters (now Sumitomo Rubber) and

The first half of this period was a time offactory

domestic

overseas

Earthquake, with a two-storied brick building

domestic

occupying a site of around 16,000m2 (5,000

production

manufacturers’oftechnologyorlooking

beforesufficiently

the

Great

promising,

Hanshin-Awaji

production using domestic technology. The

tsubo).

latter half was a time of wartime regime, theestablishment of Dunlop (Far East) (Fig. 4.1;

end of overseas technology imports and thedated 4 October 1909) is shown in the company

development

history Sumitomo Gomu Hachijūnen-shi [Theofindependent

technology.

A

copy

of

the

registrationofUltimately, this period was a time devoted toEighty-Year History of Sumitomo Rubber] 2).

building up technological strength to improve

The arrival of Dunlop with its full-scale

durability

facilities and superior technology was a major(longlife),afundamental

performance for tyres.

stimulus and influence on the Japanese rubber
industry at the time, with its technology still

4.1. The First Half (Time of Imports;hovering in a state of infancy. This built up

1912-c.1930): The Beginning of Japan’s

momentum for the rise of the rubber industry,Tyre Industry

triggered by the First World War. Inspired by
Dunlop, other rubber manufacturing companies

4.1.1. The Beginnings of Dunlop (Far East)

were established one after another from the end

Technologyof the Meiji Period to the start of the Taisho

As mentioned previously, Dunlop (Far East),

Period,the Japanese branch of Dunlop UK, had a lot do
1)

mainly

in

Kobe,

like

satellites

3)

gravitating around Dunlop .

with the start of tyre technology in Japan .

Thus, this period saw Dunlop (Far East) take

In 1909, 20 years after the Dunlop tyre

the lead in rubber technology and rubbercompany was launched in Dublin, Dunlop UK

business, starting the first automobile tyreplanned to expand into the Far East, first

production

establishing a company in Hong Kong, then six

domestically-produced automobile tyre is still

months later, with the outlook for the Japanesepreserved at Sumitomo Rubber 1). See Fig. 4.2.

in

1913.

The

first

33
National Museum of Nature and Science
Vol.16,2011

4.1.2.

Yokohama

Rubber(now

theYokohama Rubber Company) Pre-War
Technology
While Japanese automobile tyres were all still
fabric tyres, the United States was shifting into
an age of cord tyres. This technology first
appeared as the result of an invention in 1908
by American J. F. Palmer. The “cord tyre”
made of blind fabric was developed by
Fig. 4.1. A Copy of the Registration of
Establishment of Dunlop (Far East)2)

Silvertown Cable of the United Kingdom andperfected into a commercial product by US
company Goodrich.

1909

Early pneumatic tyres had a frame ofrubber-coated canvas (fabric), but the threads
would often chafe and break while running due
to the flexure of the tyre, since the canvas had awarp and weft like any other fabric.
Cord tyres (blind-fabric tyres) did not have thehorizontal and vertical threads interwoven but
Fig. 4.2. The First Automobile Tyre Produced
in Japan, 1913, Dunlop (Far East)
Sumitomo

Gomu

5)

Hyakunen-shi

laid in parallel, forming a kind of meshsuperimposed in the direction in which the twolayers of adjoining threads crossed. These tyres

[The
4)

Hundred-Year History of Sumitomo Rubber] ,were successfully commercialised by Goodrichp. 44

in 1910, immediately after Palmer’s invention.
Yokohama

RubberCompany

startedout

Around this time, tyres were very obviously

making fabric tyres but began production ofhand-made in nature. These “fabric tyres” orcord tyres in 1921. This was the beginning of“canvas tyres” were produced by overlapping

cord tyre production in Japan. The invention ofcotton fabric. This method continued until

cord tyres made tyres three times more durable

4)

around 1921 .

than fabric tyres 6) (see Fig. 4.3).

The demand for tyres grew substantially at thistime, accompanied by a growing demand for4.1.3. The Establishment of Bridgestone

durability. A major reform in technology took

(now Bridgestone Corporation)

place in relation to this – a transition from

(1) The details leading up to the establishment

canvas tyres (fabric tyres) to cord tyres.
34
National Museum of Nature and Science
Vol.16,2011

of the company are based on Buridjisuton

production, Ishibashi potentially stood noShijūgonen-shi

chance for success in domestic tyre production.

[The

75-YearHistoryof

Bridgestone].
The

Since Ford Japan and General Motors Japan

distinguishingofwould only use tyres that had passed strict

Bridgestone’s pre-war tyre technology was that

quality testing at their overseas headquarters,

it

the

was

characteristic

domestically

produced

andtechnologically-inferior

Japanese-madeindependently developed and manufactured.

tyres had no chance of being fitted on new

Until that point, other companies were either

automobiles, while the reverence for imported

Japan-based

goods seemingly presented too much of aoverseas

manufacturing

companiesorbranches
wereof

importingbarriertotheircommercial

use

7)

technology developed by overseas partners.

(replacements/repairs) .

In 1928, when Bridgestone’s founder ShōjirōIn April 1929, in absolute secrecy, Bridgestone

Ishibashi was setting up mass production andplaced an order with the Akron Standard Mold

mass production systems for Japanese work

Company in Ohio, USA, via Healing & Co. inshoes and rubber boots, the main player in the

Osaka, for a complete set of equipment neededrubber industry in the West was automobile

to produce 300 tyres in one day 7).

tyres, consuming around 60% of the available“It contained two banner machines (tyrenatural rubber. Thinking that Japan’s futuremoulding equipment), five watch case heaters

would be similar, Ishibashi took the lead and(vertical vulcanisers), two moulds (one for each

decidedtyre size: 29x4.50 and 30x4.50) and othertoproduce

automobile

tyres

7)

domestically .

equipment, as well as materials such as blind

Given that this decision to take on the challenge

fabric cord, breakers and bead wire” 7).

of producing automobile tyres using local
production technology came at a time when
automobile parts such as tyres and evenautomobiles themselves were highly revered
imports and there was no question of domestic

Overlap

Blind weaving

FabricFig. 4.3 Cord Tyre “made by Hamatown Cord in 1921” 6), Blind Weaving (for Cord Tyres) and
Ordinary Fabric
35
National Museum of Nature and Science
Vol.16,2011

Page 32 of Buridjisuton Shijūgonen-shi [TheStarting

75-Yearshows

technology, having a foundation laid on

photographs of the factory facilities (see Fig.

independent research and using cutting-edge

4.4 below); fundamentally, these are little

facilities for the time probably led to successdifferent from modern-day facilities, which

later on.

means that they must have been state-of-the-art

It was a hard struggle leading up to theat the time (there is also a photograph of a

production of the first tyre. The work did not go

Banbury mixer, still commonly used today).

smoothly. One very difficult challenge was

Historyof

Bridgestone]

out

with

domestically-produced

manufacturing the ply cord that formed theskeleton

reinforcing

layer

of

the

tyre.

Vulcanisation was also done completely byhand 7).
Amidst these hardships one on top of another, a
successful tyre prototype was finally produced
Contemporary Banbury mixer

at 4 PM, 9 April 1930. This was the birth of thefirst “Bridgestone tyre” (29 x 4.50 in size,
4-ply). It was a tyre for a small passenger
vehicle. The second tyre was completed on 11
May 7).
Fig. 4.5 shows the commemorative tyres; Fig.

Tyre prototype at the temporary factory

4.6 shows a replica. Domestic production
technology had manufactured its first tyre.

Contemporary 22-inch rollInterior of a tyre factory from this period. Many
women

in

apronswere

employed

Fig. 4.5. Commemorative No. 1 Tyre 7)

inmanufacturing.
Fig. 4.4. Contemporary Factory Facilities 7)
36
National Museum of Nature and Science
Vol.16,2011

Japanese work shoes and rubber boots,
Ishibashi quietly studied rubber, the main raw
material.

He

considered

all

the

specialproperties of rubber and meditated on the futureof rubber itself 10).
According to Risō to Dokusō [Ideals andCreation], Shōjirō Ishibashi had breadth ofvision and a sense of duty; when going about
Fig. 4.6. Replica of the No. 1 Tyre (BShis work, he had insight into technologicalMuseum Collection) 8)

development and took the point of view of acompany existing within society.

The initial idea was crucial to starting businesswith domestic production technology. The

As discussed above, the three main Japanesefounder had a huge impact on this.

companies made different contributions to earlytyre production; tyres were birthed out of the(2) Embodiment of Ishibashi-ism (Risō toearly struggle. As war became imminent, it

Dokusō [Ideals and Creation] by Shōjirō

became harder to import overseas technology;

Ishibashi)in the end it seems that there were no

According to Shōjirō Ishibashi, while mass

significant differences between the three main

production of Japanese work shoes and rubbercompanies in terms of their technology.

boots was already under way around 1928,
what he wanted to make in the future was
9)4.1.4. Contributions Towards the First

automobile tyres , as he felt that tyres were ofDomestically-Produced Tyre

utmost importance.

The three main Japanese companies made theHis perception proved to be very sharp indeed,followingright from the start 9). Despite Japan having

domestically-produced tyre.

contributions

towards

the

first

only a few automobiles at the time, a time
would come when automobiles would be

Dunlop (Far East) (now Sumitomo Rubber

domestically produced; having five to ten

Industries, Ltd.)million cars on the road would mean a

The Japanese factory (in Kobe) ofconsumption of ten to twenty million tyres.

Dunlop UK manufactured the firstAccordingly, making purely Japanese tyres anddomestically-produced tyre in 1913.

selling them at affordable prices would be

Dunlopessential to the development of the automotive

established in 1909.

Rubber

(Far

East)

was

industry.
While

still

continuing

to

mass

produce37

National Museum of Nature and Science
Vol.16,2011

Yokohama Rubber (now Yokohama Rubber

Rubber was established”.

Company)
Imported technology from Goodrich(partner).

Manufactured

the

first

4.1.6.

Establishment

Companies

of

Other

Tyre

12)

domestically-produced cord tyre in

According to the chronological tables in Taiya

1921.

no Hanashi [The Story of the Tyre] (pp.

Yokohama

Rubberwas

232-233), the other manufacturers given below

established in 1917.

entered the tyre business either during wartime

Bridgestone (now Bridgestone Corporation)
Japan’s first tyre produced withor post-war.

domestic technology in 1930 by the

1944: Dai-Nippon Aircraft Tyres(Dai-Nippon

Japan “Tabi” socks Tire Division,

Kōkūki Taiya) (later Ohtsu Tyre & Rubber)

one year before the founding of

established

Bridgestone.

1949: Nitto Tyres(Nittō Taiya) (later Ryoto

Bridgestonewasestablished in 1931.

Tyres(Ryōtō Taiya)) established
1964: Okamoto Riken enters the tyre business4.1.5. Toyo Rubber, Founded in Wartime
Establishment of Toyo Rubber
The following account is from Tōyō Gomu

4.2. The Second Half (Time of Domestic

Kōgyō Gojūnen-shi [The Fifty-Year History of

Production;11)

1930-1945)

Toyo Tire & Rubber].

WartimeTechnology,

Toyo Tire & Rubber Company was establishedunder two parent companies, Toyo Rubber

From the outbreak of war to the end of the war

Industrial and Hirano Rubber Manufacturing.

(technology

Toyo Rubber Industrial was established in May

expansion and control)

1938 by Toyo Boseki for automobile tyre

The times grew dark in the 1930s and the

production as Naigai Saisei Rubber Company

sounds of war could be heard approaching.

(Naigai Saisei Gomu Kabushikigaisya), but

Military colours flew high. As Japan entered achanged its name in October that year. Whilewartime regime, tyre companies set up systems

both companies were built up under Toyofor supplying military goods. There was a

Boseki, they merged and were re-launched as

demand for improved tyre performance in harsh

Toyo Tire & Rubber Company on 1 August

conditions in areas such as durability. With it

1945, right before the end of the war.

eventually becoming increasingly difficult to

From this description, it seems that Toyo

import overseas technology, research began on

Rubber was established in 1943. According todomestic

the chronological tables in Taiya no Hanashi

independent technology began to be developed.

[The Story of the Tyre] 12), “1943: Toyo Tire &Especially after the Pacific War, everything

throughproduction

wartimeproduction

technology

and38
National Museum of Nature and Science
Vol.16,2011

was in military colours; tyre factories were

the facility was complete, with the existing

designated as war factories. Despite initialbuildings having been renovated.

emergency wartime procurements, there was a“The new factory was a four-storey building;shortage of raw materials and production

there was an 84-inch open mill in the basement

became difficult.

where rubber compounding was performed for

Let us examine how tyre companies handledcarbon compounding tread. The basement wassuch circumstances in the area of technology.

segregated to prevent carbon from spreading.
The ground floor was the mill room, for4.2.1.

Dunlop

Japan

(now

Sumitomo

measuring chemicals, peptising and mixing

Rubber)non-black rubber; it was equipped with 84- andDuring this period, the munitions supply of

60- inch mills and other rubber kneading rolls,

Dunlop (Far East), supplied exclusively to theas well as various calenders.

army and navy, was on the brink of crisis and

The first floor was the automobile tyre factory,

certain steps had to be taken to continue

equipped with tread extruders and bead

supplies. In 1933, despite ongoing fierce

moulding machines, as well as tyre moulding

competition in the tyre market, the decline inmachines and vulcanisers.” 13)

yen exchange meant very few automobile tyreThis facility had basically the same layout asimports; Japan entered an age of self-reliancethose of today, other than the compounding

for automobile tyres.

machines using rolls instead of the internal

The entry of Dunlop (Far East) entry into

mixers used today; this indicates that this was aautomobile tyre13)

self-reliance around thisstate-of-the-art facility at the time.

time was as follows.

Dunlop (Far East) changed its name to Dunlop

Politically, 1932 was a dark year and there was

Rubber (Japan) in 1937; on 29 January 1943, it

a sense of uneasiness about the future. Therechanged again to Central Rubber Industries. At

was a sudden rising clamour about rejecting

this point, aircraft production was held as theforeign investment; the munitions supply of

key to victory; increasing efforts were devoted

Dunlop (Far East), supplied exclusively to theto this industry, along with the army and navy.

army and navy, was on the brink of crisis and

The previous year (1942), aircraft production

certain steps had to be taken to continue

had increased to 8,800 machines; in 1943, it

supplies.

doubled to 17,000.

Dunlop (Far East) sought to strengthen its ties

Central Rubber drove the development ofwith the navy as a means of breaking out of thisaircraft tyres, succeeding at this with its own

deadlock.

technology. These were supplied to the army,

It had begun construction on a new factory in

but requests were also fielded from the navy.

1929 to expand its production and sales

The 1944 proceeds from aircraft tyre sales

structure. Three years after construction started,reached¥5.7

million,makingthem the39

National Museum of Nature and Science
Vol.16,2011

second-place flagship product second only toexisting products and gained a very goodbulletproof tanks, even outselling truck and bus

reputation.

tyres

28)

.

Perhapsdue

towartimedemand,other

The 35th anniversary of Dunlop’s founding fellcompanies also made significant improvements

in 1944; under a total war regime, Central

to durability.

Rubber became concealed war plant “Factory
Jinmu 7176” by order of the Munitions
Companies Act

23).

4.2.3. Technology Examples(1) Providing Tyres for Emperor Showa’s Benz

It had achieved the supply of munitions under(Grosser Mercedes)and Domestically-Produced

an all-out regime despite a shortage of raw

Carsmaterials.

The Grosser Mercedes was an ultra-luxury
passenger car made for world leaders and4.2.2. Yokohama Rubber (now Yokohama

multi-millionaires. With an engine capacity of

Rubber Company) 14)

7700cc, 150hp output and top speed of

The Manchurian Incident in September 1931

140km/h, it had an enormous engine and was

led to a rise in demand for military vehicles.

surprisingly high performance for its time. In

The government and military authorities also

1937, Yokohama Rubber was commissioned byconcentrated their efforts on protecting andthe Imperial Household Department at the timedeveloping the domestic automobile industry.

to produce tyres to be fitted to the vehicle;

Increased automobile production meant athese were completed after one and half a year

sudden rise in demand for tyres. From Marchof development. These tyres were specially

1934, Yokohama Rubber set about expanding

designed with cloth-inserted sealant pasted

its primary tyre factory.

inside the tube so that air would not escapeThe most important technical issue waseven if punctured. Their size was 7.50-20 15).

durability. Tyres had to be developed to meet

The durability of the tyres fitted to this highthe increased demand in order to survive theperformancefierceRubber’s

comparable to those of today. This means thattechnical team devoted itself to increasing tyredomestic production technology must have

durability. In April 1937, Yokohama changed

already reached a considerable level at this time.

its trademark on all its tyres and other productsThis is one example of the level attained byfrom “Goodrich” to “Y” for Yokohama andJapanese engineers having to take creative steps

announced its “New Y Tyre” with a Y on theto achieve things on their own, with ittread. This tyre was characterised by abecoming increasingly difficult to importcontinuous Y shaped pattern; with its unique,overseas technology (see Fig. 4.7) 15).

newly-developed tyre cord (patent granted in

At this time, significant progress was also made1939), it was more than twice as durable asoncompetition.

Yokohama

vehiclepassenger

would

vehiclehave

technology

been

and
40

National Museum of Nature and Science
Vol.16,2011

domestically-produced passenger vehicles wereToyota Automobile Museum Collection

also being developed. Fig. 4.8 shows the first(2) Aircraft Tyres

passenger vehicle produced by Toyota (Toyota

Demand for military rubber products steadily

Model AA; replica). The tyres were made byincreased at Yokohama Rubber since theBridgestone.

outbreak of the Second World War against

In light of the circumstances, it must be said

Japan in 1941. Since aircraft tyres in particularthat Japanese engineers had already mastered

had a significant impact on the course of thethe imported overseas technology and attained

war, there was a rush to expand that divisiona high level of domestic production technology,

17)

especially in terms of durability. This was the

Accordingly, in 1943, the Yokohama factory

age of application.

fell completely under the supervision and.

control of the army and navy 18).
In these circumstances, tyres were also
produced for the Zero fighters.
Emperor Showa’s Benz
(1935-1955)
1935 model(7700cc, 150hp, 140km/h)
Benz Museum, donated by
the Imperial Household
AgencyFitted with Yokohama
tyres (made in 1938)

A Zero fighter discovered in Guam in 1963 is
said to have been fitted with Yokohama tyres.
Having gone through 20 years of typhoons, theaircraft was damaged beyond recognition, but
the tyres were still in a useable state 17). This
indicates the high durability capable throughFig. 4.7. His Imperial Majesty’s Car (fromindependently-developed Japanese technology

Yokohama Rubber News) 15)(see Fig. 4.9).

Fig. 4.9. Zero Fighter Tyre 17)
Held
Fig. 4.8. Toyota Model AA, 1936; Toyota’sFirst Passenger Vehicle (Replica)

16)

by

Yokohama

RubberCompany

Hiratsuka Factory(made in May 2006)

550-17 Tyres (Bridgestone)41
National Museum of Nature and Science
Vol.16,2011

4.2.4. Bridgestone 19)(1) Wartime Regime
A directive from the Minister of Commerce andIndustry in January 1939 prohibited the
manufacture of passenger vehicles other thanfor military use; the production of small trucks
was also mostly prohibited. Accordingly,
production of automobile tyres was also limited
to ordinary trucks, most of which were military
vehicles 19).

Tyre for the “Falcon” fighter ‘560 x 190’

Meanwhile, full-scale production and supply of(manufactured in March 1942)

aircraft tyres started in 1939. As the war

Fig. 4.10. Tyre for the “Falcon” Fighter 20)

intensified, production rapidly increased. The

Buridjisuton 75-nen-shi [The 75-Year History

annual production number of around 3,000 inof Bridgestone]

1939 is estimated to have grown around 60
times to 176,000 in 1944.
Bridgestonealso

manufacturingasprogressed

into

wheel

part

its

wartimeofaircraft-related operations. This correspondswith an order from the army in 1942 to supply
combined wheels and tyres for aircraft.
(2) Tyres for the “Falcon” Fighter
While tyres for the Hayabusa “Falcon” fighter
are mentioned in the company history (Fig.

Fig. 4.11. Tyre for the “Falcon” Fighter 8)4.10), an actual tyre for the Falcon is held in theSize: 570-190; made in February 1944 by

Bridgestone Museum (see Fig. 4.11). It is in

Nippon Tire Company

8)

good shape with hardly any deterioration .

Bridgestone Museum Collection
Whilewartimetechnology

wasmunitions-focused, it had come a long way on
its own efforts. On 20 February 1942, thecompany changed its name to Nippon Tire
Company at a request from military authorities
to amend the English name. The Bridgestone42
National Museum of Nature and Science
Vol.16,2011

Tire company name disappeared for ten years,“At the time [around 1941; author note], tyre

until 25 February 1951.

production(3) Level of Aircraft Tyre Technology at the[predecessor organisation; author note] was stillTime

in its infancy. As the war intensified, ensuring

Taiya no Hanashi [The Story of the Tyre], bytyres for the military became top priority andRokurō Hattori, records the following regarding

the company had to respond.

wartime development of aircraft tyres.

Related to this, trucks manufactured by“Looking back, the time before and during the

Kawasaki

war was a time of suffering for JapaneseCompany (now Kawasaki Heavy Industries)

aircraft tyres; many aircraft designers thought

were fitted with tyres by Toyo Rubber

only of flying faster and further – tyres andIndustrial and other companies and given aother things that weren’t used in the air were

five-day road test. The route went out of Kobe

nothing more than a necessary evil. Tyre

from Okayama to Tottori; while it was amanufacturers were requested to produce a tyrerigorousthat could support such and such a weightdemonstrated that Toyo tyres were more

within certain dimensions. … Such poor design

durable than those of other companies. Withand underdeveloped manufacturing technology

theseresulted in frequent serious accidents from tyres

Industrial products were highly rated bybursting.

Kawasaki

However, while it had seemed like every effort

Company; Toyo then received its first order forhad been in vain, light began to dawn on

military truck tyres and tubes.”

improvements in tyre durability. Various

This account indicates that highly durable tyres

elements in tyre design somehow made it

had been developed by Toyo Tire & Rubber as

possible to estimate tyre durability.” 21)

well.

at

Toyo

Rolling

test

foroutstanding
Rolling

Rubber

Stock

the

Manufacturing

time,

results,
Stock

Industrial

the

Toyo

results

RubberManufacturing

This account has some credibility, as these arethewords ofsomeone

at

the

site

of

From the above, it can be considered that there

development (Hattori was a former Bridgestone

was a rising level of interest in tyre durability

engineer, employed in naval aircraft design

as a basic performance factor from around thisduring the war).

time.

By the end of the war, a reasonable level ofdurability had presumably been attained.
4.3. Industry Response to the Wartime
4.2.5. Toyo Tire & Rubber

22)

RegimeAccording to Tōyō Gomu Kōgyō 50-nen-shi[The 50-Year History of Toyo Tire & Rubber]

At this time, there was a form of technicalthe following circumstances occurred.

cooperation in the industry.
43

National Museum of Nature and Science
Vol.16,2011

According to Bridgestone, in January 1938,

Incorporation, Article 1). The Association was

Dunlop Rubber Company (Japan), Yokohama

to carry out various operations in order to

Rubber and Nippon Tire (Bridgestone; author

achieve this aim.

note) anticipated the expected regulation of

These operations can be divided into two broad

rubber distribution in that coming July andcategories: directly and indirectly taking part inestablished the Japan Automobile Tyre Industry

government planning and cooperating with

Association(Nihon

Kōgyō

government policy execution. Above all, theKumiai), gaining government approval in April.

basic mission of the Control Association was to

The Association carried out business incooperate with the execution of government

cooperation

policies.

Jidōsha

with

Taiya

the

Japan

Tyre

Association(Nihon Taiya Kyōkai), but when(i) Taking part in government planningthat Association dissolved in March 1939, the(ii) Cooperating with regulation execution

Japan Automobile Tyre Industry Association

There were seven aspects to cooperating with

inherited all of its operations. 20)

regulation execution: 1. production regulation;

The

Japan

Automobile

Tyre

Association

dissolved

after

operationstoRubberthe

Association(Gomu

Tōsēkai)

Industryceding

2. regulation of supply of raw materials; 3.

itsregulation of product distribution; 4. priceControlregulation; 5. labour regulation; 6. technology

launchedin

January 1943.

regulation;

7.

curtailmentofbusiness

operations.
Of these, the most important task was to do

4.3.1. Wartime Technology

with technology regulation: improving the

By the end of the war, the aforementioned

technology

Control Association was engaging in operations

improving and promoting efficiency in the(1944).

industry in order to increase production during

According to Nihon Gomu Kōgyō-shi [Thewartime.

History of the Japanese Rubber Industry], theThe Rubber Control Association designatedfollowing circumstances were in place.

members, provided mediation and established

The aim of the Rubber Control Association wastechnical

to “provide comprehensive regulation andtechnology division for the purposes ofadministrationtoresearching and improving technology as wellmarketing as well as production and sales ofas exchange and disclosure. It had a productrubberRubbersubcommittee to ensure technology regulation.

Production) in order to provide an advanced

In April 1944, nine articles of regulations onstate defence system and to collaborate in thetechnology exchange and disclosure weredrafting and execution of state policies related

drawn up; these stipulated specific agreements

toregarding technology exchange and disclosure,ofproducts

Rubberoperations(hereinafter

Production”

relatedas(Articles

of

of

the

committees

rubberinindustry

addition

to

and

its

44
National Museum of Nature and Science
Vol.16,2011

as well as an accompanying compensation

Theresystem. Decisions were made to meet thedomestic production of carbon black

demands for increased production

24)

.

were

successive

instancesof(2) Fibres

Accounts such as the following state that

Despite a temporary ease of access toeffective technological advances were made inresources in the south following the onset

the field of rubber.

of the Pacific War, fibres were still in short
supply.

4.3.2.

Specific

Technology

AdvancesinRubber25)

In 1942, a directive was issued to produce

According to Nihon Gomu Kōgyō-shi [Thereinforced rayon and Toyobo and other

History of the Japanese Rubber Industry], ascompanies entered an era of finding practical

the Pacific War intensified, there was aapplications for reinforced rayon. It was foundshortage of raw materials accompanied by athat 20-30% rayon cord was suitable for use in

decline in the quality of rubber products. With

automobile tyres. Yokohama Rubber, Nippon

an increasing demand to ensure rubber products

Tire and Central Rubber each joined forceshigh in both quantity and quality, thewith rayon companies to produce prototypes

technology division of the Rubber Control

and performed running tests on these fitted to

Association planned and implemented an open

trucks and passenger vehicles, reporting very

exchange for superior technology.

good results. In 1943, the technology divisionThis rapidly lifted the overall level ofoftechnology in the rubber industry, making it

Association(Jinken

very significant in the history of rubber

established provisional standards for reinforced

technology. In other words, it would not be

rayon for use in tyre cord. According to a reportexaggerating to say that this rise in the level ofby Automobile Division 3 of the administration

technology provided the basis for the rapid

bureau of the Ministry of Railways, which had

restoration and development of the rubber

carried out practical testing for a year fromindustry in Japan after the war

25)

.

the

newly-establishedTōsēkai)

Rayon

Control

proposedandAugust 1942 to July 1943, “of the 12 tyres, 6
exceeded the life expectancy of the existing

The following is based on research on various

Egyptian cotton cord tyres (24,141km in 1942),

raw materials.

2 by 90% or more, 3 by 80% or more and 1 by

1. Raw materials

68%.” This was a good result, acknowledging(1)Natural rubber; (2) latex; (3) reclaimed

that the average number of kilometres of
25,228 was better than the ordinary product 27).

rubberAs indicated above, it was an age of

2. Secondary materials(1)Domestic

productionof(reinforcing agent)carbonblack

regulations; technology advanced rapidly ascompanies worked together, sharing technology
45

National Museum of Nature and Science
Vol.16,2011

for the sake of development. There are many

This technology is thought to have been applied

accounts regarding the outcome of thisto aircraft such as the “Zero” and the “Falcon”.

technology disclosure. Technology develops

As mentioned previously, the Nippon Tire

when a country has to get by on its own(Bridgestone) tyre on the Falcon fighter and thetechnology.

Yokohama Rubber tyre on the Zero fighter

Taiya no Hanashi [The Story of the Tyre] 26) byshow little outward sign of deterioration,

Rokurō Hattori has the following accountindicating the high level of technology at theregarding cotton tyre cord technology.

time.

“Since spun yarn transmits force by means ofThis is surely the result of incorporating

entwined short fibres, the longer raw cotton

improved product quality through technology

fibres are, the better quality they are. Raw

disclosure.

cotton was graded by an expert who would takea pinch of it between the thumb and index
finger of both hands and tear it several times,

4.4. Summarythen lay the pieces out on black velvet to form akind of fibre length spectrum to judge its

As seen above, the period spanning the Taisho

quality.

Period to the end of the war can be divided two

Later on, to maintain strength, low stretch

ways.

processing was carried out to prevent any

1. The age of Japanese factories for overseas

excess stretching. This was a method oftyre companies or introducing overseas

winding which provided a strong tensile

technology (Dunlop, Yokohama)strength in the winding process; adding water

These

and using fixative would prevent the yarn fromtechnology,

stretching back. This process significantly

themselves and went on to develop their own

improved the quality of cotton cord. During thetechnology.

companiesbutimportedalso

studiedoverseasitforSecond World War, there were concerns about

2. The age of starting independent technology

variation in the lifespan of the company’sfrom the beginning (Bridgestone, Toyo)[Nippon Tire, Bridgestone; author note] aircraft

As the Pacific War era approached, othertyres, but the introduction of Yokohama

countries started to be boycotted and Japanese

Rubber’s

methodcompanies had to get by on their own

through technology disclosure led by the navy

technology. There was little difference between

greatly improved the lifespan of the tyres and

1 and 2 at this point; both rapidly advanced in

reduced the variation. This is a true story I

performance and production technology. The

heard from my immediate supervisor.”

technology evidently reached a very high level

This actually also shows the effects of theduring the war, as they also had to produce alltechnology control associations.

of their own technology despite an extreme

lowstretchproduction

46
National Museum of Nature and Science
Vol.16,2011

shortage of raw materials and expand theiradaptive abilities to produce goods for the
military, with rigorous usage conditions. The
level of durability would have increased rapidly
during this period.

Cited references:1) Sumitomo Gomu Hachijū-nen-shi [The Eighty-Year History of Sumitomo Rubber], Sumitomo Rubber Industries,
Ltd., October 1989, p. 31.
2) Sumitomo Gomu Hachijū-nen-shi [The Eighty-Year History of Sumitomo Rubber], Sumitomo Rubber Industries,
Ltd., October 1989, p. 18.
3) Sumitomo Gomu Hyakunen-shi [Hundred-Year History of Sumitomo Rubber], Sumitomo Rubber Industries, Ltd.,
October 1989, p. 39, on which the following is cited. Nihon Gomu Kōgyō-shi [The History of the Japanese Rubber
Industry], Vol. 1, The Japan Rubber Manufacturers Association, ed., 1 November 1969, pp. 203-204.
4) Sumitomo Gomu Hyakunen-shi [Hundred-year History of Sumitomo Rubber], Sumitomo Rubber Industries, Ltd.,
December 2009, p. 44.
5) Sumitomo Gomu Hyakunen-shi [Hundred-year History of Sumitomo Rubber], Sumitomo Rubber Industries, Ltd.,
December 2009, see preface.
6) Yokohama Gomu Sōritsu 50-Shūnen [Yokohama Rubber 50-Year Jubilee], Yokohama Rubber Company, October
1967, p. 22. A description of this cord tyre also appears in Sumitomo Gomu Hachijū-nen-shi [The Eighty-Year
History of Sumitomo Rubber], p. 33.
7) Buridjisuton Nanajūgo-nen-shi [The 75-Year History of Bridgestone], Bridgestone Corporation, May 2008, pp.
31-33.
8) Bridgestone Today Museum Collection, 3-1-1 Ogawa Higashimachi, Kodaira-shi, Tokyo
9) Ishibashi, Shōjirō: Risō to Dokusō [Ideals and Creation], Diamond, December 1969, p. 27.
10) Ishibashi, Shōjirō: Risō to Dokusō [Ideals and Creation], Diamond, December 1969, p. 152.
11) Tōyō Gomu Kōgyō 50-nen-shi [The 50-Year History of Toyo Tire & Rubber], Toyo Tire & Rubber Company, 21
March 1996, p. 65.
12) Hattori, Rokurō: Taiya no Hanashi [The Story of the Tyre], Taiseisha, June 1992, pp. 232-233.
13) Sumitomo Gomu Hachijū-nen-shi [The Eighty-Year History of Sumitomo Rubber], Sumitomo Rubber Industries,
Ltd., October 1989, p. 89.
14)Yokohama Gomu Sōritsu 50-Shūnen [Yokohama Rubber 50-Year Jubilee], Yokohama Rubber Company, October
1967, p. 27.
15) “His Imperial Majesty’s Car”, Yokohama Rubber News, No. 34, October 1972, p. 10.
16) Toyota Automobile Museum Collection, 41-100 Yokomichi, Nagakute, Aichi. Originally released as “Toyoda”
with the voiced sound indicators included on the final character in the Japanese script. Changed to “Toyota”

47
National Museum of Nature and Science
Vol.16,2011

without the voiced sound indicators in October 1936. (Discussion with Toyota Automobile Museum.)17)Yokohama Gomu Sōritsu 50-Shūnen [Yokohama Rubber 50-Year Jubilee], Yokohama Rubber Company, October
1967, p. 31.
18) 80 Shūnen Kinen We Tokubetsu-gō [80-Year Anniversary We Special Edition], Yokohama Rubber Company,
October 1997, p. 53.
19) Buridjisuton Nanajūgo-nen-shi [The 75-Year History of Bridgestone], Bridgestone Corporation, May 2008, pp.
55-56.
20) Buridjisuton Nanajūgo-nen-shi [The 75-Year History of Bridgestone], Bridgestone Corporation, May 2008, p. 57.
21) Hattori, Rokurō: Taiya no Hanashi [The Story of the Tyre], Taiseisha, June 1992, p. 23.
22) Tōyō Gomu Kōgyō 50-nen-shi [The 50-Year History of Toyo Tire & Rubber], Toyo Tire & Rubber Company, 21
March 1996, p. 70.
23) Sumitomo Gomu Hachijū-nen-shi [The Eighty-Year History of Sumitomo Rubber], Sumitomo Rubber Industries,
Ltd., October 1989, pp. 123-124.
24) Nihon Gomu Kōgyō-shi [The History of the Japanese Rubber Industry], Vol. 1, The Japan Rubber Manufacturers
Association, ed., 1 November 1969, pp. 317-320.
25) Nihon Gomu Kōgyō-shi [The History of the Japanese Rubber Industry], Vol. 1, The Japan Rubber Manufacturers
Association, ed., 1 November 1969, p. 328.
26) Hattori, Rokurō: Taiya no Hanashi [The Story of the Tyre], Taiseisha, June 1992, pp. 108-109.
27) Nihon Gomu Kōgyō-shi [The History of the Japanese Rubber Industry], Vol. 1, The Japan Rubber Manufacturers
Association, ed., 1 November 1969, p. 332.
28) Sumitomo Gomu Hachijū-nen-shi [The Eighty-Year History of Sumitomo Rubber], Sumitomo Rubber Industries,
Ltd., October 1989, pp. 121-122.

48
National Museum of Nature and Science
Vol.16,2011

5. Stage of Maturity: The Age of Motorisation
5.1. Stage 1: Technology in the Posr-War

motorisation (see Fig. 5.1) 2); later, as society

Rebuilding Period

suddenly became motorised, major changes
happened with tyres as well. The distinguishing

5.1.1. The Age of New Materials – the Rise

characteristic of this period was the appearanceof the Post-War Motorisation Ageof new materials.

(1) Post-War Situation
The recovery from the chaotic post-war
aftermath 1) (the age of new materials) was asfollows.
Although the rubber industry had taken a major
hit from war damage, its recovery wascomparatively quick, given the state of otherpost-war industries. Reasons for this included
the fact that the industry had had training incollective control and had taken to collective
1928 1950 1970

behaviour before and during the war, the fact

1990

2005

that raw rubber and fibres that had been held by

Fig. 5.1. Ownership of Four-Wheeled Vehicles

the army and navy during the war were releasedin Japan (unit: 10,000 vehicles) 2)

into the private sector at the end of the war in(Sekai Jidōsha Tōkei [World Motor Vehicle

greater amounts than had been expected during

Statistics], Vol. 6, 2007)

the war, and the fact that military demand could
be converted to private demand relatively(2) The Appearance of New Materials

simply; but the main reason was a prompt andFor the Japanese tyre industry, this period was

relevant directive to all rubber factories in thea time of importing and learning overseas

country from the Rubber Control Association

technology once the country reopened after thebased on government policy at the end ofwar.

August 1945, outlining “matters on provisional

The greatest change was the introduction of

measures on handling the new situation in the

new materials. This included the transition in1)

rubber industry” .

reinforcing material from cotton to synthetic

To put it simply, this directive put anfibres such as rayon and nylon and theimmediate end to the exclusive production of

emergence of synthetic rubber as a raw

military goods and allowed private sector

polymer. Consequently, difficulty arose in thisproduction to continue or increase.

period in adopting new materials without

This period was the entry point into the age ofchanging bias processing machines. There are
49

National Museum of Nature and Science
Vol.16,2011

tales of hard times learning to use nylon andthat bombed Kyushu towards the end of the war

SBR. In other words, this period was a time ofcontained nylon, something previously not seenchanges in raw materials.

in Japan. These were ideal for aircraft tyres in
terms

of

impactresistanceandfatigue(3) Reinforcing material (tyre cord)

resistance and accordingly were already in use(i) Changes in tyre cordduring the war 5).

In modern terms, tyres are made of fibre
implemented because tyres are pressure vessels.
Tyres are a kind of balloon; natural rubber on
its own cannot counteract the internal pressureand needs to be wrapped in a strong,non-stretch material. It needs reinforcing fibre
to do that. With internal pressure in the tyre,

Usage volume (1,000t)

reinforced rubber (FRR). This structure was
Nylon
Rayon

tension is applied to the tyre cord. Actual tyres(Year)

are wrapped in reinforcing materials such as

Fig. 5.2. Post-War Changes in Tyre Cord 10)

fibre and steel cords. The tension applied to thereinforcing layer is determined by the balance(ii) Details on tyre cord 4)

between internal pressure and external shape.

1) Cotton cord

Consequently, the tension applied to the cord

Until regenerated and synthetic fibres appeared,

on a turning tyre fluctuates. Therefore, tyre

cotton was the only fibre with the adequate

cord must be rated not only on strength andperformance, cost, availability, and otherbreaking

elongation,

perspective

of

but

fatigue,

from

the

factors to be used as an industrial fibre. Most

deteriorationandtyre cord was also cotton. Since cotton has

also

adhesion between the rubber and the cord.

short fibres, it has to go through a spinning

Rayon started to be used in the United Statesprocess that pulls and twists the fibres together.

from around the 1940s; nylon appeared in the2) Rayon cord

1950s and gradually grew in popularity, while

Fibre made by chemically extracting andcheaper polyester also began to be used. Rayonre-forming natural fibres (cellulose). The tyre

cord was replaced by nylon in post-war Japan.

cord is made using the viscose method, in

Looking at the volume of consumption, as

which a pulp of wood or other material isshown in Fig. 5.2, we see that nylon took overtreated with caustic soda, dissolved in carbon

as the main cord fibre in the mid-1960s.

disulphide and aged to form a sticky liquid

Nylon’s replacement of rayon in the United

called viscose, which is pushed through aStates is thought to be around 10 years earlier.

nozzle to form threads. Increasingly higher

This means that the tyres on the B-29 bombers

quality tyre cords emerged, while and rayon
50

National Museum of Nature and Science
Vol.16,2011

and reinforced rayon have even recently beennylon was often used as reinforcement for this

rated as having no noise, vibration or flat spots

layer, thereby winning back a major field of use(a phenomenon in which the part of a tyre infor it to date. This layer heats up while thecontact with the road changes shape after thevehicle is in operation and forms another layer

car has stopped and cooled) when production

over the steel belt due to thermal contraction,

conditions are good and have been used in highthereby improving high speed durability. Nylon

performance tyres. Following the appearance ofclearly exemplifies the rise and fall of aradial tyres, it continued to be used in thematerial in a very short time.

carcasses of high performance tyres, mainly inEurope. In Japan, there has not been much(4) Organic fibre tyre cord adhesion

success with stable fibres, made by cutting spun(i) RFL adhesive

thread into short fibres and twisting them.

RFL is a fibre adhesive made up of a3) Nylon cord

combination of resorcinol (R), formaldehyde

Synthetic nylon tyre cord appeared on the(F) and latex (L). In the 1940s, Church andmarket in Japan around 1950. This was madeManny et al. discovered that a liquid adhesiveby melt spinning a dissolved liquid. As it wasmade by adding resorcinol formaldehyde resin

highly stretchy in that state, it had to undergo ato an aqueous solution of rubber latex had

stretching operation to align the crystals andsuperior adhesion properties. For the next half

make it stronger; the stretch also had to be

century, RFL has been the main adhesive usedwithin an appropriate range.

on fibres such as rayon, nylon, polyester,

Most tyres at the time were for trucks and buses,

aramid and glass fibre.

but nylon matched that need. Nylon is still used

The adhesion mechanism is thought to be as

today in bias tyres for heavy services such as

shown in Fig. 5.3. The figure shows nylon ontrucks, buses, construction machinery andthe left, rubber on the right and resorcinol andaircraft. Nylon is stronger than rayon and does

formaldehyde simply in between, causing a

not lose its strength when wet like rayon does.

three-dimensional resinification reaction. The

However, nylon shrinks in the heat and requires

main

a process of cooling while still inflated after

fundamentally forming a secondary bondvulcanisation.

(hydrogen bond) rather than a primary bond

Later, reinforcing layers for passenger vehicle(chemical bond) with the nylon and the rubber.

tyres were made of combinations of steel cord

As shown in the figure, a resinification reaction

andchange, nylon

occurs in the resorcinol between the rubber andappeared to have lost its main function;

the nylon, producing a resin between the rubber

however, an increasing number of tyres had

and nylon. The adhesive is produced along withanother layer of reinforcing material in thethe resinification reaction between the rubber

circumferential direction above the belt andand the nylon.

polyester.

With

that

cause

of

adhesion

is

the

resin

51
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RFL resin is a significant invention that can be

Yokohama Rubber Company developed aused generically on most fibres. It also made arayon tyre in 1950. By 1955, it hadvery significant contribution to the tyredomestically produced an aircraft tyre withindustry.

nylon cord in it 13).
RFL resin(adhesive layer)

Nylon layer

Toyo Rubber switched to rayon in the same
Rubber layer

period. According to its company history,
various tyre manufacturers had started using

Hydrogenbondrayon cord by 1951, while Toyo itself
Cross-linking
pointcompleted a dipping machine, put separation
countermeasures in place and put rayon tyreson the market in February 1952 12).
Research on nylon tyres was carried out inearnest from the spring of 1954; from
December 1958, they were marketed all over

Hydrogenbond

the country for trucks and buses 12).
As outlined above, major changes in cord
happened at around the same time.
Cross-linking
point

Fig. 5.3. RFL Adhesion Mechanism between
Nylon and Rubber

8)(6) Composition of Rubber Compounds
The rubber used in tyres is a compound ofvarious compounding agents. In other words, itis basically a compound of natural rubber,(5) Changes in Cord by Companies

styrene-butadiene

According to the history of Bridgestone,

synthetic rubber (raw rubber) with reinforcingchanges in cord happened as follows. By theagents such as carbon black added to it, as well

1950s, the United States was mostly using

as compounding agents such as vulcanizing

rayon instead of cotton; Bridgestone also

agents (to cause a cross-linking reaction torecommended a change to rayon due to its low

produce elastic rubber) and anti-ageing agentscost. This change took place rapidly, as by(for durability) mixed in. By changing the ratio

1952, rayon was being used in 80% of theirof the raw rubber, reinforcing agents andtyres.

vulcanizing agents, these compounds can form

Later, there was a change to nylon cord

the required rubber; in other words, various(initially for aircraft tyres); this change also

kinds of rubber from hard to soft can behappened quickly, with sales commencing in

produced for use in various components. The

1959. Major changes were happening with cord

greater the capacity, the greater the impact on

at this time 18).

the properties of the rubber; natural rubber

rubber

(SBR)

or

other

52
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(polymer) has the greatest impact.

capital.

(i) Adoption of synthetic rubber (natural

Goodyear in the United States and a factorypolymers)

started operating in Yokkaichi in 1960,

Right before the Second World War, theproducing 45,000 tons of SBR per year 11) 16).

Japanese government noted the importance ofMeanwhile,

synthetic rubber as a military resource. In 1938,

technology from Goodrich Chemical in theit set up a 10-year plan to establish a synthetic

United States and started operating a factory inrubber industry; in 1941, it issued the Organic

Kawasaki in 1959, producing 8,500 tons per

Synthesis Businesses Act(Yūki Gōsē Jigyō Hō)year of mainly special non-SBR rubber, such as

to protect and develop it 16).

NBR and high styrene rubber. Production of

Research on the industrialisation of butadiene

SBR

rubber in Japan grew more prolific as the war

expanding to a total of 30,000 tons, including

started. Through its occupation of southern

10,000 tons of SBR and 20,000 tons of NBR

territories, Japan was able to secure sources ofand other special rubber. In 1965, a second

natural rubber, which meant that SBR was noplant opened in Tokuyama, producing a total of

longerthe

45,000 tons per year, including 20,000 tons of

production of oil resistant NBR (acrylonitrile

SBR and 15,000 tons of BR. It supplied its own

butadiene rubber) 16).

raw

As

the

necessary.

war

Focus

ended,

shiftedtheAlliedtoForcesTechnology

startedbutadiene

was“Nipponindistillation methods.”

Zeon

1962,

using

imported

its

with

own

from

imported

production

extractive

16)

Headquarters prohibited the production of

The change from natural rubber to SBR

synthetic rubber, providing a minor setback.

involved a struggle with reduced tack. In the

However, from around 1950, the Ministry of

moulding process during manufacture, tyres are

International Trade and Industry, The Japan

moulded from layers of unvulcanised rubber,

Rubber Manufacturers Association and thewhich requires tack (stickiness). Since SBR is

private sector began discussing the need toless tacky than natural rubber, it was moredomestically produce synthetic rubber once

difficult to mould. The invention of tackifiers in

more. Later, as the plans for the petrochemical

the United States solved this issue and paved

industry began to take shape in Japan, a plan

the way for later widespread use 17).

was proposed around 1955 requiring synthetic

Changes were taking place in compounding

rubber for B-B fraction in oil-cracked gas

technology, with large amounts of fillers andrather than from alcohol. In 1957, the Act onoils being compounded as well as SBR.

SpecialRubberWhen Japan Synthetic Rubber Company was

Production Businesses(Gōsē Gomu Seizō Jigyō

established, the majority of the members of theTokubetsu Sochi Hō) was issued and Japan

Bridgestone Research Division Tokyo OfficeSynthetic Rubber established through ¥1 billion

transferred there and successfully producedof government funding and ¥2.5 billion in

SBR. Meanwhile, the “Bridgestone catalyst”

MeasuresforSynthetic

53
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was perfected for cis polybutadiene rubber and

The post-war raw rubber situation is shown inpatented in 1959; this catalyst provided a

Fig. 5.4. It is clear how rapid the changes insuccessful cis polybutadiene compound. In

raw materials were during this period. From

1963 a pilot plant started operation; the mainaround 1960 in particular, there was a rapid

factory was completed in 1964 and started

increase

operating in 1965. This was Japan’s first cis

produced synthetic rubber used.

polybutadiene and was rated very highly; theLooking at the above post-war initiatives intechnology was exported many times 15).

synthetic rubber, the two things that later

One account on the introduction of synthetic

undergirded Japan’s tyre industry were the factrubber tyres states that “the Passenger Vehicle

that some knowledge and experience inTyre Division perfected the country’s firstcompounding existed before the war and thesynthetic rubber tyre, throwing new light onto

fact that even though Japan imported American

the devotion to natural rubber and greatly

technology after the war, it had the ability to

improving the durability of truck and bus tyres

develop its own technology in a coordinatedby using reinforced rayon.”13)

New product

in

the

volumeofdomesticallyfashion.

development, which had seemed to stall for aPre-war compounding research is thought towhile in the turbulent times following the war,

have aided the progress of post-war polymer

gradually revived from around the time thatcompounding technology. In other words, pastrubber regulation ended (1950).

experience made a significant contribution.

Yokohama Rubber Company announced aThis was one type of technology import insynthetic rubber tyre in 1957

14).

modern Japan.
As shown in the figure above, the demand forrubber grew rapidly with the rapid spread of
Synthetic
rubber(domestic
production)

Natural rubber

motorisation up until around 1970. There was a
rapid

increaseindomestically

producedsynthetic rubber from around 1960 in particular.
Around half of this synthetic rubber was used

Synthetic rubber(imported)in tyres.
(ii) Carbon Black
Carbon black was produced by a US company
in the 1870s. Later, the channel process ofFig. 5.4. Transitions in Raw Rubber Volumes

making it from natural gas was devised and(Domestic

became the main method used. During the

Production)(1953-1968) Japan3)

in

Post-War(MT = metric ton)

Second World War, the furnace process
emerged along with synthetic rubber; the oil
54

National Museum of Nature and Science
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furnace method used today, using heavy liquid

Basic properties ofcarbon blackoil instead of natural gas, became the main
method used.
Carbon black is a type of soot found in the(A) Layer surface(steel surface)early 20th century to have a reinforcing effecton rubber. It became an essential reinforcing(B) Crystallite

agent because it rapidly improves the strengthof the rubber when added as such.
With the appearance of synthetic rubber,
furnace black became the carbon black used
due to its high reinforcing properties.

(C) Particle
size

While carbon black is a stratified substancecomposed of carbon, it is particulate in form;

Structure

the surface of the particles react with the

Carbon black structure (provided by Mitsubishi

polymers, causing a reinforcing effect (see Fig.

Chemical Corporation)
Fig. 5.5. Form of Carbon Black 6)5.5). The larger the size of the particles, thesmaller the surface area and the lesser thereinforcing effect. However, the smaller theProperties of Carbon Blackparticles, the greater the surface area and theParticle Size

Large

Small

greater the reinforcing effect. During thisBreaking

Low

High

period, carbon particles were made smaller instrength

size to increase the reinforcing effect.

Hardness

Low

High

Wear resistance

Low

High

Heat

Low

High

build-up(lower is better)
As an overall trend, small-particle carbon black
is used on tread, the area of the tyre in contact
with the road, where wear resistance isimportant. Large-particle carbon black is used
Electron micrograph of carbon black (provided

in the rubber covering the internal cord in orderby Mitsubishi Chemical Corporation)

to reduce the heat build-up.
Fig. 5.6 shows how tyre production volumes
have increased. As seen in this figure,production increased by 50 times in a 30 year
period from 1955. The figure shows a rapid
55

National Museum of Nature and Science
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post-war increase. This period was a time ofJapan and was adopted in passenger vehicles

rapid increase in production and challenges infrom the 1970s onwards; by the 1990s, almost

keeping up with and mastering rapid changes inall vehicles had tubeless tyres. Only a few

raw materials.

tube-type tyres remain for trucks and buses.
While this technology involving fixing an innerAmount of rubber used intyre production (1,000 tons)

Number of vehicles
produced (1,000 cars)

liner of low-air-permeable rubber onto theinternal surface of the tyre was a key
technology,

thedecisive

blow

was

the

emergence of halogenated butyl rubber. Butyl
rubberNumber of vehicles
producedwasalready

known

as

a

low-air-permeable rubber and was used in

Amount of rubber used intyre production

tubes.
However, butyl rubber could not be fixed
directly onto the inner liner of the tyre, as it
does not co-vulcanise with other rubbers.
Halogenated butyl rubber, developed in the(Year)

United States in 1960, made it possible toFig. 5.6. Transitions in Japanese Vehicle

co-vulcanize

Production Numbers and Amount of in Tyre

accordingly made it possible to attach it

Production (Amount of Rubber Used) 9)

directly to the inner liner area of the tyre. It is

it

with

other

rubbersandstill in use today. Brominated butyl is the usual(7) Development of Tubeless Tyres

type of halogenated butyl rubber used today.

Tubeless tyres were developed by US company
Goodrich in 1947; these have an inner liner of
low-air-permeable rubber on the internalsurface of the tyre, which plays the part of thetube, as shown in Fig. 5.7. Besides having

Inner liner
Tubefewer components and attaching to anddetaching from the rim more easily, tubelesstyres also serve to improve safety at higha) Ordinary tyreb) Tubeless tyre

speeds, since the air does not all escape at once

Fig. 5.7. Comparison of the Structure of

if the tyre incurs a small puncture, such as

Passenger Vehicle Tyres 7)

would be incurred by running over a nail.
Further, there is no need to separately
manufactureatroublesome

tube.

This

epoch-breaking technology advanced rapidly to56
National Museum of Nature and Science
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Cited references:
1) Yokohama Gomu 40-nen-shi [The 40-Year History of Yokohama Rubber], Yokohama Rubber Co., Ltd., January
1959, p. 398.
2) Buridjisuton Nanajūgo-nen-shi [The 75-Year History of Bridgestone], Bridgestone Corporation, May 2008, p. 30.
(Source) Sekai Jidōsha Tōkei [World Motor Vehicle Statistics], Vol. 6, 2007
3) Data from Gomu Gijutsu Gaidobukku [Rubber Technology Guidebook], Nikkan Kogyo Shimbun, Ltd., October
1973, p. 26.
4) Hattori, Rokurō: Taiya no Hanashi [The Story of the Tyre], Taiseisha, June 1992, pp. 106-112.
5) Hattori, Rokurō: Taiya no Hanashi [The Story of the Tyre], Taiseisha, June 1992, p. 24.
6)Gomu Gijutsu Nyūmon [Introduction to Rubber Technology], The Society of Rubber Science and Technology,
Japan, ed., October 2005, Maruzen, p. 52.
7) Hirata, Yasushi: Journal of the Society of Rubber Science and Technology, Japan, Vol. 68, 25, 1995.
8) Matsui, Junichi; Toki,Masamichi; Shimizu,Hisao: Journal of the Adhesion Society of Japan, Vol. 8, No. 1, p. 26,
1972.
D. I. James et al.: Trans. Proc. Inst. Rubber Ind., Vol.39, No. 3, p. 103, 1963.
Written based on these documents.
9) Material from Japan Automobile Tyre Manufacturers Association (from Nihon no Taiya Sangyō 2007 [Japan’s
Tyre Industry 2007]).
10) Figure based on Gomu Kōgyō Binran [Rubber Industry Handbook], fourth edition, The Society of Rubber
Science and Technology, Japan, ed., January 1994, p. 549.
11) Buridjisuton Nanajūgo-nen-shi [The 75-Year History of Bridgestone], Bridgestone Corporation, May 2008, p.
105.
12) Tōyō Gomu Kōgyō 50-nen-shi [The 50-Year History of Toyo Tire & Rubber], Toyo Tire & Rubber Company,
March 1996, rayon p. 99, nylon p. 117.
13) Sōritsu 50-Shūnen Yokohama Gomu [50-Year Jubilee of Yokohama Rubber], Yokohama Rubber Company,
October 1967, p. 38.
14) 80 Shūnen Kinen We Tokubetsu-gō [80-Year Anniversary We Special Edition], Yokohama Rubber Company,
October 1997, p. 55.
15) Buridjisuton Nanajūgo-nen-shi [The 75-Year History of Bridgestone], Bridgestone Corporation, May 2008, p.
106.
16) Data from Gomu Gijutsu Gaidobukku [Rubber Technology Guidebook], Nikkan Kogyo Shimbun, Ltd., October
1973, pp. 22-23.
17) Gomu Kōgyō Binran [Rubber Industry Handbook], fourth edition, The Society of Rubber Science andTechnology, Japan, ed., January 1994, p. 467.
18) Buridjisuton Nanajūgo-nen-shi [The 75-Year History of Bridgestone], Bridgestone Corporation, May 2008, pp.
83-87.

57
National Museum of Nature and Science
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5.2. Stage 2: From Bias Tyres to Radial

Breaker
Carcass

Tyres

Belt

Belt
Carcass

Carcass

5.2.1. Change in Structure: The History of
Changes in Production Technology
Following the post-war high economic growtha) Bias tyreb) Radial tyrec) Belted bias

period from the 1970s onwards, there was atyre

rapid transition in Japan from bias tyres toFig. 5.8. A Comparison of Bias, Radial andradial tyres. This is thought to be the greatest

Belted Bias Tyre Structures 1)change in tyre technology both before and after
the war. As well as changes in tyre structure,

Fig. 5.9 shows the transition in the proportion

steel cord also appeared as a reinforcingof radial tyres produced in comparison to othermaterial,intyres in Japan. The reason radial tyres became

manufacturing methods and facilities andpopular so suddenly was that the expansion ofequipment.

highway

meaningThis

all-out
broughtchanges

improved

networks

andimprovedcarperformance and revolutionary changes in all

performance demanded better tyre performance

directions.

and radial tyres met the needs of users in terms

Steel radial tyres with steel cord reinforcementof stability and controllability (cornering power,

were developed by Michelin in France. Aetc.) at high speeds, as well as better durability,

passenger vehicle tyre was announced in 1948,

betterfollowed by a truck/bus tyre in 1953. These areconsumption at high speeds.

the most widely used tyres today.

The drawback to radial tyres was that theywear

resistance

and

lower

fuel

offered poor riding comfort on bad roads;(1) Changes in Tyre Structure

however, this was not a major problem in JapanThe following figure shows the difference

as the rapid expansion of highway networks at

between bias tyres and radial tyres. Bias tyre

the time (see Fig. 5.12) meant road conditions

carcass ply overlaps with the direction of thewere improving.

cords running in alternate directions on a bias,

As seen in Fig. 5.9, radial tyres were used inhence it is called a bias structure. Radial tyrepassenger vehicles in the 1990s and for mostcarcass ply has the cords running radially fromtruck and bus tyres in the 2000s.

the centre to the outside when viewed from theside, hence it is called a radial structure. Belted
bias tyres are somewhere between the two (seeFig. 5.8).

58
National Museum of Nature and Science
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Proportion of radial tyres (%)

about in the United States as a result of the

Passenger
vehicle tyres

issue

of

havingtomakechangestomanufacturing facilities and equipment. Textile

Truck tyres

radial tyres were actively produced in Japan
Light truck tyres

and other countries where road conditions wereless than ideal.

(Year)

There were repeated discussions at the time in

Fig. 5.9. Proportion of Radial Tyre Production

the United States whether to continue on within Japan2)

the existing belted bias tyres or to transition toradial tyres like Europe. The reality was that
belted bias tyres had taken a firm hold and thethan in France and other countries in Europe,demand for them was continuing to grow 12).

but earlier than in the United States (see Fig.

Later, radial tyres gained a firm position in the5.10).

United States as well.

Proportion of radial tyres (%)

Radial tyres gained popularity in Japan later

The period of transition from bias to radial
tyres saw temporary structures such as belted
France
UK

Spain
West
Germany

bias tyres in the United States and textile radial
tyres in Europe and Japan, but in the endJapaneveryone settled on steel radial tyres.

USIn terms of facilities and equipment, Japan had
entered a time of high economic growth and(Year)

various tyre companies were building new

Fig. 5.10. Proportion of Radial Tyres forfactories anyway, so they established these as

Passenger

radial tyre factories. Motorisation was already

VehiclesMaintenance)(Salesfor

Vehicle3)

fully fledged in the United States and so thetransition

from

bias

to

radialandthe

The transition from bias to steel radial tyres

accompanying major facilities and equipment

was not a sudden change; there was a transitionchanges were somewhat delayed, so belted bias

period in which two structures emerged: belted

tyres were a proposed compromise.

bias tyres and textile radial tyres.

The greatest differences between radial tyres,

Belted bias tyres could be manufactured on

bias tyres and belted bias tyres are the number

existing facilities and equipment and thusof layers of ply and breakers (belts) and the

avoided the issue of having to make changes toangle of the cord (see the figure below);manufacturing facilities and equipment. Textile

however, there were various different cordradial tyres offered the same poor ride comfort

materials and bead structures 21).

as steel radial tyres. Belted bias tyres came59
National Museum of Nature and Science
Vol.16,2011

Ply angle (˚)

Belt

angle

Distances in Japan 11)(˚)
Radial ply tyre

70-90

10-60

(2) Manufacturing Methods

Bias ply tyre

30-40

30-40

Radial tyre factories required major changes toBelted bias ply

30-40

20-30

bias tyre factory facilities and equipment. Let
us now discuss factory facilities and equipment.

tyre

Manufacturing

Belt angle

Belt
Carcass

Facilities

andEquipment(Radial Tyre Factory)
Fig. 5.13 shows manufacturing facilities andequipment 4). Broadly speaking, tyre production
involves the following five processes.
(i) Compounding (Mixing and kneading theraw rubber and various kinds of compounding
agents in a mixer. Fig.5.14 shows a mixer.)

Top of tyre(ii) Extruding (Extruding the kneaded rubberfrom an extruder in a predetermined size andPly angle

shape.)
Fig. 5.11. Tyre Ply/Belt Structure(iii) Rolling (Topping the rubber with fibre,

As previously mentioned, radial tyres had

steel cord and other reinforcing materials.)

issues with ride comfort, but this was solved by(iv) Moulding (Doubling together the materials

the development of highways.

prepared in (ii) and (iii) and forming a tyre

Radial tyres were also more suited to travellingshape.)

at high speed than bias tyres. From these two(v) Vulcanising (Making it into a finishedfactors, the development of highways can beproduct by adding heat.)said to line up with the change to radial tyres

The facilities and equipment for this have

(Fig. 5.12).

remained basically unchanged since the 1970s.

(Year)
Fig. 5.12. Transitions in Highway Extension
60
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Mixing processa Mixing process
Compounding
agentsNatural Synthetic
rubber rubber

Kneading the rubber andforming strips (warming mill)Rubber for cords(Roll)

Rolling process

Rubbercutting

Mixing(mixer)Rubber for(Dipping)
Rubber for
beads
Dipped in chemicals
tread
Carcass

b-1 Material processing
Carcass, belt

Calender (rubber
overlaid on cord)
Belt

Cord weaved intoa belt shape

Cuttingc Moulding processb-2 Material processing
Bead

Bead wiresalignedWrapped in rubber
and extruded (beadextruder)Moulding
process

Wrapped in rings(bead moulding
machine)Extrusion
Tyre mould
Carcass, belt,
beads and tread
assembled
together into atyre shapeb-2 Material processing
Tread

Extruding tyre tread rubber(tread extruder)
Cooling (cooling tank)

Vulcanizing process

d Vulcanising/finishingprocess
Heat and pressure
applied to increaserubber elasticity. Patternapplied to tyre surface.

Green tyrecompleted

Completion

Finishing /inspecting

Fig. 5.13. Tyre Production Process 4)61
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Vol.16,2011

Weight
cylinderInput 1
WeightInput 2
Back door

Hopper door
Rotor

Casing

Latch
Exhaust Drop door

Rotor
Rubber is moved rotates
and kneaded
within the left andright chambers

Rubber is mixed withthe compounding
agents between therotor and the casing

Fig. 5.14. Mixer (Banbury Mixer) 5) and Model of the Interior of a Mixer(3) Details on the Tyre Manufacturing

Areas with a predetermined cross-section such

Processas the tread (the area that comes into contact(i) Mixing (Kneading)with the surface of the road) are achieved by an

The process of making un-vulcanised rubber by

extruding process. After being kneaded in the

combining the various compounding agentsmixer, the tread rubber is plasticised with aweighed according to a recipe. This is a very

warming mill and then fed into an extruder,important task that affects the properties of thewhere it is extruded through a nozzle in a

final product.

pre-setFig. 5.14 shows a Banbury mixer.

predetermined

These are internal mixers. The material goes

extrusion area is then cooled and the tread

into a central area called a mixing chamber. A

rubber is cut to the required lengths and stored.

rotor with two blades side by side rotates within(iii) Calender Process (see Fig. 5.16)

the chamber to create a shearing force between

The calender process produces breakers, belts

the opening and the chamber wall. The raw

and other materials by coating fibres and wire

rubber, carbon black and other fillers placedcords with a thin layer of rubber on both sides

into the input are rubbed together and blended.

(topping). For steel cord, a creel containing the

The blades on the rotor are designed to mix thenecessary number of steel cords to fit the width

tread

shape,

therebycross-sectional

forming
shape.

aThe

5)materials evenly .

of the calender is set in a stand. The wire cords(ii) Extruding Process (see Fig. 5.15)

are unwound from each creel, collected
62

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together and aligned at intervals like a comb. A
sheet of rolled rubber is then pasted on top ofcord calender processing has become anthem. For fibre, the fibre cords are lined up

essential manufacturing process in the age ofwith a coarse weft and put in the calender. Steelradial tyres.

Warming mill

Extruder

Cooling

Cutting
Tread sidewall

Fig. 5.15. Extruding Process 14)

Pre-heated drum

Unwinding

FestoonSpliceZ calender#1 Dancer roll#1 Pull roll

Cooling drum
Festoon#2 Dancer
roll

Wrapping

Steel cord calender
β ray thickness gauge

Creel stand4-roll calender Cooling

FestoonWinderFibre calenderFig. 5.16. Calender Process 15)

63
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(iv) Moulding Processthat the pre-vulcanisation shape of bias tyres isThis process differs the most between bias andquite different from the shape of the finishedradial tyres. Fig. 5.17 below shows the

product

difference in moulding methods between bias

pre-vulcanisation shape of radial tyres is quite

6)

and radial tyres .

after

vulcanisation,

while

the

similar to the shape of the finished product after
vulcanisation.

Sheet

Fibre reinforcing
material(v) Vulcanisation Process
Cylindrical shapeformed by winding
the moulding drum
Beads implantedThis process also differs significantly between
bias and radial tyres, because the shape of thetyres is quite different prior to vulcanisation.
Tyres that have finished the moulding process(un-vulcanised tyres) are called green tyres.

Ply wrapped

These tyres are pressed into a tyre mould byinternal pressure and then vulcanised. At this

Carcass inflated
once side tread
attached
Cap tread and belt
attached

Tread attachedpoint, the tread pattern, side design andstamped characters on the surface of the mould
are imprinted on the tyre. At the same time, thetyre is heated inside and out through a medium
such as steam, water or gas and the entire tyre

Green radial
tyre

Green bias tyreis undergoes a vulcanisation reaction, turning it
into elastic, vulcanised rubber and the tyre iscompleted. Heating is done internally andexternally. There are two methods of external
heating: using a jacket-type hot plate or

Fig. 5.17. Tyre Moulding Process 6)

shutting the mould in a pressure vessel andpumping in steam around it. Internal heating is

Tyre

production

involvesanumberofachieved by inserting an airtight pouchcomponents being overlaid, shaped into a tyre,(vulcanisation bladder or air pack) injected with

put into a mould and heated (vulcanised) tosteam, water or gas. Since tyres do not haveform the final product. While the transition to

uniform thickness, heat is not supplied evenly

radial tyres meant changes had to be made in

to all areas, making it difficult to achieve a

all processes, the greatest change was in theuniform degree of vulcanisation. It is importanttyre moulding process. The pre-vulcanisation

to complete vulcanisation in such a way to(pre-heating) state differs for radial and bias

avoid

tyres (see Fig. 5.17). From the figure, we see

deterioration of the rubber. The Bag-O-Matic

excessive

heating

andconsequent64
National Museum of Nature and Science
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Vertical spring constant(BOM) press (Fig. 5.18) is a popular vulcaniser
currently in use.

Lateral spring
constant
6.45-13 Bias tyre
Lateral load (kg)165SR13 Radialtyre

Vertical deflection (mm)Fore-and-aft spring constant
6.45-13 Bias tyre

165SR13 Radialtyre
Lateral deflection (kg)Torsional spring constantTorsional torque(kg-m)

Fore-and-aft load (kg)

Load (kg)6.45-13 Bias tyre

165SR13 Radialtyre

Fore-and-aft deflection (mm)165SR13 Radial tyre
6.45-13 Bias tyre
Torsion angle (˚)

Torque Q, torsion angle α

Fig. 5.19. How to Measure Various Static
SpringFig. 5.18. BOM Vulcaniser (When Open) 20)(4) Bias and Radial Tyre Performance

Constants

andSampleLoad-Displacement Curves 18)
1) Vertical Spring Constant (Z direction)

Comparison

The vertical spring constant is the slope of(i) Spring Constant 18)

the curve between the vertical load on the

The spring characteristic of tyre function is thetyre and the vertical deflection. This spring

property that allows the tyre to change shape

constant mainly relates to tyre vibration andwhile resisting external forces acting on it andride comfort (frequency range of aroundthen return to its original shape once the force

30Hz or less). The lower the vertical springis removed. This is usually denoted as a “spring

constant, the better the ride comfort.

constant”, comprising the ratio between the2) Lateral Spring Constant (Y direction)

external force and the direction of the change in

The lateral spring constant is the slope ofshape. The following are four static spring

the curve between the pulling force and theconstants (see Fig. 5.19).

lateral displacement where a vertical load isapplied to the tyre and it is pulled laterally
on the road surface. This spring constantrelates to the cornering properties of thetyre.
3) Fore-and-Aft Spring Constant (X direction)
The fore-and-aft spring constant is the slopeof the curve between the pulling force andthe fore-and-aft displacement where avertical load is applied to the tyre and it is65

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pulled forwards on the road surface. This

low rolling resistance (good fuel consumption).

spring constant relates to the oscillation of

As shown in Fig. 5.20, rolling resistancethe tyre in the fore-and-aft direction.

relative to speed is higher in bias tyres and the4) Torsional Spring Constant (Z rotation)difference increases with speed. As shown in

The torsional spring constant is the slope of

Fig. 5.21, radial tyres have lower rollingthe curve between the torque and theresistance compared to bias tyres even relative

torsional angle where a vertical load is

to load.

applied to the tyre and the contact area ofcentre of the contact area as the centre ofrotation. This spring constant is an indicatorof tyre torsional stiffness. This property ishigher in radial tyres than in bias tyres. The
increased stiffness demonstrates the effectof the change to radial tyres in the age of

Rolling resistance (kgf)

the tyre rotates on the road surface with theBias tyre: 6.45-13 4PR
Radial tyre: 165R13 (steel)
Rim: 41/2Jx13
Pneumatic pressure: 1.7kgf/cm2
Load: 385kgf
Bias tyrehighway travelling.

Radial tyre

The radial tyre structure has less rigid sidewalls

Fig. 5.20. Rolling Resistance of Radial andand more rigid belts, meaning less flexibility inBias Tyres 7)

Speed (km/h)

the tread area due to the load and a direction of
the vertical spring constant is measured withthe tyres inflated, radial tyres have a lower
vertical spring constant, but they offer poor ride
comfort over bumps because of the highrigidity of the belts.

Rolling resistance (kgf)deflection causing overall eccentricity. Since
Bias tyre:
6.45-13 4PR

Radial tyre:
165R13 (steel)
Pneumatic pressure:
1.7kgf/cm2(ii) Rolling ResistanceLoad (kgf)

When comparing the performance of radial andbias tyres, there is a clear difference in loss due

Fig. 5.21. Load and Rolling Resistance 7)

to deformation because of the degree of
deformation from stress. The difference in the

While radial tyres had better fuel consumption,

degree of deformation of the overall tyre isasexpressed as a difference in rolling resistanceinexpensive in the United States at the time,(related to fuel consumption). Since radial tyres

and the change to radial tyres progressed more

have a little amount of deformation, they have aslowly there than in Europe.

shown

above,

fuel(gasoline)was66
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(iii) Cornering

vehicle is called the cornering force and causes

Two aspects of tyre performance relate to

the vehicle to move in a curve. The force that

manoeuvrability: braking and controllability

rightens this is called self-aligning torque.

(cornering). Let us discuss cornering.
Consider a skidding tyre.

Tyre cross-section A, C

When the steering wheel is turned to the rightwhile the vehicle is in motion, as shown in Fig.
5.22, the operation of the steering wheel puts
the rotational plane of the wheels at an angle tothe direction of travel of the car. Because the

Tyre cross-section B

Horizontal deflection in the tyredue to force in the horizontal
direction

Traction area

Wheel surface

Slip area

Centre of tyre tread
Direction of motion

car tries to keep going straight ahead due toβ: Slip angle

inertia, a disconnection occurs between therotational plane of the tyres and the direction of
travel

of

the

car.

The

angle

disconnection is called the slip angleof
16)

Fig. 5.23. Tyre Slipping Sideways 16)

this

.

(v) Difference in Manoeuvrability
When a vehicle is cornering around a bend, acornering force is generated to oppose thecentrifugal force on the tyres (see Fig. 5.24).
The cornering force increases in a linear
fashion as the slip angle increases, reaching its
maximum value when the slip angle reaches or

(a)

(b)

The

(c) Turning

exceeds a certain value. The structural element

Travelling

momenttheα: Slip angle

with the greatest effect on the cornering force isstraight

steering wheelof the front

the flexural rigidity of the tread area. Radial

is turned

wheelstyres have a belt layer with high flexural

α: Slip angle

β: Slip angle

rigidity in the tread area, which means that theyof the front

ofoffer far greater cornering force than bias tyres.

wheelswheelstherear

The slope of the straight-line portion of theFig. 5.22. Relationship Between the Direction

cornering force is called cornering power and isof Travel of the Car and the Direction ofoften used as a property value to indicate

16)

cornering performance. One reason for the

Rotation of the Tyres

changetoradial

tyres

was

their

(iv) Cornering Force and Self-Aligning Torquemanoeuvrability. As shown in Fig. 5.25, radial

When slipping sideways, the tyres themselves

tyres have greater cornering power than bias

contort against the surface of the road (see Fig.

tyres. This means that radial tyres are easier to5.23). The sideways force exerted on thedrive on and better to manoeuvre.
67

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The tread area (the area in contact with theCornering force CF

surface of the road) also has the highest

Loadcontribution factor to rolling resistance. When
this area is in contact with the surface of theroad, radial tyres fluctuate less and so requireless work. This also means that the area incontact with the surface of the road fluctuates
less, meaning that radial tyres are also better interms of wear resistance.
(vi) Tyre Functions
As mentioned in the introduction, tyres have

Slip angle

the following four functions.

Fig. 5.24. Cornering Force 17)- Bearing a load (support)- Acting as a spring (absorption)- Conveying driving and braking forces

Cornering power

Tyres: 165SR13 steel radial
165SR13 textile radial
6.45-13 4PR bias
Internal pressure: 1.7kg/cm2
Steel radial
Textile radial(transmission)- Facilitating steering of the vehicle(turning)
These are vital functions in which the tyres aspart of the vehicle serve as an intermediary inestablishing a mutual relationship between thevehicle and the surface of the road. However, itBias

was not until the transition to radial tyres thatthese functions started to be clearly manifested
in tyre development, thanks to easier turningand transmission with increased rigidity andLoadother radial tyre characteristics. This also

Fig. 5.25. Cornering Power and Tyre

coincided with the advent of the age of highStructure8)

speed travel.

As given above, the appearance of steel radial

5.2.2. Change of Materials

tyres dramatically improved automobile turning

The transition from bias to radial tyres meant aperformancechange in materials as well.

andhigh-speed

straight-line

stability. This is a major factor enabling today’s(Polyester, steel cord)safe highway travel for everyone.
68
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made of hard rubber, while the sidewall
between these areas is made of soft rubber. The
Natural rubber
Synthetic rubber
Reinforcing material
Steel
TextileBead wire
Compounding agents

raw materials consist of rubber and reinforcing(tyre cord). As shown in Fig. 5.26, the rubber
portion, including rubber, reinforcing agents
such as carbon black, and compounding agents,
accounts for at least 80% of the tyre.

Rubber/filler/chemicals 80%(2) Rubber for Each Component
Example of
WeightMain
Composition
Composition
Ratio (%)
Type
Naturalrubber,Rubber50.5
synthetic
rubberReinforcing
Carbon black
25.5
agent
SilicaSteel cord
Tyre cord
13.4
Textile cord
Vulcaniser,
vulcanisation
accelerator,
Compounding vulcanisation
10.6
agent,
agentsanti-ageing
agent, filler,
softener
Source: Japan Automobile Tire Manufacturers
Basic
Composition

Association
http://www.jatma.or.jp/index.html
Fig. 5.26. Radial Tyre Composition andMaterials Used in Each Part
(1) Radial Tyre Materials
As previously mentioned, tyres are generallycomposed of more than 10 components (see Fig.
1.3 in Chapter 1). Each component has its
respective function; suitable materials are
selected, combined and systematised to fulfil
those functions. Generally, the area that comesin contact with the surface of the road and thebead area that comes in contact with the rim are(i) Tread and Sidewall
Tread rubber (the part that comes in contact
with the surface of the road) plays the role oftransferring the forces applied to the tyre to thesurface of the road. Of all the rubber used in thetyre, tread rubber has to withstand the mostexternal mechanical force to protect the tyre
from

the

road

surface

so

that

the

pressure-vessel carcass is not damaged. In
terms of rubber properties, it has to havesuperior strength, tearing force and wear
resistance. Accordingly, it is usually a selectionof natural rubber, SBR or BR polymers blended
withfine-grained,

high-reinforcing

carbonblack. However, while fine-grained carbon
black is highly reinforcing, it generates a lot ofheat when restraining polymer movement. Thisis a major issue because it is a fuel-inefficient
behaviour.
Naturalrubber

has

a

high

balanceofperformance; in particular, it is lower in heatgeneration than synthetic rubber and is still
often used today in tyres with higher heatgeneration during operation, such as truck andbus tyres, construction machinery tyres andaircraft tyres.
An increasing amount of SBR was being used69

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for passenger vehicle tyres, but the SBR itself

more detail in Chapter 6.1.

was difficult to process. Use of oil-extended
SBR

(oil

includedduringpolymer(iv) Bead Area Rubber

manufacture) became adopted as standard. This

Since the bead area contains a steel wire tomethod was effective for compounds with oil

connect the rim and the rubber tyre, the coatedadded to improve processability. Oil-extended

surface of the cord and the rubber must adhere

SBR was patented in 1950 by US company

together. Since this area also has to stay firm,

General Tire and was later used throughout thenatural rubber is often used with a lot of carbon

world.

black, with consideration given to heat build-up

SBR was the ideal technology for tyre tread forand adhesion.

passenger vehicles, but it took second place tonatural rubber for truck tyres, bus tyres and(v) Tubeless Tyre Inner Linerother heavy duty vehicle tyres.

Solved by using halogenated butyl to maintain

Sidewalls do not come into contact with thestable tyre pressure (discussed in Chapter 5.1).

ground, but they are subjected to repeatedbending and so must be fatigue resistant. They

(3) Reinforcing Material

are usually made of NR/BR polymer and soft

The change from bias to radial was not a simple

carbon and are also often combined withchange in structure; it was also combined with

anti-ageing agents because they are exposed toa change in materials in a very short space ofsunlight. To perform their necessary function,

time.

sidewalls must be flexible, fatigue-resistant,reinforcing material: belts were switched toage-resistant and ozone-resistant.

steel and carcasses were switched to polyester

This

was

particularly

evident

in(for passenger vehicles). For truck and bus(ii) Carcass Rubber

tyres, both belts and carcasses were eventually

Carcass rubber must adhere well to cord, haveswitched to steel.

low heat build-up and be able to withstandPassenger vehicle tyres also had a further layer

shear stress. Natural rubber is the main rubberof fibre reinforcing (cover material) over theused because of its superior adhesive properties

belt. Nylon was often used for this and in someand heat generation.

cases aramid fibre was also used. Fig. 5.27
shows the relationship between tensile strength(iii) Belt Rubberand stretch for various fibres.

Belt rubber is the rubber that covers thereinforcing steel cord; natural rubber is mainly
used for this. This rubber must be adhesive tothe steel cord and also age-resistant. This
adhesion and age-resistance are discussed in
70
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The drawback with polyester cord is that it has

Tensile strength (N)a greater decrease in strength due to twisting
Steelthan nylon or rayon and is less adhesive to

Aramidrubber than nylon or rayon. Before RFL
adhesive, now commonly used, it required
two-step processing, needing a primer-likeVinylonPolyesterRayon

pre-treatment.
Consequently, it is used in passenger vehicle
66 nylontyre carcasses but not on truck and bus tyres
and other tyres with greater shear stress

Rubberbetween the ply. Since the fibre itself issusceptible to heat build-up, the rubber material

Stretch (%)
Fig. 5.27. Tensile Properties of Various Cords

is susceptible to deterioration; furthermore, thepolyester itself can lose strength when the ester
bonds hydrolyse.

As shown above, the change from bias to radial
was a significant change, encompassing a(ii) Aramid Cordchange in structure as well as a change inAramid cord was announced as a dream fibre

materials.

with twice the strength per weight as nylon andaround eight times the elastic modulus. An(i) Development of Polyester Cord Carcasses

aromatic polyamide in structure, it has thefor Passenger Vehicle Tyres

drawbacks of being expensive, weakening with

Polyester is somewhere between nylon andrepeated compression strain (fibrillisation) andrayon in nature; it performs better against

beingvarious drawbacks of nylon cord, especially inConsequently, it has not been used as a main

the areas of flat spots (a temporary flat area on

reinforcing material.

difficulttoadheretorubber.

a tyre against the road having cooled down
after travelling), dimensional stability and(iii) Steel Cord

manoeuvrability in smaller tyres such as

Steel cord wire is high-carbon steel (0.7%)

passenger vehicle tyres. In other words, inmade into thin strands using a die. This process

terms of firmness, it has more rayon-likehardens it, so it is heat-treated, tempered andproperties. Since it is also cheaper than rayon inthen coated with brass plating to provide a

price, it could be said in some ways to havelubricating effect on the die to make it possible

spelled the end of rayon. However, high quality

to draw it. Heat is applied in the vulcanization

rayon is still used in top quality tyres where

process during tyre production; a reaction

high manoeuvrability is required.

between the rubber and the coating during this71

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process causes the cord and rubber to adhere

the single-layered twist structure has 2-5

together. In other words, the brass plating notfilaments twisted together; this is often used for

only acts as an adhesive between the steel cordpassenger vehicle tyres. The two-layered twist

and the rubber, but also acts as a lubricant tostructure has a 2-3 filament cord in the centre

prevent friction between the cord and the diewith 6-9 filaments twisted around it; this isduring cord production. The final stage ofmainly used in truck and bus tyres. The

drawing is carried out and the strands are

three-layered twist structure comprises thecomplete. The strands range in thickness fromtwo-layered twist structure with a further 14-15

0.15mm to around 0.38mm. These strands are

filaments twisted around it; this is often used

twisted together to form the cord. While thefor larger tyres, from truck and bus tyres tosteel cord used varies between tyres, the moreconstruction machinery tyres

complex the structure, the more is involved in
the twisting process and the greater the cost. In

Single twist

other words, steel cord with thinner strands andmoretwistshasbetterflexuralfatigue

resistance, but since this makes the processing

Two-layered twist

more complicated and increases the price, cordwith a simpler structure is usually used instead.
The plating process, drawing, twisting andThree-layered twist

other technologies are essential to development
and much research and development went into
these while radial tyres were being developed.

Fig. 5.28. Basic Steel Cord Structures forJapanese steel cord is top-level throughout the

Passenger Vehicles, Trucks and Buses 9)

world; it has been highly regarded as having
fewer impurities in the steel wire, meaning
fewer breaks during the drawing process, as

As shown in Fig. 5.29, the structure of steel

well as other performance factors.

cord used in tyres increases in size from thatused in passenger vehicle tyres and that used in(4) Cord / Rubber Combination

truck and bus tyres. Tyres with heavier loads,(i) Example Steel Cord Structures

such as truck and bus tyres, have a thicker

The structures (twist structures) of steel cord

structure. Construction vehicle tyres use an

for truck and bus tyres are as shown in Fig.

even stronger cord. These steel cords are used

5.28 (single-layered twist, two-layered twist

for different purposes according to the size ofand three-layered twist). There are also

the tyre and the site of use.

structures for larger tyres that have multiple
layers of twists. As seen from these structures,
72
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Cross-SectionofSteel Cord for a
Passenger Vehicle

Cross-Section of SteelCord for Trucks and
Buses

1×2

3+6

1×4

3+9+1

2+2

12CC + 1

2+7+

3 + 9 +

passenger vehicles changed to steel radial tyres,1

15 + 1polyester started being used in carcasses inFig. 5.31 shows the changes in the amount oftyre cord used in the United States. By contrast,
the decline in rayon use and start of nylon use
took place about ten years later in Japan.
Polyester usage also started later in Japan thanin the United States. As there is little difference
between the two countries in terms of whensteel cord came into use, it is fair to say that as

Fig. 5.29. Example Structures of Steel Cord forJapan 19).

Tyres (Cross-Section) 9)(5) Post-War Tyre Cord Trends and theRayon

Change to Radial Tyres
Fig. 5.30 shows the changes in tyre cord usage

CottonNylonfrom the 1960s in the post-war era to the year

Polyester
Steel
Glass fibre

2000. As can be seen from these results, there

Aramidwere major changes within a short space oftime: rayon had been replaced by nylon by the
1960s, while the transition to steel cord andFig. 5.31. Changes in Tyre Cord Usage in thepolyester accompanied the shift to radial tyres

United States 19)

from the 1970s onwards.
Thus, the transition to radial tyres was
Consumption by Weight (kt)accompanied by major changes in cord along
within a short space of time.
Steel
Nylon

Polyester

Rayon(Year)

Tyre Cord Consumption by Type

Fig. 5.30. Tyre Cord Consumption by Type 10)

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Cited references:
1) Hattori, Rokurō: Taiya no Hanashi [The Story of the Tyre], Taiseisha, June 1992, p. 6.
2) Watanabe, Tetsuo: Taiya no O-Hanashi [The Story of the Tyre], Japan Standards Association, October 2002, p. 35.
Rewritten to include the latest data from documentation published by the Japan Automobile Tire Manufacturers
Association.
3) Rewritten to combine Watanabe, Tetsuo: Taiya no O-Hanashi [The Story of the Tyre], Japan Standards
Association, October 2002, p. 36, Fig. 1.19 (b) and Hirata, Yasushi: Taiya no Hensen ni tsuite [Changes in Tyres],
Journal of The Society of Rubber Science and Technology, Japan, Vol. 68, 1995, p. 25, Fig. 7.
4) Gomu Gijutsu Nyūmon [Introduction to Rubber Technology], The Society of Rubber Science and Technology,
Japan, ed., Maruzen, October 2005, p. 8.
5) Gomu Kōgyō Binran [Rubber Industry Handbook], fourth edition, The Society of Rubber Science and Technology,
Japan, ed., January 1994, p. 1073.
6) Gomu Kōgyō Binran [Rubber Industry Handbook], fourth edition, The Society of Rubber Science and Technology,
Japan, ed., January 1994, p. 747.
7) Gomu Kōgyō Binran [Rubber Industry Handbook], fourth edition, The Society of Rubber Science and Technology,
Japan, ed., January 1994, p. 750.
Rewritten from Ueno, Kazumi: Jidōsha Gijutsu [Automotive Technology], Vol. 34, No. 10, 1960.
8) Jidōsha-yō Taiya no Kenkyū [Studies on Automobile Tyres], Yokohama Rubber Company, ed., April 1995, p. 138.
Jidōsha Kōgaku Zensho [Compendium of Automotive Engineering], Vol. 12, Tyres and Brakes, Sankaido.
9) Cross-section structures only taken from Gomu Kōgyō Binran [Rubber Industry Handbook], fourth edition, The
Society of Rubber Science and Technology, Japan, ed., January 1994, pp. 557-558, Fig. 2.5 and Table 2.1.
10) Watanabe, Tetsuo: Taiya no O-Hanashi [The Story of the Tyre], Japan Standards Association, October 2002, p.
83. Rewritten by combining this figure with the two figures in Gomu Kōgyō Binran [Rubber Industry Handbook],
fourth edition, The Society of Rubber Science and Technology, Japan, ed., January 1994, p. 549.
11) Drawn up from the Ministry of Land, Infrastructure, Transport and Tourism Road Statistics Yearbook. (SeeBuridjisuton Nanajūgo-nen-shi [The 75-Year History of Bridgestone], p. 221.)
12) Sumitomo Gomu Hyakunen-shi [Hundred-year History of Sumitomo Rubber], Sumitomo Rubber Industries, Ltd.,
December 2009, p. 176.
13) Watanabe, Tetsuo: Taiya no O-Hanashi [The Story of the Tyre], Japan Standards Association, October 2002, p.
81.
14) Hattori, Rokurō: Taiya no Hanashi [The Story of the Tyre], Taiseisha, June 1992, p. 126.
15) Hattori, Rokurō: Taiya no Hanashi [The Story of the Tyre], Taiseisha, June 1992, p. 124.
16) Hattori, Rokurō: Taiya no Hanashi [The Story of the Tyre], Taiseisha, June 1992, pp. 58-59.
17) Jidōsha-yō Taiya no Kenkyū [Studies on Automobile Tyres], Yokohama Rubber Company, ed., April 1995, p.
130.
18) Jidōsha-yō Taiya no Kenkyū [Studies on Automobile Tyres], Yokohama Rubber Company, ed., April 1995, pp.

74
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29-30.
19) Hattori, Rokurō: Taiya no Hanashi [The Story of the Tyre], Taiseisha, June 1992, p. 106.
20) Gomu Kōgyō Binran [Rubber Industry Handbook], fourth edition, The Society of Rubber Science andTechnology, Japan, ed., January 1994, p. 1118.
21) Gomu Kōgyō Binran [Rubber Industry Handbook], fourth edition, The Society of Rubber Science andTechnology, Japan, ed., January 1994, p. 739.

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6. The Coming of Age of Radial Tyres
6.1. The Age of Durability: The Coming of(static) and strain from rolling on the roadAge of Radial Tyres in the Age of Durability

surface while supporting a load (dynamic).
(i) Static Strain

Even for radial tyres, the basic area of

Strain generated by tension from internal

performance is durability. Tyres must fulfilpressure differs between radial and bias tyre

their lifespan. Accordingly, with the transition

structure. In the radial tyre structure commonly

to the radial tyre structure, durability was theused today, the carcass cord follows a radial

first thing that had to be achieved. The early

path along the surface of the tyre and has aradial tyre era in particular was a time of

fairly uniform level of strain at any given point,

significant durability issues, such as thewhile the strain is reduced slightly in the crownadhesion between the steel and the rubber, but

area due to the hoop effect of the belt. Alongthese were overcome as time progressed.

the belt cord, the strain is greatest at the centreof the crown, while a free end is formed at the6.1.1. Tyre Breakdown

shoulder area with zero strain. By contrast, theTwo things cause tyres to lose the strength theyshear strain to counter planar deformation is

had when new: mechanical strain and generated

greatest at the ends of the cords. Shear strain atheat. The extent of this varies according to how

the edges of the radial tyre belt is related tothe tyre is used, from uneven terrain andseparation faults (faults in which the rubber

unpaved roads causing major impact andsplits and layers peel away) in this area. Belt

deflection to highway-like conditions enablingedges in truck and bus tyres running withhigh speeds on unobstructed roads with few

particularly heavy loads are also a factor forbends, stops or starts. Tyres will break down if

breakdowns under this same strain (see Figs.

they encounter any abnormality that pushes

6.1 and 6.2).

Care must be taken so that the rubber fromwhich tyres are composed does not reach that
limit while running. Consequently, it isShear strain

beyond the limits of their remaining strength.

necessary to make it harder for the rubber tolose its strength. This requires a structure thatprevents heat build-up both structurally andSteel belt

locally.
(1) An Examination of Strain 1)

Fig. 6.1. Shear Strain on Radial Tyre Belt 1)

There are two types of tyre strain: strain(greater at the edges of the belt)

generated by tension from internal pressure76
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between the rubber and the cord.
Not under load
While the vertical and horizontal external
Under load
forces acting on the tyre, namely, driving,braking and cornering forces, all incur strain,
Flexure (against R)

Flexure (with R)

the lateral forces are particularly impacting. Fig.
6.3 represents this situation. The belt of a radial
tyre is subjected to in-plane flexure from lateralforces; it is subject to stretching strain

Fig. 6.2. Change in Tyre Shape When Under

externally and subject to compressive strain

Load 1)internally. The edge of the radial tyre belt is
faced with very harsh conditions, being(ii) Dynamic Strain 1)

subjected to overlapping strain from internal

When a tyre is made to roll under load, theinflation pressure, strain under load and strain

formerly solid torus shape is pressed against afrom lateral forces.

plane at the part in contact with the ground.

As seen from Fig. 6.3, compressive strain andViewed from either the cross-section or the

stretching strain occur directly below the load,

circumference of the tyre, the curvature of theparticularly when the belt is subjected to lateraltyre wall changes shape and flexural strain

deformation. This means that cracks are likely

occurs. In other words, it changes from theto occur when steel cord is present in the rubber

shape it had with only internal pressure appliedat the edge, such as in the belt.

to it. According to the cross-sectional diagram

The belt edges in radial tyres are exposed toin Fig. 6.2, the side area is subjected to flexureharsh conditions, being subject to overlappingin a direction that reduces the curvature R ofstrain from internal inflation pressure, strain

the flexure, but in other areas (the crown,

under load and strain from lateral forces (seebuttress and bead areas), the tyre is bent in a

Fig. 6.4). In other words, easing the strain on

direction that increase the existing curvature R.

the ends of radial tyre belts to prevent

In the circumferential direction, the start andseparation is an important durability factor.

end of the area in contact with the ground areWith the transition to radial tyres, it haspressed by the surface of the road and a change

become a vital issue to prevent separation at thein shape occurs, reducing R. This kind ofends of highly structured reinforcing materials

flexural strain causes intensive strain on thesuch as steel cord.

ends of the belt and the folded edges of thebead, in the same way that the cord and rubber
are of course subjected to stretching andcompressive strain. Micro strains also occur,
affecting the adhesion of the boundary layer
77
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Tyre circumference

Belt width

Kicking out

Depression
Directly
below load

Carcass edge line on theStretching strain from horizontal deformation stretched side
Carcass centre line (neutral
Compressive strain fromposition)
Carcass edge line on thevertical deformation
compressed side
Rim centre line

particularly at the edges of the belt, as
mentioned above, due to differences in stiffness(by four digits on Young’s modulus) between
steel cord and the rubber used in the belt
covering the steel cord (see Table 6.1).
Durability

Horizontal Shape of a Radial Tyre Belt and thephenomenon; breakdowns often start fromAccompanying Stretching and Compressive

microscopic defects, expanding from that point1)

and developing into major breakdowns. Belt

Strain under load

Air inflation strain

Shear strain on belt edge (%)

Strain on the Belt Edge

Strain while
cornering

Fig. 6.3. Projected Diagram of the Change in

is

based

on

the

breakdownedges in particular are free ends and so aresusceptible to cracking (edge separation).
Stretchedside of belt

Lateral force

Compressedside of belt
Load

Withstanding breakdown around the steel cord
is required as a basic performance factor.
Table 6.1. Comparison of Various Substances
on Young’s Modulus of Elasticity 17)Comparison of Various Substances on Young’s
Modulus of Elasticity

Air pressure

Unit N/m2 (Newtons per square metre)(multiplied by 10-7 to give approximate

Fig. 6.4. Shear Strain on Belt Edge Generated

kgf/mm2)

While Cornering 1)

Substance

Ex1010

Iron

20-22

6.1.2. Durability During the Transition to

Copper13

Radial Tyres

Aluminium

7

In terms of the factors that affected tyre

Lead

1.6

durability in the time of transition to radial

Wood (oak)1.3

tyres, the major changes were the switch in

Glass

7-8

structure from bias to radial and the use of steel

Polystyrene

0.38

cord as a belt material. (Of course, fibre textile

Nylon 66

0.36

cords were also produced for a while, but steel

Polyethylene

0.076

radial tyres gradually became the norm.)

Elastic rubber(1.5-5.0)x10-4

The use of steel cord in the belt area of radial
tyres led to a susceptibility to breakdown due to

Durability using steel cord depended on the

stress concentration in the boundary layer

durability of the rubber coating to withstandbetween the rubber and the steel cord,

stress concentration and the adhesion between
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the steel cord and the rubber.

decreased is an important factor in its durability.

Accordingly, let us discuss the durability of theThis is particularly important in high-sulphur

rubber and the durability of the adhesion

blending.

between the steel cord and the rubber.

This relationship has been the subject of much

Generally, rubber loses its strength due torecent research. Fig. 6.5 below shows the state

fatigue deterioration and heat deterioration as itof ageing rubber.

runs. If it were to come under significant stressin that state, the rubber layer would break andSlope = 0.75

the tyre would break down.

Non-running point
Type I(1) Breakdown Due to Ageing of the Rubber
Layer(80˚C and less)(120˚C and more)

The rubber covering the steel cord differs fromType II(100 ˚C~120 ˚C)ordinary rubber in that it has a higher sulphur

Type III

content. Where ordinary rubber has a sulphur
content of 1-2 parts per hundred rubber (phr),
this covering rubber has a higher blend of 3-6

Fig. 6.5. Changes in Physical Properties

parts phr to make it adhere to the steel cord.

(Modulus; 100% Mod.) During Rubber AgeingThis is because higher sulphur blends are betterand Correlation to Breaking Elongation λb 2)

at adhering to steel cord. However, the higher
the sulphur content, the more quickly the

The vertical axis in this chart represents therubber ages. Also, the higher the heat to which

breaking elongation logarithm (log λb) of

it is exposed, the quicker the speed of therubber, while the horizontal axis represents theageing. Since the onset of globalisation meansrigiditythat the same tyres are used throughout the(Ahagon plot). Generally, the elongationworld, there is a significant increase in thedecreases linearly with processing time, but if

usage

hotterthe processing heat is 80˚C or higher, the line

countries and colder countries from what there

moves by -0.75 (Type I on the chart). This

used to be. Age and deterioration happen moreindicates

quickly in warmer regions. Generally, once thebreaking elongation decreases. Further, asrubber ages, it becomes hard and its breaking

processing temperature increases, the slope ofelongation decreases. If there is a significant

the line increases (Type III on the chart). Typedecrease in breaking elongation, the rubber can

III occurs in the range of 80˚C or over up to

no longer handle deformation and the tyre

120˚C. While rigidity does not increase in thisbreaks down. In this sense, how hard the rubber

range, breaking elongation decreases. Thisis during use and how much the stretch has

indicates that elongation decreases more thantemperature

range

betweenmodulus

that

as

(100%

Mod)

cross-linking

logarithm

continues,

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through the advancement of cross-linking; the6.1.3. Decrease in Durability Due tomain polymer chains being severed. In other

Deterioration of Adhesion Between thewords, there is a great decrease in break

Steel Cord and the Rubber

elongation compared to the amount of Mod

Breakdown of tyres due to poor adhesionchange. When the amount of sulphur in the

between composite layers of different materials

rubbersuch as fibre and rubber, steel cord and rubberincreases,

ageingbecomesfaster;consequently, the straight-line decrease speed

has become a major issue.

increases. When it drops below a certain

In such cases, the area causing the breakdown

breaking elongation, there is an increased rateis such a small area volumetrically, such as theof tyre breakdown. Consequently, with highreaction layer in the adhesive interface, that thesulphur blends it is important to see how slowly

phenomenon occurs discontinuously, but it

they change; each company has its own special

causes major damage when it does happen. As

approaches to blending. Fig. 6.6 shows thethe tyre runs, the bonding layer and reaction

results for actual cars on the market. Here, thelayer in the adhesive interface deteriorate andelongation logarithm and Mod logarithm are

weaken, resulting in breakdown at some point

over -0.75. Running tyres and spare tyres (notin time. This deterioration is intensified by heat,running) are shown on the same line, showing

moisture or a combination of both.

that heat has a major impact 3). This method has

The steel cord and rubber are fastened together

made much recent progress as a measurable

by means of a surface brass plating (copper

method of evaluating rubber durability, both for(Cu) and zinc (Zn) alloy). When the tyre ismaterial in the laboratory and for rubber fromvulcanised (heated), the copper (Cu) in theactual car tyres. Type II is for cases of evenplating and the sulphur (S) blended into thehigher temperatures.

rubber(orcontaining
Running tyres
Spare tyres

otherintermediary

products

sulphur)undergochemicalareaction, producing copper sulphide (CuxS(where x = 1 ~ 2; either copper (I) sulphide orcopper (II) sulphide), zinc sulphide (ZnS), zincoxide (ZnO), etc., while the sulphur (S) bonds
with the rubber molecules, forming an adhesion
between the steel and the rubber.
If the plating is thick or has a high proportionof copper (Cu), the presence of moisturepromotes the production of CuxS, ZnS and

LOGMod 100 (Mpa)

ZnO, hindering adhesion due to a thick layer ofFig. 6.6. Changes in Physical Properties forbrittle reaction products. If moisture penetrates

Cars on the Market 3)

duringinitialassessment(directly

after
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vulcanisation) or during usage, the reactivity ofresorcinol, H: hexamethylenetetramine andthe plating becomes less than optimal. Whilesometimes

copper levels of around 70% are better for

problematic brands of tyres more commonly

initial adhesion, lower copper levels of aroundused RHS based accelerators, this was thought

63-65% are better if moisture is present.

to be the main cause of the issue. As later data

Breakdown of adhesion occurs more often

was taken into consideration, the main culprit

within the layer if the reaction layer is thick,

was found to be the over-reactivity of thesuch as in the model adhesion interface shownplating, with the accelerators an accessory atin Fig. 6.7.

most 16). The Cu/Zn plating at the time almost
Bonding point with rubber

Rubber sidesilica)based.

Sincethecertainly had a 70% copper proportion; thisPolymerwould have had a markedly higher reactivity

Adhesionreaction layer
Adhesion breakdown
within the reaction layer
Adhesion breakdown inplating crystals

Steel cord side

S:

Layer
Brass plating
layer (Cu/Zn)

Steel base

Brass
and
boundary

than the 63-64% proportion of today.
As shown in Fig. 6.7 above, the over-reactivity
would have produced a thicker reaction layer,steelwith breakdowns occurring both in the reaction

Fig. 6.7. Diagram of a Model Adhesion

layer and in the plating. This serious problem

Interfacewith steel radial tyres has now been almost
completely resolved, through much effort.

This figure is a combination of plausible

Generally speaking, breakdowns in steel radialmodels based on theories by van Ooij 4) 7), Morityres commonly start at the belt edges. The

10)

and

most common direction of travel of theothers. As shown in the figure, there are

breakdown is shown in Fig. 6.8. Breakdown

multiple areas for potential breakdown in the

begins at the belt edge (i.e., the end of the steeladhesion reaction layer; these breakdown areascord) and progresses from there.

, Pankaj9), Lievens8), Ishikawa

5) 6)

differ according to the usage conditions.
According to Watanabe, market issues withTyre edge cross-section

tyre breakdowns occurred from 1973 to around

Steel cord

1976, with many tyre companies around theworld

encountering

problems

withBreakdown(edge separation)

Origin of breakdown
Rubber layer

Direction of
separation

belt

separation (peeling around the belt area) causedby poor adhesion in steel radial tyres forpassenger vehicles. The main cause of the poor

Fig. 6.8. Model Breakdown of Belt Edgeadhesion was thought to be the adhesion
accelerator in the rubber. Two types of

6.1.4. Organic Fibre Cord Adhesion andadhesion accelerators were in use: cobalt (Co)

Fatigue Deterioration

fatty-acid based and RHS (blends of R:

While steel cord is used in the belts of radial
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passenger vehicle tyres, polyester or rayon are

a very tiny amount each time. The carcass isoften used in the carcasses. Recently, nylon has

subjected to bending and deflects, while

also often been used as a covering material overfluctuations in the tensile strength of the cord

the belt. In heavy vehicles (trucks and buses), it

within the carcass cause repeated shear strain in

is common to use steel cord for both the belt

the rubber layers between the ply.

and the carcass.

Under this behaviour, heat is generated

Carcass Adhesion

throughout the tyre, which is subjected to

Polyester

repeated deformation due to hysteresis loss; thisSince this fibre has poor chemical reactivity onheat gradually builds up. As a result, the entire

the surface and does not adequately adhere withtyre increases in temperature. Temperature

RFL, it is treated with either (1) a two-bathincrease has a doubly negative impact on themethod in which the surface is treated withlifespan of the tyre.

epoxy and then with RFL, or (2) a one-bath

The first negative impact is that as themethod in which a special adhesive is added totemperature rises, the materials from which the

RFL liquid and blends with the surface of thetyre is composed are subjected to highpolyester (see Fig. 6.9).

temperature, which reduces the lifespan of thetyre. The second negative impact is that with
RubberRubbercontinued high temperature, the tyre materials
gradually deteriorate through fatigue. On one
hand, the tyre is gradually losing its tread

low molecular RL

Epoxy

Polyester

Polyester

Polyester one-bathtreatment adhesive

Polyester two-bathtreatment adhesiveFig. 6.9. Model Adhesion Mechanisms 11)

rubber; on the other hand, it is losing overall
strength due to high temperature and fatigue.
As mentioned above, usage temperature isimportant for durability. The following aresome considerations on usage temperature.
1. Rubber decreases in strength under hightemperatures

6.1.5. Deterioration in Place Other than

2. Rubber ages more quickly under highAround the Belt

temperatures, meaning its strength and breaking

Fatigue deterioration also occurs in rubber

elongation decrease more quickly

outside of the belt area. For each revolution the

Rubber naturally decreases in strength andtyre makes, the entire area around thedeteriorates more when exposed to highcircumference of the tyre comes into contact

temperature. This means that tyres must have awith the ground each time, at which point thegreater breadth of heat tolerance now that they

entire tread area moves against the ground,are used throughout the world compared toexperiences fatigue and is worn away, albeit bywhen they were only used domestically. In
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other words, the scope of performance for use

complex, as it varies according to manyin just one country is no longer enough; tyres

different contributing factors. Broadly speaking,need a greater range of durability. In highhowever, it depends on the friction force on thetemperature regions, there was often trouble

wheel tread. A tyre travelling at a fixed speedwith accelerated deterioration due to heat; it

without

took time to resolve this.

cornering or other major friction on the treadanyaccelerating/decelerating,incurs hardly any wear. In other words, the6.1.6. Accidental Tyre Failure

greater the friction force on the tread and the(1) Cut Burst and Shock Burstroad surface, the greater the susceptibility to

A cut burst is a burst caused by a stone or

wear. The difference in wear life between

similar severing the cord and the tyre no longer

vehicles is given as follows 12).

being able to contain the air pressure. A shock
burst is a burst caused by a significant force on

Approximate Wear Life Values 12)

the cord, such as an impact from travelling overCategory

Wear Life
30,000-60,000km

a bump, and the cord layer breaking down

Steel

Generalwithout being severed.

radialpurpose tyre

Usually these occur on unpaved roads, but eventyres forHigh

on paved roads a tyre can run over an obstacle

passenger

performancesuch as stone and, enveloping it, deform. If thevehiclestyreobstacle is small, then the tread rubber can

SteelTransport

form a localised deformation around it, but if it

radialtruck

is larger, even the carcass could deform aroundtyres forBus

100,000-200,000km

it. The tyre is affected by the size, shape andtrucks

Dump truck

50,000-100,000km

surface friction coefficient of the obstacle,

and buses

20,000-30,000km

200,000-300,000km

which alters the degree of stress concentration,
deformation, impact resistance and other

The main causes of significant friction between

factors applied to the tyre, depending on thetyres

level of air pressure in the tyre, the strength ofaccelerating/decelerating and (2) cornering

the carcass, running speed and other conditions.

(turning).

This occurs in dump trucks, construction(1) Subjected to Acceleration/Deceleration

machinery and other vehicles currently running

The distribution of contact pressure along theon unpaved roads.

circumference of the tyre is shown in Figs. 6.10

and

the

road

surfaceare(1)

and 6.11.
6.1.7. Wear Resistance

These figures indicate that the higher the load,

As the tyre runs, the surface is worn away. The

the higher the contact pressure at both ends. Fig.

phenomenon of wear on the tread is extremely

6.11 indicates that high contact pressure occurs
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during

acceleration/deceleration

in

the

(Horizontal) schematic view (the area directly

longitudinal direction (fore-and-aft direction)

after pressing in and directly before pressing

when it is pressing in or pressing out. When theout is lower under lighter loads and higher

tyre is accelerating/decelerating, the entire tyreunder heavier loads)

slips. The surface of the tread has traction areasand smooth areas; these are caused by wear.

(2) Subjected to Lateral Forces Due to

In an extreme situation, such as the tyres

Corneringlocking and being dragged along, or the tyres

When a car takes a corner while moving

are spinning, there are no traction areas. Wear

forward, the tyres slip sideways and lateralon the tyre occurs on the smooth areas.

force is produced to counter the centrifugal

Accordingly, conditions that increase theforce. Away from the contact surface, thesmooth areas, such as acceleration or sudden

lateral force is of course 0, but within thebraking, make the wear on the tyre markedly

contact surface there is a disconnect between

prominent.

the direction of travel of the tyres and thesurface of revolution due to the slip angle andContact pressure (kg/cm2)

Heavy load
100% load

the centre lines of these two factors separate.
To begin with, the tread gains traction on theroadLight load

surface

and

there

is

no

relativedisplacement between it and the road surface.
As the deformation of the tyre increases and theShoulder ¼ point

Centre ¼ point

ShoulderFig. 6.10. Characteristics of Contact Pressure in
Passenger Vehicle Tyres

13)

rightening force increases, the adhesive force
between the tread and the road surface cannot
be maintained and the tread starts to slip. At the(Horizontal) schematic view (the shoulder area

rear end of the contact area, the carcass centre

is lower under lighter loads and higher under

and the tread centre line up (see Fig. 6.12). This

heavier loads)

action is repeated at every point on thecircumference of the tyre. Wear on the tyre is
generated is the slip areas. The further theContact pressure (kg/cm2)

Heavy load

steering wheel is turned, the greater the slip

100% load

angle, which increases the lateral force and also
increases the wear on the tyres.

Light load

As this wear progresses, the pattern eventuallydisappears. It is desirable that the tyre fulfils its
Pressing out

lifespan without the case, which is the skeletal

Fig. 6.11. Characteristics of Contact Pressure in

structure comprising the belt and carcass,

Passenger Vehicle Tyres 13)

breaking down.

Pressing in

Directly under load84
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Since tyres are principally made of rubber, it

Throughout the long history of tyre technology,

should be possible to predict reasonable limits

this is one area that remains to be resolved.

with an understanding of the stresses applied to

While various wear evaluating machines haveeach area. However, the rubber and the fibre

been developed for use in laboratories in Japanare both high molecular substances and are

and around the world, these are by no means

subject to thermal and mechanical strength loss

conclusive.

and fatigue deterioration due to increases intemperature from dynamic deformation as well

Radial tyre durability is a major issue. In

as repeated mechanical loading; determining

particular, the trouble with adhesion between

the allowable stresses is not straightforward.

the steel cord and the rubber has been a major

Technology related to wear has mostly

problem worldwide. Many researchers haveaddressed

devoted much research into solving this.

the

wear

itself,involvingdevelopments to improve the constitution ofmaterials, while irregular wear that involves

6.1.8. Run-Flat Tyres

partial wearing has largely been dealt with by

A New Proposal for Durability

measures taken in structural design.

Countermeasures against incidents such as

Wear-related

mechanisms

complex

quite

and

are

difficultextremely

punctures have always been considered withtodriver safety as an underlying issue

Lateral displacement (mm)Lateral force

assess.

Adhesive force

Tread line

Slip area (Wear occurs in this area)

Traction area

Direction of rotation of the tyre

Slip force

Carcass line
Contact
area

Starting Directly End point
point under load (pressing
Slip angle(pressingout)in)Direction of travel of the tyre

Above

Fig. 6.12. Schematic Diagram of Lateral Deformation and Lateral Force Distribution on a Tyre
While Cornering 14)

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Tyre cross-section
Existing productRun-flat tyre

Shape at normal
air pressure

Shape at 0kPa airpressure

Shape at 0kPa air Side reinforcing
rubberpressure

Fig. 6.13. Run-Flat Tyre 15)

Run-flat tyres are tyres that can travel

countermeasures are not uniquely Japanese

temporarily even with air pressure at 0 (see Fig.

technology. Japanese technology in this area

6.13). This is made possible by means of side

includes: (i) progress on the countermeasures

reinforcing rubber fitted into the inner tyreagainst the significant problem of steel

structure. While this method increases theadhesion (of course, this happened in otherweight of each tyre by the amount ofcountries as well); (ii) the proposal of thereinforcing rubber used, the overall weight ofpredominancethe vehicle decreases as it does not require aevaluation method (Ahagon plot); and (iii)

spare tyre. There is also a significant benefit toprogress on run-flat tyres, among others.

the user in that not carrying a spare tyre means

Durability is not an issue that changes with themore space inside the vehicle.

demands of the times; it must of course beofarubberdeterioration

maintained. It is vital in the environmental age
6.1.9. Summary

to prolong the lifespan of tyres; while it is not

As discussed above, the issue of durability isat the obvious forefront of performance, it is

not unique to Japan alone. Accordingly, thegrowing in importance.

Cited references:
1) Hattori, Rokurō: Taiya no Hanashi [The Story of the Tyre], Taiseisha, June 1992, pp. 92-94.
2) A. Ahagon, Rubber Chemistry and Technology, 59, p. 187, 1986.
3) J. M. Baldwin, D. R. Bauer and P. D. Hurley
Presented at a meeting of the Rubber Division American Chemical Society.
Columbus, OH, 5-8 October 2004.
4) W. J. van Ooij, Rubber Chemistry and Technology, 57, p. 421, 1984.
5) Ishikawa, Yasuhiro: Journal of the Society of Rubber Science and Technology, Japan, 45, p. 921, 1972.
6) Y. Ishikawa, Rubber Chemistry and Technology, 57, p. 855, 1984.

86
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7) W. J. van Ooij, Kautschuk Gummi Kunststoffe, 44, p. 348, April 1991.
8) H.Lievens, Kautschuk Gummi Kunststoffe, 39, p. 122, February 1986.
9) Patil Pankaj Y. and Ooij W. J, Rubber Chemistry and Technology, 79, p. 82, 2006.
10) Mori, Kunio; Kin, Saisō and Takaomi Yasukawa: Journal of the Society of Rubber Science and Technology,
Japan, 67, p. 293, 1994.
11) Rewritten from Jidōsha-yō Taiya no Kiso to Jissai [Foundation and Reality of Automobile Tyres], Bridgestone
Corporation, ed., Sankaido, January 2006, p. 293.
12) Watanabe, Tetsuo: Taiya no O-Hanashi [The Story of the Tyre], Japan Standards Association, October 2002,
from p. 114.
13) Hattori, Rokurō: Taiya no Hanashi [The Story of the Tyre], Taiseisha, June 1992, p. 87.
14) Hattori, Rokurō: Taiya no Hanashi [The Story of the Tyre], Taiseisha, June 1992, p. 88.
15) “Gomu Erasutomā to Kankyō [Rubber Elastomers and the Environment]”, Rubber Technology Forum, ed.,Journal of the Society of Rubber Industry, Japan, 2008, p. 104.
16) Watanabe, Tetsuo: Taiya no O-Hanashi [The Story of the Tyre], Japan Standards Association, October 2002, pp.
89-90.
17) Hattori, Rokurō: Taiya no Hanashi [The Story of the Tyre], Taiseisha, June 1992, p. 114.

6.2. The Age of Manoevrability: The

overseas

Coming of Age of Radial Tyres in the Age ofadopted after the war, new materials and new

Manoeuvrability

structures, the shift from bias to radial and thetechnology:

overseas

technology

shift from tube to tubeless. In the new era,
6.2.1. Rubber Development for RollingJapan made huge contributions by using its

Resistanceown technology to make fine optimisations.

Since radial tyres are made using steel cord,

Many design elements related to durability

which is quite a different material from rubber,were material factors rather than structural

poor adhesion made for significant durability

design factors. However, manoeuvrability notissues. Many researchers worked to overcome

only incorporates material elements such as

this issue. The time that followed, from therolling resistance (fuel consumption) and1980s onwards, was the age of manoeuvrability.

friction (grip), but also structural design

It was from around this time that distinctly

elements for cornering performance, such as

Japanese tyre products and technology began tostability and controllability. In other words,

emerge. Looking back at the course of tyremanoeuvrability is an area encompassing bothtechnology in the post-war era before that, itmaterial factors and structural design factors.

was a time of incorporating and learning
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(1) Contribution of Rubber to Rollingroad surface and the tyre tread. Thus, let us

Resistanceconsider rubber friction.

As the rolling resistance of a tyre decreases,
fuelconsumption

improves.

Inthe(2) Rubber Friction

environmental age, there is a demand to reduce

The phenomenon of friction between rubberrolling resistance to improve fuel consumption.

and a solid surface differs completely from that

The contribution of each part of the tyre toof friction between ordinary solid surfaces.

rolling resistance is as shown in the following

Rubber has a friction coefficient that decreases

figure. Since tread contributes half of the total,as the contact pressure increases; it also relates

countermeasures have been focused on tread.

to the relative sliding velocity and temperature.

Tyre 165R13

The friction coefficient is greatest when sliding

Other
Belt 7%8%
Bead 11%
Tread 49%
Carcass
11%
Side
14%

at a relatively slow velocity rather than in astate of rest.
Fig. 6.15 shows a model of friction.

Friction F

Load
RubberFig. 6.14. Proportion of Contribution made by
Each Part of a Tyre to Rolling Resistance 1)(according to the finite element method)
Accordingly,

treadrubberhas

becomeimportant to developments related to rolling
resistance. That is to say, a demand has grown
for low energy loss materials to be used in tread
rubber.

Hysteresis force FH
Adhesive force FA

Fig. 6.15. Factors in Rubber Friction 3)

On the other hand, high energy loss is required

When a rubber mass presses against anotherfor proper braking performance on wet roads

solid mass under normal force and slides alongand similar. Consequently, if low energy loss

the interface, an adhesive force acts between

rubber were to be used in place of existing tyre

the masses through molecular attraction on therubber, braking performance would decrease.

contact surface and resists sliding. If the surface

In other words, there is a trade-off in which theof the solid mass is uneven, the rubber tries toenergy loss has to be as low as possible while

fill out the unevenness by compressive

running and as high as possible while braking.

deformation because of its low elasticity.

From the perspective of tread rubber, braking

Consequently, when sliding occurs along theperformance is the issue of friction between theinterface, the areas on the rubber colliding with
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the convex areas on the solid surface aresubjected to compression; when it encounters

The greater the friction force, the more difficult

the other side of the convex areas or the

rolling becomes; the higher the resistance to theconcave areas, the rubber is released from thatrolling of the tyre, the worse the fuel efficiency.

compression or stretches the opposite way. The

Fuel efficiency and safety are mutuallydifference in deformation energy coming andexclusive phenomena. In other words, as

going through localised repetition, that is,mentioned above, there is a trade-off between

hysteresis loss, acts as friction and is consumed

low rolling resistance (LRR) and frictionin the form of heat energy; the corresponding(particularly wet friction). Easier rolling means

frictional force acts on the interface.

harder stopping. Currently, it is increasingly
more common to aim for both summer/winterIn other words, total friction = hysteresis force

performance (high grip in high or low(FH) + adhesive force (FA). Some friction,

temperature regions in wet or dry conditions)particularly Wet μ (friction coefficient of a wet

and LRR wear resistance. Achieving both low

road surface), has a very high hysteresis loss

fuel consumption (low rolling resistance) andeffect. Hysteresis friction is dependent on thehigh braking performance (grip) has been aviscoelastic properties of the rubber, such as its

major topic of research addressed by manytan δ (hysteresis element; the tangent of theresearchers since the 1980s.

phase difference δ between vibration stress andvibration strain) and E’ (modulus of elasticity).

The time-temperature superposition principle

The viscoelastic property is not fundamentally

was used to solve this trade-off. This principle

a breakdown phenomenon, but rather afollows the idea that temperature and time canresponse to the strain (deformation) that is

be transferred in high molecular substances; therepeatedly applied to the rubber; it depends on

physicalthe properties of the overall volume rather thancorrespond to high-speed (high frequency)

on the properties of miniscule areas. With

deformation, while the physical properties atconsideration for blending compounds, thehigh temperatures correspond to low-speed

greater the volume of a compounding element(low frequency) deformation. The objective

in relation to the whole, the greater the impact

function uses tan δ, the delay function of theof that element. Usually, in sequence of volume,

response

the most used material is natural or synthetic

resistance is the resistance acting every time theraw rubber (polymer), followed by carbon

tyre rotates, it is the resistance against one

black, silica or other reinforcing agents.

deformation per rotation. This equates to a

Accordingly, in an age where manoeuvrability

frequency of 10Hz (low speed). Meanwhile,is in demand, development is focused on raw

braking (grip) incurs a reciprocating motion inpolymers and reinforcing agents.

which

properties

toatstimulus.

deformations

low

Since

are

temperatures

therestoredrollingagainst89

National Museum of Nature and Science
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protuberances in the surface of the road. In this(BR) rubber would lower tan δ at 60˚C, it

case, as the tyre follows minor unevenness inwould also lower tan δ at 0˚C. The peak of the

the

of

tan δ curve lies at Tg (glass transition

thetemperature; the temperature at which theunevenness falls between several tens ofrubber state starts to congeal into a glassy state).

thousands to several million Hz (high speed).

Consequently, if rubber with a high Tg is used,

Accordingly,

resistancetan δ at 0˚C rises, but tan δ at 60˚C also rises.

corresponds to tan δ of high temperatures andOn the other hand, using a lower Tg, such as

grip corresponds to tan δ of low temperatures,the aforementioned BR, lowers tan δ at 60˚C,they are generally measured as tan δ at 50-60˚C

but also lowers tan δ at 0˚C. SBR is often used(rolling resistance) and tan δ at 0˚C (Wet grip),to address both factors. While emulsion-SBR

which quickly developed into a tan δ curve. See(E-SBR) (emulsion polymerisation; radical

Fig. 6.16.

polymerisation) is generally used, anotherroad

surface,thedeformation/reformation

since

speed

againstrolling

method is to use solution-SBR (S-SBR)
Wet skid resistance

Rolling resistance(solutionpolymerisation;

anionic

polymerisation), which provides an evensteeper tan δ curve at 0˚C and 60˚C (see Fig.
6.17).
Frequency
Wet skid resistance

Rolling resistance

Wet skid resistance

Rolling resistanceTemp. (˚C)

Temperature

Frequency

Fig.

6.16.

Fig. 6.17. Relationship between tan δ andTemperatureandFrequency

Dependency of tan δ and its Relationship to

Temperature for Various Kinds of Synthetic
Rubber 6)

Required Tyre Properties 2)
Reducing the amount of carbon is another
From the above, there is a need to reduce tan δ

known method of steepening the tan δ curveat 60˚C in order to reduce rolling resistance. To

that is widely used 5).

achieve this requires a low energy loss material.
While using existing low energy loss tyre(3) SBR plays a significant role in passenger

rubber such as natural rubber or polybutadiene

vehicle tyres, such as in the development of
90

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synthesis technology for passenger vehicle

Tg polymer with a low styrene content;tyre rubber.

however, this also reduced tan δ near 0˚C,

It has brought immeasurable diversity to rubber

meaning a decrease in Wet grip μ. The S-SBR

compounding. This is because SBR can be(solution-polymerisation SBR) method was

freely designed in terms of its microstructure,

introduced as it offered a way to solve thismodification and other factors. Thus, SBR

trade-off using polymer molecular design.

makes it possible to have a variety of molecular

Incorporating molecular design with S-SBR

designs, ushering in an age of designer

made it possible to plan the tan δ curve.

compounds through detailed molecular design

Acquisition of S-SBR technology and, by

in order to steepen the tan δ curve (1980s, see

extension, terminal-modification technology,

Fig.

made a significant contribution to technology

6.18).

The

shift

from

radicalpolymerisation (emulsion polymerisation) tofor reducing rolling resistance.

anionic(solution

At this time, methods for steepening the tan δ

polymerisation) during this time gave a greater

curve were worked on together by researchersdegree of flexibility in molecular design, asaround the world. Tyre companies did not havefollows.

their own individual theories. Competition

polymerisation

focused on the different effects achieved
through the choice of materials used and the

SBR molecular structure

Terminalmodification

mixing design.
During this time, Japan devoted much research
to technology for optimising combinations.
Japanese rubber technology made a significant

Styrene(hard portion)

contribution to this field. The two oil crises in

Butadiene
Vinyl(soft portion) (hard portion)

the 1970s and later environmental issues
resulted in the need for low fuel consumption,

Fig. 6.18. SBR Microstructure

which in turn drove a flurry of research on
modified SBR to improve fuel economy.

1. styrene content; 2. vinyl content; 3.
molecular

modification(4) Molecular Modification Technology(terminal-modification); 4. molecule weight; 5.

The catalyst for anionic polymerization ismolecular weight distribution; 6. sequence

usually

distribution (styrene sequence distribution)

n-butylithium,

Sinceradicalvariationinpolymerisation
styreneallowscontent,

forradicalorganolithiumetc.).

(alkyllithium;

Since

these

are

living-polymerisable (the ends continue in a
state

of

live

catalytic

activity

duringpolymerisation could be used to control rolling

polymerisation),

resistance (fuel consumption) by using a lowinterrupted, it will continue its catalytic activity.

ifpolymerisation

is

not

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In binding mode, it is important to control theKneading

styrene content, which serves as a rigid element
for modifying Tg, as well as the vinyl content(too much will raise the Tg). In anionic

C/B

Sn modified polymer

polymerization, the vinyl content can becontrolled either by adding ether compounds,
amine compounds (vinylation agents) or othercompounds

duringpolymerisationorBound rubber

bycontrolling the polymerisation temperature.

Fig.

6.19.

Model

of

Improved

Carbon“Molecular terminal-modified rubber can be

Distribution with Sn Modified Polymer 9)

obtained by adding or reacting a modification
agent to the active terminals at the final stage ofModified polymer compounding techniques

anionic

using

have become the axis of tread formulation foralkyllithium as a medium, then stopping theboth fuel economy and wet grip. This

reaction with ordinary methanol or similar.

technology was developed to provide a means

This binds with the surface of the carbon in theof binding rubber molecules and carbon

rubber, mutually binding carbon to carbon,

together to restrict free movement of the carbon,

thereby reducing the friction between carbons,as the carbon/carbon friction needs to belowering the tan δ and suppressing heat

reduced in order to lower the tan δ (reducing

generation. N-alkyl benzophenones and N-alkyl

loss and heat generation) of carbon-containing

lactams are effective modifiers.” (Technology

rubber, as outlined above.

by Zeon Corporation et al. 8))

Accordingly,

Further, during polymerisation, once 100% of

research was devoted to technology that would

the monomers have converted to polymers, it isintroduce a functional group with affinity forpossible to make use of the fact that the

carbon at the middle of the polymer and at thepolymer terminals are active, adding tin, siliconterminals. Noguchi 7), Nagata 8), Ohshima 12),or other halides or divinylbenzene to cause a

Tsutsumi 13) and other researchers confirmed

coupling reaction and change the molecular

the effect of polymer terminal modification onweight distribution. This technology was

lowering rolling resistance. As shown in Fig.

largely researched and developed in Japan 9).

6.19, the idea was to efficiently modify theFig. 6.19 shows a model of coupling andpolymer terminals and increase the affinity ofchange in molecular weight distribution due tothe polymer terminals to carbon. In any case,tin tetrachloride. (Technology based on Japanthe idea was to reduce the main viscosity factor

Synthetic Rubber, etc.)by removing the free terminals. Many patentorlivingpolymerizationas

discussed

above,

much

applications have also been made in relation tothis 14).
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low-temperature kneading processes, because(5) The Age of Silica
Since

1990,

an

the
increasing

amountsilanecoupling

agent

used

has

a

of

cross-linking reagent structure and if it gets too

technology has switched some of the carbon for

hot during mixing it will react and become

silica, for the purposes of both fuel economy

solidified (burning). To suppress this reaction,

and wet skid performance. Silica has a

it was found that a mixer with a mesh rotor hadhydrophilic silanol surface, which makes it

a better cooling effect than existing mixers, so

difficult to disperse through rubber and prone

silica mixers are being switched to this type 10)

to clumping. Consequently, it is more difficult

11).

than carbon to distribute evenly throughout therubber. To assist with this, a silane coupling
agent is used to alter the surface of the silica,
which improves its dispersion and also causes areaction between the silica and the rubber to
Carbonform a bond (primary bond). A lower rolling
resistance is obtained by effectively reducing
the heat generation caused by contact between
silica. This method means the rubber is morerubbery, which gives tan δ a higher peak; it also
raises tan δ at 0˚C from the perspective of Tg,

Temperature (˚C)

which means that silica provides a steeper tan δ

Fig. 6.20. Temperature Dependency of tan δ ofcurve than carbon, improving both the rolling

Carbon and Silica 4)

resistance and the wet grip at the same time.

5% DSA 10Hz carbon; N234 silica (+TESPT;

Fig.

coupling agent) base mixture; S-SBR (high

6.20

shows

a

comparison

of

the

viscoelastic properties of materials made fromvinyl SBR75/BR25) filler 80 phr oil 32.5

carbon compounds and from silica compounds.
Research

has

also

continuedonthe(6) Silica Modification Technology 19)

viscoelasticity of silica 10). Its use has expanded

Technology was also developed to modify

throughout the world since the early 1990s,

polymers to facilitate the bond with silica, likewhen Michelin announced its use in green tyres.

the bond between carbon and polymers.

It also grew rapidly in popularity due to its(i) Modification for Silica

conformity to environmental measures (reduced

Research to introduce a functional group to

CO2 due to lower fuel consumption). Many

SBR that would mutually interact or bond withresearchersinsilica particles resulted in the development of. Much research has

typical modified SBRs for blending with silica,

also been carried out around the world onsuch as diglycidyl amine compounds, cyclic

haverelation to thiscontributed15) 16) 17) 18)

research

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imine compounds, halogenated alkoxysilane
compoundsatthelivingterminaloralkoxy-modified SBR. SBR with terminals
processed

by

this

functional

group

Base (carbon compound)(Silica compound)
Silica compound +terminal-modified SBR)
Rolling
Temperature (˚C)
resistanceareconfirmed to have an increased tan δ at 0˚C and
Wet skid
resistancea decrease at 50-60˚C 20).
Fig. 6.21 below shows the effect of modified
polymer rubber on tan δ at 0˚C and at 50˚C.

Fig. 6.22. Changes in tan δ Curve (Model) fromThe effect of both terminal modifier processes

Carbon Compounds → Silica Compounds →is clearly seen against the unreacted substance

Modified Silica Compounds

20).

tan δ at 50°C
rolling resistance → improved

Direction of
improvement

Manypatentapplicationsformodifyingpolymers for silica have been filed from Japan19).

It is fair to say that Japan was demonstrating its
prowess in the technology at the time,
5 types of modifiers
Unmodified SBR Processed SBR

particularlyinterminal

modification

technology as a means of intricate mixing
design. While the epoch-making technology ofcompounding solution-polymerised SBR andtan δ at 0°C
wet skid resistance → improved

using silica did not originate in Japan, Japan

Fig. 6.21. Improved Fuel Economy and Wet

was very quick in developing, optimising andGrip

implementing it.

Performanceof

Various

Kinds

ofModified SBR 20)
6.2.2. Structural Design Elements forThis figure shows that SBR modified byManoeuvrability

reacting

with

a

by

anionic(1) The Effect of Aspect Ratio

polymerisationhasstrongermutualAs the transition to radial tyres progressed,

bettertyres with a low aspect ratio became more

distribution of the silica particles. At present,

popular, particularly for high performance tyres,the most effective method is a combination ofin order to improve manoeuvrability. All tyres

switching carbon for silica and modifying thecame to adopt a lower aspect ratio, even

SBR. Fig. 6.22 shows a model of how these

non-high-performance tyres, as the wider width

affect tan δ.

andinteractionwithmodifiertheasilica,

with

lower

heightgave

them

bettermanoeuvrability (Fig. 6.23 (A) (B)).

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Flattening

Low aspect tyre

Aspect ratio =length/width
Width

Ordinary tyre

LengthSmaller angle

Greater angle+ 2 inches- 20%+ 20mm+ 1 inch- 10%+ 10mmSize fitted on a new car
Aspect ratio
Tyre widthFig. 6.23 (A) Effect of Aspect Ratio 21)

Ordinary tyre

Low aspect tyre

Flattening the cross-sectional shape of the tyre
results in tyres with wider tread, producing
greater cornering force. This is due to greater
flexural rigidity of the tread, since the width of
the belt area increases in accordance with theForce fromthe side

tread width. The cornering power (the slope ofForce fromthe side

the straight line section of the cornering force)
also increases.

Greater distortion

Less distortion

Fig. 6.24 below shows aspect ratio andcornering power. The smaller the aspect ratio,
the greater the cornering power. This gives theFig. 6.23 (B) Structural Change due to a Lower
Aspect Ratio

21)

driver a sense of agility in the operation of thesteering wheel while driving.

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National Museum of Nature and Science
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performance are a combination of material
50 series(205/50R16)

Cornering Power

Air pressure:
200kPadevelopment in the form of controllingviscoelasticity and structural development in

60 series(195/60R15)
70 series(185/70R14)
82 series(165R14)the form of ratio flattening. In other words, this
aspectoftyre

technology

development

encompasses both materials and structure.
Japan’s contribution to tyre development
prompted development in the high-performancetyre

category,making advancesin tyreflattening. However, tyre flattening broughtwith it a new problem: poor fuel economy.
Load (kN)

Fig. 6.24. Tyre Aspect Ratio and Cornering
Power

22)

As

discussed

in

this

section,while

developments in manoeuvrability performance
such

as

silicatechnology

andanionic

polymerization did not originate in Japan,
Sports cars and other high performance

Japan did absorb the technology and added to it

vehicles are fitted with 50 series, 40 series andin areas such as terminal modification, which

other tyres with a lower aspect ratio, as they

made Japanese tyres world class.

require greater turning power, not only while

In particular, there were major developments inturning at high speed, but also while travelling

polymerisation technology among polymer

straight. A lower aspect ratio means a larger

manufacturers. The material and structural

rim diameter for the same outer diameter,

designs of the time indicate that the level ofwhich means larger brake discs and othertechnology was rapidly increasing, particularly

fittings can be fitted, which has the advantage

among Japanese tyre manufacturers, who wereof being good for braking performance. In

becoming more well-balanced in all areas ofreview,

performance.

developments

inmanoeuvrability

Cited references:
1) Gomu Kōgyō Binran [Rubber Industry Handbook], fourth edition, The Society of Rubber Science and Technology,
Japan, ed., January 1994, p. 750.
2) Ozawa,Yoichi: High Polymers,Japan,Vol.54, 2005, p.750.
3) Desmond F. Moore: The Friction of Pneumatic Tyres, Elsevier Scientific Publishing Company, Amsterdam,
Oxford, New York, 1975, p5.
4) Rewritten from Meng-Jiao Wang, “Effect of polymer -Filler and Filler –Filler Interaction on Dynamic Properties

96
National Museum of Nature and Science
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of Filled Vulcanizates”, Rubber Chemistry & Technology, 71, 1998, p. 520, Fig. 47.
5) P.P.A. Smit: Rubber Chemistry & Technology, 41, 1968, p. 1194.
6) “Gomu Kōgyō ni okeru Gijutsu Yosoku — Jidōsha taiya wo Chūshin ni shite [Technology Forecasting in the
Rubber Industry: Focus on Automobile Tyres]”, Rubber Technology Forum, ed., December 1990, Posty
Corporation, p. 110.
7) Noguchi K., Yoshioka A., Komuro K.: Presented at Meeting of Rubber Division, A.C.S. New York (1986)
8) Nagata, Nobuo: Journal of The Society of Rubber Science and Technology, Japan, 62, p. 630, 1989.
9) “Gomu Erasutomā to Kankyō [Rubber Elastomers and the Environment]”, Rubber Technology Forum, ed.,Journal of the Society of Rubber Industry, Japan, p. 134, cited from Yoichi, Ozawa: Kōbunshi [High Molecular],
54 750 (2005).
10) Matsuda, Takaaki: Journal of The Society of Rubber Science and Technology, Japan, 78, p. 46, 2005, etc.
11) Moribe, Takashi: Journal of The Society of Rubber Science and Technology, Japan, 74, p. 70, 2001.
Moribe, Takashi: Journal of The Society of Rubber Science and Technology, Japan, 81, p. 509, 2008.
Yamada, Norifumi: Journal of The Society of Rubber Science and Technology, Japan, 81, p. 516, 2008, etc.
12) N. Ohshima, F. Tsutsumi, M. Sakakibara: International Rubber Conference 1985, Kyoto.
13) Tsutsumi, Fumio; Sakakibara, Mitsuhiko; Oshima, Noboru; Fujimaki, Tatsuo; Hamada, Tatsuro: Journal of The
Society of Rubber Science and Technology, Japan, 63, p. 243, 1990.
14) Patent application numbers:
Sho-59-196337 (Zeon) Benzophenone terminal treatment; Sho-61-042552 (Zeon) terminal modified SBR;
Sho-61-225228 (Zeon) Terminal tin modification; Sho-63-122740 (Zeon/Yokohama) Amino benzophenone
terminal treatment; Sho-63-66246 (JSR/BS) Tin terminal-modified BR; Sho-63-118343 (JSR/BS) Vinyl aromatic
amine terminal modification; Sho-63-139902 (Sumitomo Chemical) Nitro compound terminal modification;
Sho-63-179949 (JSR/BS) Specific S-SBR tin coupling; Sho-64-040503 (JSR) Terminal tin amine modification;
Sho-64-62341 (JSR) Sn terminal modified BR; Sho-64-69645 (JSR) terminal-modified branched SBR;
Sho-64-118343 (JSR/BS) Nitrogen-containing vinyl compound terminal modification; Sho-64-22940 (JSR/BS)
Amino-group-containing unsaturated compound copolymers or terminal-modified BR or SBR; Hei-01-146937(Zeon/Yokohama) Amino benzophenone terminal treatment; Hei-01-146939 (Yokohama/Zeon) Amino
benzophenone terminal treatment; Hei-01-158056 (Yokohama/Zeon) Amino benzophenone terminal treatment;
Hei-01-135844 (JSR/BS) terminal modification by high trans tin coupling; Hei-01-35847 (JSR/BS) high transbutadiene (BR or SBR) function tin coupling terminal modification; Hei-6-279515 (JSR) Reacting tin
compounds, etc. with active polymer terminals; 2000-159813 (Ube) Synthetic diene rubber modified with asilanol or amine; 2004-276686 (Toyo) Butadiene rubber modified with benzophenone, thiobenzophenone,
isocyanate compounds or halogenated tin compounds; 2005-146115 (Sumitomo) Modification with alkoxysilyls
and/or glycidyl amines; 2007-31722 (Ube) amine-terminal-treated BR; 2007-161798 (Ube) Modification by asilicon compound having an alkoxy and an amine; 2007-169558 (Sumitomo) Diene rubbers modified by alkoxies
or alkoxy silyls.

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Abbreviations: Zeon: Nippon Zeon; BS: Bridgestone; JSR: Japan Synthetic Rubber; Sumitomo: Sumitomo
Rubber; Yokohama: Yokohama Rubber Company; Toyo: Toyo Rubber; Ube: Ube Industries.
15) Payne A.R., Whittaker, R.E.: Rubber Chemistry and Technology, 44, p. 440, 1971.
Hans-Detlef Luginsland: Applied Technology Advanced Filler Harry-Kloepfer Rtr.1 50997, Cologne Federal
Republic of Germany, Cologne, October 2002.
16) Yingbing Li, M.J. Wang, Tao Zhang, Fenbou Zhang and Ximei Fu: Rubber Chemistry and Technology, 67, p.
693, 1994.
17) Minagawa, Yasuhisa: The Society of Rubber Science and Technology, Japan, Abstracts from the 16th Elastomer
Symposium, p. 68, 2003.
18) Kabe, Kazuyuki; Suzuki, Nobuo; Miyashita, Naoshi: Journal of The Society of Rubber Science and Technology,
Japan, 2002, p. 79.
19) Patent applications (silica + modification related): patent numbers:
Hei-11-209519 (Yokohama) Polymer SBR modified with benzophenone, isocyanate, halogenated tin, etc.;
2002-103912 (BS) Alkoxysilyl modified diene rubber; 2005-126556 (Sumitomo) SBR terminal modified bycarboxyls and hydroxyls; 2005-146115 (Sumitomo) Alkoxy glycidyl amine-modified SBR; 2005-336347 (BS)Hydroxyoxindole silane compound-modified SBR; 2006-160884 (BS) Modified conjugated diene polymer
having two or more functional groups containing nitrogen in the molecule; 2009-2635586 (BS) Modified
conjugated diene-based copolymer having protic amine or amine protected by an eliminable functional group in
the molecule; 2009-280805 (BS) Amine functional group-modified polybutadiene rubber, rubber having ahydrocarbyloxysilane and an amine; 2010-209254 (JSR) Alkoxysilane compound reaction modified SBR;
2010-168469 (BS) Modified conjugated diene polymer rubber having a nitrogen-containing functional group at
the terminal and having a silicon atom-containing functional group in the polymerisation terminal.
Abbreviations: BS: Bridgestone; JSR: Japan Synthetic Rubber; Sumitomo: Sumitomo Rubber; Yokohama:
Yokohama Rubber Company.
20) Rewritten from “Gomu Erasutomā to Kankyō [Rubber Elastomers and the Environment]”, Rubber Technology
Forum, ed., Journal of the Society of Rubber Industry, Japan, p. 136, Figs. 4-26. Matsuda, Takaaki: Journal of
The Society of Rubber Science and Technology, Japan, 78, p. 46, 2005.
21) (A) Best Car, ed., Taiya no Subete ga Wakaru Hon [The Book that Tells You Everything You Need to Know About
Tyres], Sansuisha, Kodansha, 2008, p. 87.
(B) Gomu Nenkan [Rubber Yearbook], Japan Rubber Weekly, 1983 edition, November 1982 , p. 62.
22) Jidōsha-yō Taiya no Kenkyū [Studies on Automobile Tyres], Yokohama Rubber Company, ed., April 1995, p.
139.

6.3. The Age of Sensation and Sensitivity:

Age of Sensation and Sensitivity

The Coming of Age of Radial Tyres in the98
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6.3.1. Perception of the Times in the Agetechnology can be said to have reached a highof Sensation and Sensitivity

level. This relates to the increasing focus on

The course of development of radial tyres

fuel economy and other environmental issues as

discussed in the preceding sections has seensociety has advanced.

some remarkable progress, with a wealth ofWith the advent of the age of sensation andresearch resulting in significant improvements

sensitivity, recent development has taken thein durability, rolling resistance (fuel economy)

form of durability + manoeuvrability +and aspects of manoeuvrability, such as friction

sensation/sensitivity elements. Let us discussagainst the road surface in relation to braking

the technology related to noise, vibration andperformance. Durability, rolling resistance andride comfort developed after the war.

braking performance are essential to theoperation of the vehicle. There are also various(1) Multiplicity in the Age of Sensation andother non-essential requirements, such as noise,

Sensitivity

vibration and ride comfort. While these are not

The path from durability → manoeuvrability

as essential as durability and aspects ofperformance → sensation/sensitivity has been amanoeuvrability performance, such as running,road to diversification. A single tyre has tostopping and turning, as society has matured,fulfil various functions at the same time, whichcars have also come of age. Tyres, too, havemeans there are issues that are very difficult tobecome high-performance items with elements

resolve, since there are a number of trade-offs

of sensation and sensitivity to them now, in thethat must be both avoided and accommodated

sense of eliminating sources of discomfort.

at once. From a tyre design element perspective,

While there always was a demand for these

the necessary performances have increased,

performancefromrequirements,

they

grew

in

durability→

manoeuvrability

importance once the other more essential

performance

performance factors had been achieved.

According to this trend, there has been a shift in

In recent years there has been a growing

relative importance from material factors to

demand to remove sources of discomfort,

structural factors. This relationship is shown as

namely noise, vibration and harshness (NVH).

follows.

→

sensation/sensitivity.

There are two sides to these discomfort factors:
thenoise,

vibration

and

ride

comfortexperienced by those in the vehicle; and thediscomfort

factors(environmental

issues)inflicted on society by the running of thevehicle, such as noise in the surrounding

Targetperformance:

Dura
bility(eleme
nt)

(mate
rial)

→

Manoeuvra
bility(material/st
ructuraldesign)→Sensation/S
ensitivity(structuraldesign)environment. Technological development has
advanced on both fronts and the component
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National Museum of Nature and Science
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Since we have entered an age of seeking

improvements to both tyres and vehicles, it has

relative comfort, the sensation/sensitivity factor

resurfaced

has grown in importance. This has been

low-aspect-ratio radial tyres. The mechanisms

reflected in the amount of research from many

that produce harshness are given as follows.

angles on tyres as transmitters of vibration.

Unevenness in the road surface causes vibration.

This is the age of learning how to control theRelatively large irregularities in the roadphysicalfibre

surface, such as joins or bumps, cause a single

reinforced rubber (FRR). Various studies havestrong jolt to the vehicle, the shock of which

been carried out from that perspective with thetravels through the vehicle’s suspension andaim of reducing discomfort.

into the car body. The shock noise at this point

viscoelastic

properties

of

with

the

popularisationofhas a frequency of 200Hz or less; the problem(2) Vibration / Ride Comfort

with shocks that can be felt in the steering

While the noise, vibration and ride comfort

wheel

experienced by those in the vehicle as well as

back-and-forth vibration at 30-60Hz. This

the discomfort factors (environmental issues)evaluation is used for riding over protuberances.

inflicted on society by the running of theFig. 6.25 shows data on velocity dependence

vehicle, such as noise in the surrounding

while travelling over a protuberance. Radialenvironment, are both factors for consideration,tyres have a clear peak at 30-50km/h. The

let us examine harshness and road noise asintensity (acoustic pressure) of the noise inside

sources of noise and vibration experienced by

the vehicle coincides with the longitudinalvehicle passengers.

acceleration of the floor. This is the cause of

or

seats

is

the

low

frequency

harshness.
(i) Harshness
Since radial tyres have a large, rigid belt, they
are less able to encompass protuberances on theroad surface (enveloping power) and aresusceptible to joint shock (running over joins).
In this respect, radial tyres offer poor ride
comfort.
When travelling over uneven areas on roadsurfaces, such as joins and bumps, the shock
vibration and noise are called harshness.
Harshness was not such a significant issue
while bias tyres were the norm; it is an issue
that has accompanied the spread of radial tyres.
While

it

improvedsomewhatwith
100

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Vehicle interior noise
Unspring longitudinal
acceleration

Vibration
acceleration level

Vehicle interior
noise (μbar)

Acoustic pressurelevel

Tyre: 165SR13

Unsprung vertical acceleration

Vertical accelerationof floor (g)Velocity (km/h)
1/3 octave band centre frequency (Hz)Fig. 6.26. Vehicle Interior Noise and Unsprung
Vibration

While

Travelling

Over

a

Longitudinal accelerationof floor (g)Protuberance 2)
Velocity (km/h)

To improve harshness, the impact force must be
reduced on the tyre itself. To achieve this, thetread area must decrease in rigidity to improveenveloping and reduce the vibration from theprotuberance. Improving the longitudinal 40Hz

Velocity (km/h)

Fig. 6.25. Velocity Dependence of Acceleration(unsprung resonance fore-and-aft) and vertical

and

80Hz

Noise

Protuberance

While

Travelling

Over

a

1)

(tyre

verticalprimary)

vibrationtransmissibility is also effective. However,(protuberance height 12mm, width 25mm)

since a decrease in the rigidity of the tread area

Dotted line: radial tyre 165SR13; solid line:

means a decrease in manoeuvrability, stability,

bias tyre 6.45-13

high-speed durability and wear resistance, work
is being carried out on improving the vibration

Fig. 6.26 shows the spectra of unsprung

properties of tyre suspension so as to improvevibration and vehicle interior noise while

harshnesstravelling over a single protuberance at 40km/h.

performance factors.

whilemaintaining

these

other

The vehicle interior noise peaks near 30-40Hz
and 80-100Hz; each peak was found to(ii) Road Noise

correspond to the peaks of the unsprung

Road noise is low-frequency noise generated

vibration.

inside a vehicle when the vehicle is travellingon a rough road.
To reduce road noise, the main peaks of thepassenger

vehicle

road

noise

spectrum,

100-200Hz and around 300Hz, must be reduced.
101
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Various measures have been adopted to achieve

circumference of a circle with a diameter

this, including reducing the primary natural

approximately halfway between that of the tyrefrequency in the radial direction and increasing

and that of the wheel. Consequently, the cavity

thesecondarynaturalfrequencyoftheresonant frequency is determined by the size oftoreducevibration

the tyre and does not depend on the tyretransmissibility in the radial direction in the

structure. Recent countermeasures have been

100-300Hz range, or by reducing the vibrationconsidered, such as placing obstacles in the tyreon the tread due to unevenness in the road byso that it does not resonate.

cross-section

using softer rubber or thicker rubber.
(iv) Uniformity Vibration
Fig. 6.27 shows the improvements made by

To improve vehicle vibration and ride comfort

using these methods. However, although theseand to reduce noise, it is best if tyres are

methods improved the road noise, there werecompletely uniform on their circumference.

other effects, such as reduced manoeuvrability

Uniformity

due to reduced rigidity of the side area, ordimensions, rigidity and weight. In terms ofpoorer fuel economy due to thicker tread

tyre uniformity, the change in force during arubber; further countermeasures were needed tosingle rotation due to non-uniformity on theprevent this.

tyre axis while the tyre is travelling on a

uniformity

in

tyre

completely flat road surface is referred to as

Tyre: 185/60 R14
Vehicle velocity: 60km/h
Acoustic pressure level

means

force variation. For testing, the following are
Before improvements
After improvements

measured with a fixed distance between thetyre and the road wheel (drum) axis.
(1) Radial force variation (RFV): changes in
force

in

the

longitudinal

direction(direction of travel)(2) Lateral force variation (LFV): changes inFrequency (Hz)counterforce in the horizontal direction

Fig. 6.27. Typical Reductions in Road Noise(3) Tractive force variation (TFV): changes infrom Tyres

3)force in the fore-and-aft direction; lateralforce deviation (LFD): changes in force(iii) Cavity Resonancein the fore-and-aft direction (see Fig.

Cavity resonance is resonance from the cavity

6.28).

within the tyre. In other words, a tyre is like apipe that produces a resonant sound. The cavity
resonant frequency equates to a sound wave
frequency with a wavelength the same as the102
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(1) Radial force

A

Fourieranalysisoftheuniformity

measurements shown in Fig. 6.29 above aims
Force

to determine the higher end of the variation
waveform. The higher end is important to

One tyre revolution

analysing the causes of unpleasant noise and(2) Lateral force
Force

vibration inside the vehicle. In other words, it isFront LFD

an analysis of the source of the discomfort from

Rear LFD

One tyre revolution

vibrations.

One tyre revolution

Vibrations caused by non-uniformity of the tyre(3) Longitudinal force

are perceived as vibration or noise in the floor,
seats, steering wheel or other areas in directForcecontact with the vehicle occupants.

One tyre revolution

Fig. 6.28. Wavenumber Variations in Forces

Since uniformity manifests as the total sum ofGenerated by Tyres 4)

all the differences in tyre structure andvariations during production, it indicates abasic level of discomfort and also indicates the

One tyre revolutionlevel

RFV waveformofcompletionoftechnology

improvements. Various manufacturers haveworked on various improvements, such asFirst harmonic
Second "Third "
Fourth "Fifth "
Sixth "
Seventh "Eighth "Nineth "Tenth "

improving the degree of accuracy of factorycomponentsoradjusting

the

way

the

components adhere together, which has resulted
in a rapid improvement.
(3) Tyre NoiseFirst-tenthharmonic
composite
waveform

Let us now discuss the discomfort factors

Fig. 6.29. Sample Fourier Analysis of FV

surrounding environment.

Waveform 4)

The noise emitted directly by the tyre from the(environmental issues) inflicted on society by
the running of the vehicle, such as noise in themutual interaction between it and the road can
The measurements are shown above. Thesebe categorised two ways: noise generated while

uniformity measurements make it possible tothe vehicle is travelling straight forward (tyredetect and estimate variations in tyre structuralroad noise); and noise generated while theelements

vehicle suddenly brakes, takes off or turns

and

their

configuration

placement.

and(squeal). Tyre road noise is an issue from the103

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perspective of noise pollution, in that it is one

be tested; it was then put in neutral with theof the main contributors to vehicle exterior

engine turned off and made to coast at anoise, which is the subject of legislation. It ispredetermined speed past a microphone, which

also an issue in that it contributes to the vehicle

measured the maximum noise level.

interior noise, which compromises the comfortof the vehicle occupants. Once environmental(4) Types of Tyres and Noise

issues came to the fore in Japan, manufacturers

Causes of Tyre Noise

have put concentrated efforts into this issue, asPattern Noise

it is a serious issue for the tyre industry.

The most dominant tyre noise is pattern noise.

Japan

Manufactures

This occurs due to a pump effect, in which air

Association (JATMA) and other members oftrapped in the grooves of the tread pattern is

the Japanese tyre industry carried out months

released when the tyre rolls and that area either

and years of vital testing and research on how

loses contact with the ground or presses down

to reduce noise, from basic studies on tyre roadagainst the ground. This is a major source ofnoise generation mechanisms to investigating

noise. Altering the pitch of the pattern disperses

testing methods, ascertaining current road noise

the frequency of the generated pattern noise.

conditions and examining noise reduction

While this does not reduce the sound energy, it

technology and its impact on other performance

widely disperses the frequency of the generated

factors. JATMA summarised these findings innoise to make it less noticeable. There is a

Taiya Dōro Sōon ni Tsuite [Tyre Road Noise] 5).

relationship between the pitch of the pattern

Truck and bus tyres generate more noise thanand the speed of revolution of the tyre. The

passenger vehicle tyres. Running trucks andnoise is generated by a fundamental wave of

buses in a small country during a time ofaround 200-1000Hz and a high frequency wave.

growth, such as Japan’s period of rapid

Generally, the greater the number of grooves

economic growth, leads to major environmental(ribs) parallel to the direction of travel, theissues, particularly in high-traffic areas; thequieter the noise; the greater the number ofentire country needed a solution.

grooves (lugs/blocks) perpendicular to the

In 1973, automobile standard JASO C606-86

direction of travel, the louder the noise. Bias

“Methods for Testing Automotive Tyre Noise”

tyres are also known to be louder than radial

was enacted, standardising two methods fortyres.

testing tyre road noise: the vehicle coasting test

Truck and bus tyre patterns are shown below.

AutomobileTyremethod, in which tyre road noise was measured
using a vehicle on an actual road, and thestandalone bench test method.
For the vehicle coasting method, the vehicle
was fitted on all four wheels with the tyres to104
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(2) Rib(3) Rib-lug(4) BlockRight angle (bias)

Bias

Bias

Bias snow

Ordinary (bias)

RadialRadialRadial snow

RadialStraight rib

Noise level dB (A)(1) Lug

Radial rib
10.00 R20 14 PR (n=8)
Radial lug
10.00 R20 14 PR (n=5)
Bias rib
10.00-20 14 PR (n=3)
Radial lug
10.00-20 14 PR (n=3)

2-D/4-truck

Fig. 6.30. Typical Truck and Bus Tyre Treads 6)
Speed (km/h)

The following figure shows truck and bus noise

Fig. 6.31. Noise Levels of Various Truck andlevels. This indicates that lugs>ribs and

Bus Tyres 7)bias>radial.

(measurements taken at various places offset

Fig. 6.32 shows passenger vehicle tyre noise.

with a reference tyre) (vehicle coasting test)

These results also indicate that lugs and blocks

1800cc FR sedan

are louder than ribs, and that bias tyres are
louder than radial tyres.
buses have more individual tyres and a higher
noise level than passenger vehicles.
Accordingly, since trucks and buses are far
louder than passenger vehicles, reducing their

Noise level dB (A)As indicated in Figs. 6.31 and 6.32, trucks andRadial rib
Radial lug rib
Radial block
Bias rib
Bias snow(reference) Radial smooth

165SR13 (n=4)
165SR13 (n=5)
165SR13 (n=2)
645-13 (n=6)
645-13 (n=6)
165SR13 (n=1)

noise has become a significant issue. For thisreason, many truck and bus tyres today have a
rib pattern. This is a low-noise pattern to reduce

Speed (km/h)

noise pollution in built-up areas. It is one form

Fig. 6.32. Types of Tyres and Noise (vehicleof eliminating objectionable environmental

coasting test) 8)

elements.

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6.3.2. Summary

number of pattern design patents also related to

As discussed above, in keeping with a growing

noise. Most of the patents to do with noise anddemand to make life more comfortable, there

vibration given in the cited literature are for

was an increasing demand in post-war tyre

structural design technology 9).

technology development to remove sources ofIn terms of the relationship between vibration,

discomfort in terms of sensation and sensitivity

noise and frequency, an important task was tofactors, such as vibration and noise. Muchlevel out the average at a certain frequency toprogress has been made in this area in recent

prevent it being excessively high. This was

years as research techniques have improved.

developed further with the development of

Examination of company patent applications tocomputers. Research on the discomfort factors

ascertain the kind of tyre developments beingof noise, vibration and harshness has been anundertaken as sensation and sensitivity factors

area of technology development that has

have

that

completely matched the progress of society. It

developments in the area of noise and ride

is fair to say that it resulted in the coming of

comfort have mainly been design elements suchage of tyres.

grown

in

importancereveals

as tread design and layout. A significant

Cited references:
1) Hattori, Rokuro: Taiya no Hanashi [The Story of the Tyre], Taiseisha, June 1992, p. 76.
2) Jidōsha-yō Taiya no Kenkyū [Studies on Automobile Tyres], Yokohama Rubber Company, ed., Sankaido, April
1995, p. 197.
3) Jidōsha-yō Taiya no Kenkyū [Studies on Automobile Tyres], Yokohama Rubber Company, ed., Sankaido, April
1995, p. 195.
4) Hattori, Rokuro: Taiya no Hanashi [The Story of the Tyre], Taiseisha, June 1992, p. 82.
5) Japan Automobile Tyre Manufacturers Association: Taiya Dōro Sōon ni Tsuite [Tyre Road Noise], fourth edition,
June 1991.
6) Hattori, Rokuro: Taiya no Hanashi [The Story of the Tyre], Taiseisha, June 1992, p. 79.
7) Gomu Kōgyō Binran [Rubber Industry Handbook], fourth edition, January 1994, p. 761.
8) Gomu Kōgyō Binran [Rubber Industry Handbook], fourth edition, January 1994, p. 762.
9) For example, patent applications related to structural design for noise/vibration. Patent numbers:
Hei-05-058119 (BS) side area reinforcing layer arrangement; Hei-06-001109 (Sumitomo) optimum belt layer
configuration; Hei-06-171315 (Yokohama) combination of block and lug grooves; Hei-06-262909 (BS) shoulder
groove siping arrangement; Hei-07-061207 (Sumitomo) inner sidewall indent arrangement; Hei-07-205614 (BS)block land surface longitudinal groove control; Hei-08-337102 (BS) oriented low-gradient groove arrangement;
Hei-07-276914 (Sumitomo) vibration damping by piezoelectric material; Hei-10-086611 (BS) groove side wallbuffer wall arrangement; Hei-10-147113 (BS) indentation arrangement between side and shoulder; Hei-10-166809

106
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(Yokohama) maximum width side indentation arrangement; Hei-10-291403 (Toyo) reinforcing layer arrangement
over belt and under ribs; Hei-11-059136 (Toyo) side reinforcing layer arrangement; Hei-11-091314 (BS)arrangement of inclined grooves at an angle to the central groove; 2000-016030 (Yokohama) side area indentation
arrangement; 2000-158916 (BS) siping groove arrangement; 2000-233609 (Toyo) dynamic vibration absorberprotrusion arrangement; 2001-191743 (BS) carcass side area double-layer arrangement; 2001-239809 (BS)countermeasures against air column resonance by linking the tread cavity with the circumferential groove;
2002-019423 (BS) block arrangement design; 2003-011617 (BS) asymmetric centre block arrangement on thepress-out and press-in sides; 2003-260906 (BS) width-direction intervals in the belt layer with specific widths;
2004-351970 (BS) pitch arrangement; 2005-145429 (Sumitomo) cushion rubber arrangement between the belt andcarcass; 2006-199101 (Toyo) extending the block from the shoulder to the side; 2008-024256 (Yokohama) carcass
bead area reinforcing layer arrangement; 2009-107448 (Yokohama) double-layer shoulder carcass arrangement
Abbreviation: BS: Bridgestone; Sumitomo: Sumitomo Rubber; Yokohama: Yokohama Rubber Company; Toyo:
Toyo Rubber

6.4. The Age of Integration: the Coming ofof theories on tyre design. By establishing

Age of Radial Tyres in the Age ofmutual connections between different areas,

Integrationsuch as incorporating design elements into
durability and rolling resistance, which had

6.4.1. Advent of the Age of Theory

previously been considered as mainly involving(Theorisation for the simultaneous achievement

material design issues, these studies enabledof performance factors such as durability andnewmanoeuvrability; fuel economy, grip andbreakthroughs for existing trade-offs. Thesesensitivity; noise, vibration and ride comfort)

theories were mainly to do with the geometric

Underlying the shifting trend from durability →design of tyres with presuppositions closer

manoeuvrability→

actual running conditions, namely, filled withsensation/sensitivity has been a shift on

air and under load. In other words, the ideas

emphasis from material elements to structuralthat surfaced took into account the tension

elements. Nevertheless, techniques to achieve

distribution during use, the changing shape ofthese target outcomes have been narrow inthe tyre and other factors. In short, thesescope, with durability limited to material

theories proposed major strides in progress byfactors

using structural design elements to solve

andperformancesense/sensitivity

limitedtostructural design factors.
From

the

1980s

developments,

which

provided

performance issues that had previously been
onwards,

Japaneseviewed as falling into the material elements

manufacturers starting publishing a succession

category. Furthermore, these were also being
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published by all companies.

With the advance of globalisation, tyres had to

Structural designers expanded their scope of

become more diverse to meet a broadening

investigation

range of usage conditions. The technology also

from

their

main

areas

of

responsibility, namely, noise, vibration, ride

had

comfort, driving stability, etc. to include

multidisciplinary approach. This necessitateddurability and rolling resistance through carcass

an integration of materials and design, given

tension control.

the mutual relationship between material designThistheorisation

which

requiredaelements and structural design elements. Thisof

was an age of tyre design theory, encompassing

super-computers ushered in a drastic leap indurability and manoeuvrability performancecomplexity, combining all kinds of factors:

factors as well as all aspects of sensation andexamining what kind of materials to use andsensitivity factors. The task of finding andhow to structure them, whether or not fibrebalancing a compromise between factors

reinforced rubber could work, and determining

without sacrificing any of them was a task well

physical constants such as frequency andsuitedacoustic pressure for vibration, sound and otheradvanced computer design technology, thisfactors, particularly in the area of sensation andworked to the advantage the overall situation.

sensitivity. As these factors grew in importance,

Consequently, the level of Japanese integration

more advanced calculations were required,technology during this era was world class. The

paving the way for large-scale computers andfollowing are some of the theories by various

the finite element method.

companies.

ofcomputers.

withdiversify,thedevelopment

coincided

to

The

age

to

the

Japanese.

Combinedwith

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Rolling Contour Optimisation Theory (RCOT), Buridjisuton Nanajūgo-nen-shi [The 75-Year History ofBridgestone], p. 232
At the time, manufacturers around the world were designing tyres based on natural equilibrium shape theory. This
shape is determined mathematically under conditions in which the tension of the air pressure is applied uniformly andis thought to be the most stable shape for a tyre.
A FEM model was created in which minute differences in tyre shape were deliberately emphasised and the energy
loss predicted. The theory held that deformation could be absorbed by increasing tension to suppress deformation inareas susceptible to energy loss and reducing tension in areas not prone to energy loss. This is the main idea behind
the RCOT theory, to “distribute the necessary tension to the necessary areas.” Specifically, the theory proposed a
non-equilibrium cross-section shape to increase the tension at the bead and belt areas (optimal travelling shape

RCOT shape
Conventional shape

Carcass tension distribution(radial direction)

theory).
RCOT shape tension distribution
Conventional shape tension distribution

Belt tension distribution(circumferential direction)

RCOT shape tension distribution
Conventional shape tension distribution
RCOT Carcass Shape and Tension Distribution
Jidōsha-yō Taiya no Kiso to Jissai [Foundation and Reality of Automobile Tyres], Bridgestone Corporation,
Sankaido, p. 94.

Tension Control Optimisation Theory (TCOT), Buridjisuton Nanajūgo-nen-shi [The 75-Year History ofBridgestone], p. 233; Watanabe, Tetsuo: Taiya no O-Hanashi [The Story of the Tyre], (Japan Standards Association),p. 123.
Clarifying the tyre distortions and their occurrence mechanisms and attaining a shape to suppress those distortions by
TBR new shape design theory.
Since TCOT increases the radius of curvature of the carcass at the bead area and reduces the radius of curvature at
the top of the sides, tension increases at the bead area, which reduces deformation, thereby improving the durabilityof the bead area. This increase in tension and reduction in deformation of the bead area improves durability by 20%
and at the same time also improves rolling resistance, wear resistance, wet braking performance, driving stability andother trade-off performance factors.
Fig. 6.33. Buridjisuton Nanajūgo-nen-shi [The 75-Year History of Bridgestone], (Bridgestone Corporation, May
2008) 1) pp. 232-233

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National Museum of Nature and Science
Vol.16,2011Driver Oriented New Ultimate Tyre Science (DONUTS), Buridjisuton Nanajūgo-nen-shi [The75-Year History of Bridgestone], p. 305.
DONUTS is a technology comprising three other technologies: Grand Unified Tyre Technology(GUTT), an automated evolutionary design method; O-Bead, a bead with improved roundness; andLong Linkage (LL) carbon.
GUTT is a method of optimising target performance factors through computer simulation.
O-Bead is a shape of bead that fits the rim and tyre in a near-perfect circle, improving the straightrunning stability of the tyre. LL carbon is a new type of carbon that has an increased chain of carbon
particles to achieve both improved wear resistance and reduced rolling resistance, previously
thought to be mutually exclusive.
Advanced Quality of DONUTS (AQ DONUTS), ibid, p. 326.
Adoption of two technologies to prevent deterioration of performance due to on-going wear on thetyre, particularly when wet.
- AQ compound: use of compounding agents to suppress the hardening of the rubber- Tread in tread: Once the tyre is worn to around half, rubber appears to suppress the gradual decline
in performance, preventing the deterioration in wet performance and other performance factors.
Conventional shape belt tension

GUTT shape belt tension

Conventional shape carcass tension

Conventional shape
GUTT shape

GUTT shape carcass tension

Maximised Belt and Bead Tension Distribution using GUTT
Jidōsha-yō Taiya no Kiso to Jissai [Foundation and Reality of Automobile Tyres], Bridgestone
Corporation, Sankaido, p. 96.
Fig. 6.34. Buridjisuton Nanajūgo-nen-shi [The 75-Year History of Bridgestone], (Bridgestone
Corporation, May 2008) 2) pp. 305, 326.

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PSP-Y, (Sumitomo Gomu Hyakunen-shi [Hundred-year History of Sumitomo Rubber]), p. 376; 1996, fitted tyre sale,p. 376.
A new technology developed to address a change in required performance for truck and bus tyres from theconventional “strength to withstand heavy loads” to “mobility”, “maintenance” and “economy”.
- Adoption of particulate carbon to improve tyre life and travelling performance by strengthening the bond between
the rubber and the carbon- Flat, smooth, tread shape design to improve uneven wear resistance by suppressing dimensional changes in tyres
from travelling- Tread block layout design based on independent chaos theory to reduce noise by dispersing the noise generated by
the tyre grooves, as well as to improve uneven wear resistance- New bead structure design to improve rim insertion when fitting the tyre to the wheel and to improve air insertion
when inflating the tyre
Evolution into Dunlop Energy Control Technologies (DECTES), p. 440.
Adjusting the distribution of ground contact area to evenly distribute wear energy and prevent uneven wear resulted
in less maintenance; adopting highly active carbon in the tread rubber resulted in improved tyre life; suppressing theenergy loss incurred with each revolution of the tyre resulted in lower fuel consumption.

Digital Rolling Simulation (DRS) → Digi-Tyre, ibid, p. 382.
Analysis of a rolling tyre model, reproduced exactly from the tread pattern to the detailed tyre structure.
Four type of simulations(i) Contact shape / contact pressure simulation: “digital profile” allowing viewing of the contact surface of a tyre
while travelling at 200/h
Led to the implementation of greater driving stability at high speeds with a wide ground contact surface at highspeed.
(ii) Wear energy simulation: “digi-tyre pattern” allowing viewing of where the tyre is wearing away
Block shape enabled even wear energy across the ground contact surface of the tyre while rolling, reducing unevenwear and lengthening the life of the tyre.
(iii) Rubber compound simulation: “digi-tyre silica water-repellent rubber” enables the digi-tyre to run on any roadsurface
Proper blending of water-repellent rubber for summer, silica for wet use and particulate carbon for dry use,
improving both wet grip and tyre life.
(iv) Noise / vibration simulation: “digi-tyre chaos array” allows hearing of tyre sounds while running
An array formed with an appropriate mix of regularity and irregularity, resulting in a balance between preventing
uneven wear, which requires regularity, and reducing noise, which requires irregularity.
Fig. 6.35. Sumitomo Gomu Hyakunen-shi [Hundred-year History of Sumitomo Rubber] (Sumitomo Rubber Industries,
Ltd., December 2009) 3), p. 440, 382

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Strain Energy Minimisation Theory on Loaded Tyre (STEM), Yokohama Rubber Company
The STEM shape uses a carcass line with the tyre inflated (FEM design theory). As opposed to an
equilibrium carcass line derived from the balanced state of the membrane alone (only the belt andcarcass), STEM uses a carcass line derived from the balanced state of the rigidity distributed acrossthe entire tyre (very different from the equilibrium carcass line at the bead area). Accordingly, thissuccessfully evens out the strain energy on the bead area and the belt edge. This is an under-loadstrain energy optimisation theory with a tyre shape based on the assumption that the tyre is travelling
and the radius of curvature of the carcass line at the sidewall area is approximately the same as R
with less deformation while inflated.
New belt structure

New shoulder shape
SER (shoulder edge rib,
rib pattern)

Four new designs support
STEM

Fatigue-resistantrubber material
Straight side shape

SCL driving stability theory, ibid.
Theoretical relationship between the yaw rate and vibration of a vehicle and the cornering force on
the tyres while steering.
When the driver turns the steering wheel, a slip angle is applied to the tyres and they undergo
significant deformation, generating cornering force.
When tyres are steered out of a straight line position, the tread area does not follow the movement of
the rim immediately, but after a time lag. SCL theory holds that this feeling of delay can be made tomatch the feeling sensed by the vehicle occupants. The theory proposes the idea of matching thesensations of the driver with the movements of the vehicle. Accordingly, the SDH (side height) islowered. Society of Automotive Engineers of Japan, Conference, October 1987, p. 527.
Equilibrium shape line
SCL shape

Tyre Shape Parameters

SCL Shape

Fig. 6.36. Yokohama Rubber Company, Motor Vehicle, Vol. 38, No. 54 (STEM) 4)
Society of Automotive Engineers of Japan, Conference, October 1987 (SCL) 5)
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DSOC Theory, (published August 1988) (Tōyō Gomu Kōgyō 50-nen-shi [The 50-Year History of
Toyo Tire & Rubber], 1996), p. 241.
DSOC theory enabled analyses of stress and strain while travelling using a supercomputer. It alsoenabled analysis of the contact area while travelling. This provided instant understanding of many
performance factors that could not be known through conventional vehicle testing alone, which inturn made it possible to develop a better product in a short space of time. This resulted in the
publication (in September the same year) of DSOC-S theory, a passenger vehicle tyre arrangement
optimisation system that provided the optimal arrangements of two types of tyres with independent
patterns and structures.

DSOC-S theory

DSOC-S optimal tyre arrangement
Allows optimal vehicle tyre arrangement toimprove manoeuvrability performance(turning performance, straight-line
stability, wet running performance) for any
vehicle drive system.
N tyreP tyreDSOC-S theory

Rear-wheel drive(RD)

Front-wheel drive(FD)

Four-wheel drive(4WD)

DSOC II (Tōyō Gomu Kōgyō 50-nen-shi [The 50-Year History of Toyo Tire & Rubber], 1996), p.
288.
DSOC II focuses on the space between the tyre and the road surface, which cannot be viewed using
ordinary methods, but can be observed through computer simulation. This advanced technology
optimises tyre performance and has been applied to passenger vehicle tyres as well as truck and bus
tyres. As a further evolution of DSOC, the dynamic simulation tyre optimisation design theory,
DSOC II incorporated cross-section shape, material properties and tread pattern to produce
integrated, optimised designs.
Fig. 6.37. Tōyō Gomu Kōgyō 50-nen-shi [The 50-Year History of Toyo Tire & Rubber] (Toyo Tire &Rubber Company, March 1996), pp. 241, 288.

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Cited references:
1) Burdijisuton Nanajūgo-nen-shi [The 75-Year History of Bridgestone], Bridgestone Corporation, May 2008, p. 232.
2) Buridjisuton Nanajūgo-nen-shi [The 75-Year History of Bridgestone], Bridgestone Corporation, May 2008, pp.
305, 326.
3) Sumitomo Gomu Hyakunen-shi [Hundred-year History of Sumitomo Rubber], Sumitomo Rubber Industries, Ltd.,
December 2009, pp. 440, 382.
4) Yokohama Rubber Company, Motor Vehicle, Vol. 38, No. 54.
5) Hanada,Ryoji: Society of Automotive Engineers of Japan, Conference, October 1987, summary, p. 527.
6) Tōyō Gomu Kōgyō 50-nen-shi [The 50-Year History of Toyo Tire & Rubber], Toyo Tire & Rubber Company,
March 1996.

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7. Detailed Description of Tyres Requiring Additional Performance
The preceding chapters have systematically(weight, take-off and landing speeds), runway

discussed the ordinary properties of tyres. In

conditions, weather conditions and manner ofother words, we have outlined the history andbraking. The tread pattern is usually a rib type,systematisation

comprising four to six grooves running in theoftechnology

relatedtoperformance factors that are ordinarily required

circumferential

in tyres, such as durability, manoeuvrability,

take-offs and landings, the grooves wear away

noise and vibration. However, some tyres

and the tyre is replaced. In many cases, the tyrerequire additional, extreme performance factors.

is retreaded, with the worn tread removed andThis

new tread put on. The retreading process can bechapterdevelopment

discusses
of

tyres

the

historyrequiringof

specialdirection.

After

200-300

repeated five to six times.

performance factors, including aircraft tyres,

During landing, the tyres are subjected toconstruction vehicle tyres (high durability),

significant vertical impact at the moment of

two-wheeled vehicle tyres (structure) andcontact with the ground. Since they go from notstudless tyres (snow and ice friction).

moving during flight to suddenly rotating, theThese tyres have presented challenges to meettyres are subjected to major acceleration in thethe required performance factors.

tangential direction against the runway surface
on contact with the ground and are rubbed
vigorously. Compared to ordinary tyres, aircraft

7.1. High Demand for Durability

tyres

have

the

following

distinguishing

characteristics 9).
7.1.1.

AircraftTyres:

High

Thermal(i) Aircraft tyres have significant flexure. While

Fatigue Resistancethe flexure under static load varies between

Aircraft tyres are only required for take-off andtyre types, it is around 30% (within thelanding.

range of 23.5-40%), two to three times more

Aircraft tyres must be able to soften the impact

than automobile tyres. This helps to ease thewhen the aircraft touches down on the runway

shock

and perform sufficiently to bring the aircraft toparticularly during landing.

duringtake-offandlanding,a safe stop. Accordingly, the tyres must have a(ii) Very high loading. Since the tyre size andstructure capable of bearing sufficient load

weight are reduced as much as possible tocapacity, handling the speeds required forlighten the weight of the fuselage as much as

aircraft take-off and landing and adequately

possible, the tyres carry a very high load inwithstanding the wear from the surface of the

proportion to their size.

runway. Aircraft tyres have a fixed number of(iii)Superior high-speed performance. Since

uses, depending on the aircraft performance

aircraft reach speeds of up to around115

National Museum of Nature and Science
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400km/h during take-off and landing, tyres

tolerance and low heat build-up. Accordingly,

must be stable and safe at high speeds.

natural rubber is used for aircraft tyres. Aircraft(iv) Good cold tolerance. Tyres must be madetyres have a long history as far as tyres go,of a material that can stand temperatures ofdating back to pre-war fighter aircraft, and the-40 to -50˚C, since they are used at airports

technology has been built up from thatin cold regions and are stowed during flights

foundation. The strongest requirement is forthrough the stratosphere. Furthermore, whensafety; changes in specifications cannot belanding, the tyres are required to spin,

made quickly. Durability is also a very

despite having hardened due to the low

important area in tyre technology.

temperatures.

(See Chapter 1, Fig. 1.2 for an external view ofType of aircraft tyres include small andan aircraft tyre.)

medium tyres, or low-pressure propeller aircraft
tyres,

high-pressurejetaircrafttyres,

7.1.2. Tyres for Construction Vehicles:

newly-designed flattened tyres and helicopter

High Heat Resistancetyres, among others. There are also many

Construction vehicle tyres (OR, off-road tyres)different sizes of tyres, ranging from 56”

are tyres for scrapers, dump trucks, graders,(around 1.4m) tyres for large aircraft to 12”

loaders, wheeled bulldozers, multi-wheeled(around 30cm) tyres for small aircraft tyres.

rollers, wheeled cranes, high speed cranes andWhile both bias and radial structures exist forother construction machinery used at civil

aircraft tyres as well, the radial structure is on

engineering construction sites, mines and thethe way to becoming adopted as the main

like. These vehicles are used on a wide range ofstructure in use. However, on the whole, bias

roads, from conditions, such as gravel, stonetyres are still the main structure in use, withand mud, to good, paved, public roads. These

more than 20 layers of nylon cord to ensuremachines assist with the task of digging,safety. Given the low temperature performancecarrying, scraping and levelling earth.

factor, natural rubber is used as the rubber

Unlike truck, bus and passenger vehicle tyres,material. This is because once a fuselage is

off-road tyres generally travel on unpaved

developed, it is fitted with the same structure ofroads covered with gravel or stones rather thantyres for 20-30 years until it is retired fromon paved roads. Heavy in weight, they are also

service; there are no rapid changes made. Invery large in size, ranging from the size of

future, there will be a change to radial tyres, as

ordinary large tyres for trucks and buses to 4m

radial tyres are becoming known for their highor more in outer diameter and 7ton or more in

durability, light weight and good landing

weight. Since they have a wide range of usage

performance.

conditions, the structure, rubber material and

The high durability requirement for aircraft

patterntyres means that they must have high rupture

application. Tyre structures include both radialisdetermined

by

the

intended116
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and bias; in recent years, the radial structure

deterioration in rubber quality during the longer

has increased proportionally in use due to its

vulcanisation time required for a thicker tyre,wear resistance, cut resistance and low heat

preventing heat build-up while travelling andbuild-up. For some higher speed applications,preventing cuts in the tread from travelling onsuch as dump trucks and wheeled cranes, therough roads. (See Chapter 1, Fig. 1.2 for theradial structure has become the majority. For

external view of a construction vehicle tyre.)

the tread, there is mixed use between natural
rubber compounds for their superior wear
resistance and heat resistance and synthetic

7.2. Tyres for Specific Manoeuvres: Widerrubber compounds for their superior cut

Friction Surface

resistance. The basic performance indicators
are large tyres for travelling on poor roads and9)7.2.1. Tyres for Two-Wheeled Vehicles

thick tyres for heat resistance .

Two-wheeled vehicle tyres are generally

Construction vehicles, particularly those usedcategorisedin mines such as dump trucks, are large in size

racing/non-public road tyres.

with a high loading capacity to improve theirTwo-wheeledtransportation efficiency. These types of tyres

four-wheeled vehicle tyres while travelling in

now have to support more than twice the loadthat they turn by means of the horizontal

they did around 20 years ago and ten times

rigidity of the tyre and by means of cambermore than they did in the 1960s 10). However, if

thrust (horizontal force generated when the tyre

the tyre were to be made larger, this would

tilts while travelling). Accordingly, the tread

raise the vehicle’s centre of gravity andradius is smaller and the area that comes incompromise the stability and controllability ofcontact with the road surface extends as far as

the vehicle; therefore, the tyres have been

the tyre shoulder, so the tread pattern continues

flattened. This increase the loading rate per air

as far as this area (see Fig. 7.1). The tyrevolume without increasing the external size ofstructure is mainly radial, like passenger

the tyre. However, to achieve this required

vehicles, but bias tyres are still used for someother technology to maintain the heat resistance,roughwear resistance and cut resistance. This

motorcycles.

necessitated

Usage conditions differ between four-wheeled

technology

10)

new

structural

andmaterial

.

road

into

publicvehicle

tyres

and

road

tyres

in

tyres

and

differfromsomefamilyvehicles and two-wheeled vehicles in theDevelopment of these tyres did not simply

following two ways 8).

mean taking a truck or bus tyre and making it(i) High air pressure for a comparatively lightbigger. A lot of research had to be carried out

load, meaning a smaller ground contact area.

from many different angles to overcome aAround half the number of passenger

number of major hurdles, such as preventing

vehicles.
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(ii) High horse-power engine to generate

tread.

driving power for a comparatively small

Tyres for both good and poor road conditions

ground contact area. A high driving force on

use a block pattern, focusing on travelling

the tyres for a comparatively small groundperformance on poor road conditions. The

contact area, meaning the horse-power load

block pattern also allows for stable travel on

per unit surface area ranges from low to highgood road conditions.

depending on the make. Large motorcycle
tyres face driving conditions around twice as(2) Tyres for Racing/Non-Public Roads

rigorous as passenger vehicle tyres and(i) Competitive road racing tyres

around five times that of truck tyres.

There are three types of motorcycle racing:road racing, motocross and trials.
(ii) Distinguishing characteristics of road racingtyres
1.Flattened tyre used for the rear wheel toincrease stability at high speed. This also
prevents slipping while cornering.
2.Moderately rigid, thin tyre with a rib-type

Fig.

7.1.

Cross-Section

Diagramofa

Two-Wheeled Vehicle Tyre 11)

tread design to reduce rolling resistance athigh speed as much as possible.
3.Special wear-resistant, age-resistant tread
rubber is used to withstand high-speed
travel.
The wheels must be in perfect balance fortravelling at high speeds on paved roads.
Tyre pressure rapidly increases immediately
once travel commences. High pressure reduces

Fig. 7.2. Two-Wheeled Vehicle Tyres 12)

rolling resistance but also reduces road holding.
Starting pressure must be adjusted with care.

(1) Tyres for Public Roads

The appropriate pressure depends on the

Tyres for ordinary public roads fall into two

weather, temperature, road conditions, tyrebroad categories: tyres for good road conditions

properties, vehicle properties and other factors.

and tyres for both good and poor roadconditions. Both are considered to be suitable(iii) Distinguishing characteristics of motocrossfor use in all weather conditions. The importanttyres

factor is the arrangement of grooves in the

For races held on unpaved tracks, tyres have a118

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block design with most of the tread protruding

out of conditions in northern Japan. Developedout a long way to bite into the ground surface

as a result of dust problems caused by spiked

while running.

tyres in high-traffic snow areas, these tyres

To prevent skidding sideways, the front wheel

pioneered new areas of winter performancetyre has a more rib-like block design. The reartechnology,

wheel tyre is as thick as possible with low tyrerubber performance.

pressure so as to grip the track surface even on

While spiked tyres used on cars in northernsoft earth (by enlarging the ground contact

winters are popular due to their capacity toarea).

maintain high running stability on snow and ice,

As with other tyres mentioned above, there is adust issues in the 1980s saw local authorities

transition to radial tyres as development

and other groups actively campaigning against

continues.

them.

particularly

low-temperature

Fig. 7.3 shows the high amount of dust during
7.3. Improved Friction Performance on

winter. Prior to the prohibition on spiked tyres,

Snow and Ice

the times in which spiked tyres were usedcoincided with the dust levels. This was due to

7.3.1. Studless Tyres

the spikes on the tyres shaving away the road

Studless tyres are a category of tyre developed

surface and spreading as dust

1982

1983

1984

1985

1986

Proportion of spiked tyres fitted

Amount of dust fall

Legend(t/km2/month)

Amount of dust fall (in front of prefectural
office; removed in September 1985 due to roadrelocation)
Amount of dust fall (Kimachidori Elementary
School site; 2.3m above the ground)Amount of dust fall (Chuo 3-chome
Agricultural and Forestry Central Bank roof;
15.0m above the ground)
Proportion of spiked tyres fitted (in front ofCity Hall); vehicle baseFig. 7.3. Trends in the Amount of Dust Fall in Sendai City and Proportion of Spiked Tyres Fitted 1)
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In June 1986, arbitration was set up between
residents and the tyre industry. It was decided

Edge effectthat manufacture of spiked tyres would stop at
the end of 1990, while sales would cease at theend of March 1991. Studless tyre sales volumes
grew rapidly from around 1986, turning thetables on spiked tyre sales for passenger

Rubber friction
Snow column
shearing force

Ice chunks

Compacted snow
Slipperyby 1991.

Granular snow

accounted for 98% of passenger vehicle tyres

Compacted snow

Use of studless tyres spread so rapidly that they

New snow

vehicles.

(1) Friction on Ice and Snow

Fig. 7.4. Tyre Friction Contribution Ratios on

Studless tyre driving and braking power on

Snow and Ice (Schematic Diagram) 2)

snow and ice can be represented as the total ofsnow column shearing force FB (the shearing(2) Measures to Improve Friction

force on the snow columns formed by snow(i) Adhesion / Traction Forcepressing into the grooves on the tread pattern),

A method to increase adhesion and traction atrubber friction force FC (the friction acting on

molecular level, such as molecular binding

the road surface and the pattern surface) andbetween the surface of the snow or ice and theedge effect FD (the edges of the blocks andtread rubber. The tyre road contact surface issipes digging into the snow and ice on the roadincreased and special rubber is used. Whilesurface)thesemaking the tread rubber softer has the effect ofbraking-related shearing forces contributes

increasing the adhesion / traction force (FA), if

differently on snow and ice surfaces.

it is too soft, the blocks will be lost to

The capacity of the grooves is related to thedeformation, thereby reducing the friction force.

snow and ice shearing force at the point of

An optimum firmness is required.

in

Fig.

7.4.

Each

of

departure, while the digging friction is strongly
linked to the edge effect during rolling. If there(ii) Digging Friction

are a fixed number of edges, the water repelling

Friction force caused by the edges of the blocks

effect and digging in effect can be increased byon the tread pattern scratching or breaking thefacilitating the opening of the sipes (fineroad surface. While making the blocks smaller

grooves on the tread).

and greater in number increases the number ofedges, this also reduces the rigidity of theblocks; if the blocks undergo significant
deformation, then the ground contact area120

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reduces in size and the friction force decreases.
The optimum values are determined by the sizeof the tyre, the size of the blocks, the number ofsipes, the rigidity of the rubber and otherfactors.
(iii) Drainage / Hydrophilic Friction
Sipes working effectively can use drainage toincrease friction by removing the pseud-liquid
layer, or water film, at -5˚C to 0˚C, thereby
proving to be an effective means of improving
performance over ice. However, with frequentuse, the blocks deform too much, which has the

Fig.

7.5.

RubberContaining

opposite effect. Hydrophilia has mainly to do(Multi-Cell Compound) 3)

Bubbleswith the effect of the rubber.
Frozen road surfaces have a low friction

1) The microscopic cells produce microscopic

coefficient and are very slippery. Frictional

irregularities on the surface of the tread

heat can easily turn the pseudo-liquid layer onrubber. These provide an escape for water

the surface of the ice into a water film, which

generated through continuous slipping andacts as a lubricant.

also prevent microscopic water film fromoccurring between sipes.
2) These microscopic irregularities scratch the(iv) Use of Special Rubber
Multi-cellcompoundsarespecial rubbercompounds with large numbers of cells. These

ice and thereby improve the digging friction
FD.

microscopic closed cells are combined with

3) The microscopic bubbles reduce the rigidity

microscopic air bubbles as shown in Fig. 7.5 toof the rubber, meaning it does not lose its

produce optimum tyre performance. Theseelasticity even at low temperatures (→compounds have the following distinguishing

improved adhesion friction FA due tocharacteristics.

increased ground contact surface).
4) New bubbles appear even as the tyre starts towear, thereby enabling continuation of theaforementioned effects 1) and 2).
(v) Special Arrangements for Microscopic
Drainage
While using soft rubber is good for improving
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traction, removing the thin water film between
the rubber and the road surface is also effective.
Having microscopic asperities on the surface ofthe rubber makes this more effective. For
example, if we were to measure the friction on
ice after rubbing the rubber with sandpaper, we
would find that the coarser the sandpaper used,

Fig. 7.7. Rubber Surface Containing Shortthe greater the friction on the ice. This is

Fibres and Bubbles 4)

because the microscopic protrusions penetrate
the surface film on the ice, enabling direct

While adding bubbles and short fibres creates

contact with the surface of the ice. Conversely,

an asperity effect that drains water, the fibres

it is also thought to remove the water.

can also prevent the blocks collapsing if the

The use of foamed rubber is one means ofrubber is too soft. This means that evenensuring asperities on the surface. This has also

relatively soft blocks can have improved

shown to be effective in tyres.

friction on ice 6).

Short fibres are added to prevent deformation

Compounds with additives such as groundof the tread blocks (see Fig. 7.7); these are

walnut shells (microbit compounds) have also

placed along the blocks to reinforce them. This

shown to be effective (see Fig. 7.8). In any case,reinforcing phenomenon is shown in Fig. 7.6.

surface asperities are thought to ensure

Friction on Ice

Short fibre
reinforcing

Ordinary
rubber

Ice braking performancedrainage.

Optimum

Microbit compounds
SpikesConventional compounds

Tread rubber temperature (@-5˚C)Fig. 7.6. Short Fibre Reinforcing Effect on

Fig. 7.8. Microbit Compound Effect 5)

Friction on Ice 4)
The use of glass fibre is another example ofusing fibres in the rubber to harden it. Mixing
in glass fibres, which are softer than asphalt but
harder than ice, with the adhesive creates a“scratching effect”, which improves the friction
against the ice 7).
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(vi) Rubber Properties and Adhesion Friction

becomes softer than at peak position and theForcecontact area reduces due to collapsing from

As previously mentioned, adhesion friction

contact pressure. Conversely, the harder theforce is a primary cause of molecular-level

rubber, the better the contact and the higher theadhesion, such as molecular bonding between

friction force. Accordingly, the softness of theicy or snowy road surfaces and tread rubber.

rubber contributes to the total friction force.

Increasing this adhesion requires the rubber to

The softness of the rubber is balanced between

precisely follow the microscopic irregularities

providing friction and avoiding collapse. Inon the surface of the road to enable goodother words, truck and bus tyres, which havemicroscopic contact between the rubber and thehigh contact pressure, must be harder thanroad surface. Accordingly, it is important thatpassenger vehicle tyres, which have lower

the rubber is elastic at low temperatures, suchcontact pressure.

using rubber that remains as soft as possible at
low temperatures. To ensure softness at low
temperatures,polymers

withaμ on ice

as on icy surfaces; this is usually achieved byContact
pressure

Testing equipment:straight friction tester
Sample shape:

lowglass-transition temperature (Tg) (such as

Tyre
blocksGood
Road surface

natural rubber or butadiene rubber) are used,
Rubber hardness Hs (0˚C)

while use of low-temperature plasticisers
ensures the rubber does not harden at theFig. 7.9. Relationship between Tyre Blocktemperature of use.

Rubber Properties and μ on Ice 4)1) Interaction between Rubber Hardness andTread Block Hardness(vii) Friction by Pattern

Block size, number of sipes and rubber

1) Removal of Water Filmhardness work together to create optimum

Arrangements of fine grooves such as siping

values for performance on ice.

are another basic design method for studlessFig. 7.9 shows the relationship between rubber

tyres.

properties and coefficient of friction μ on ice.

The block sipe edge effect in the pattern is

For this experiment, the μ on ice taken to shifteffective for increasing the digging friction andone block sideways was measured. As thebreaking the water film occurring between the

figure shows, when the surface pressure on theroad surface and the tyre surface.

rubber block varied, it peaked against the

As shown in Fig. 7.10, the friction force

hardness at all levels of surface pressure. The

increases as the number of pitches and sipes onhigher the surface pressure at the peak location,

the tyre circumference increases to create thethe further the shift in the direction of hardness.

edge effect. This is because the fewer the

In other words, when the block is shifted, it

pitches, the longer the blocks become and the123

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longer the area that comes into contact with thearea. The same can be said of the number ofsipes. However, each arrangement has a peakfriction force; having too many pitches or sipes
reduces the block rigidity, which results inblock collapse and leads to a reduction in actual
ground contact area.
While studless tyres can be said to be an item

Braking friction coefficient on ice

water film occurring in the road surface contact

Tyre size: 185/70R13
Load: 360 kg
Internal pressure: 1.9 kgf/cm2
Rim: 5J
Ice temperature: -2°C
Number of pitches on thecircumferenceof Japanese technology born out of Japaneseconditions, the main developments in Japan

Number of sipes / per block

have been to do with developing tread rubber

Fig. 7.10. Braking on Ice and the Edge Effect 3)

and tread patterns.
The following three developments in tread

In terms of pattern design, patterns have tended

rubber are worth noting.

to use the scratching effect at the pattern edge

- Use of soft rubber to fit against the surface ofand reinforce blocks that have been softened by

the snow or ice

using soft rubber.

- Adding combined materials to scratch thesurface of the snow or ice and improve the(8) Summary

friction

The above developments came about in- Arranging cavities such as bubbles to remove

response to the environmental issue of dust.

the water from the boundary layer occurring on

These started out for the Japanese market, but

the surface of the snow or ice

have since built up a strong position andcurrently have a major market. As mentioned
above, these are still being researched by tyrecompanies,

withfurther

performance

improvements expected.
(See Chapter 1, Fig. 1.2 for an external view ofa studless tyre.)

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Cited references:1) Supaiku Taiya Funjin Hassei Bōshi-hō [Methods to Prevent Dust from Spiked Tyres], Sendai Bar Association,
February 1991, p. 13.
2) Gomu Kōgyō Binran [Rubber Industry Handbook], fourth edition, The Society of Rubber Science and Technology,
Japan, ed., January 1994, p. 754.
3) “Sutaddoresu Taiya no Kaihatsu (Jōyōsha Taiya) [Development of Studless Tyres (Passenger Vehicle Tyres)]”,Sakamoto, Takao; Hirata, Yasushi: Journal of The Society of Rubber Science and Technology, Japan, Vol. 65, p.
713, 1992.
4) “Sutaddoresu Taiya no Kaihatsu (Torakku oyobi Basu-yō Taiya) [Development of Studless Tyres (Truck and Bus
Tyres)]”, Tomoda, Hajime; Ishikawa, Yasuhiro: Journal of The Society of Rubber Science and Technology, Japan,
Vol. 65, p. 721, 1992.
5) Kawano, Tatsuya; Ueyama, Hiroaki: Journal of The Society of Rubber Science and Technology, Japan, Vol. 69, p.
763, 1996.
6) Ishikawa, Yasuhiro: Journal of The Society of Rubber Science and Technology, Japan, Vol. 70, p. 198, 1997.
7) Sumitomo Gomu Hyakunen-shi [Hundred-year History of Sumitomo Rubber], Sumitomo Rubber Industries, Ltd.,
December 2009, p. 386.
8) Jidōsha-yō Taiya no Kenkyū [Studies on Automobile Tyres], Yokohama Rubber Company, ed., April 1995, p. 47.
9) Jidōsha-yō Taiya no Kenkyū [Studies on Automobile Tyres], Yokohama Rubber Company, ed., April 1995, pp.
56-58.
10) Based on Fig. 2-7-3, Jidōsha-yō Taiya no Kiso to Jissai [Foundation and Reality of Automobile Tyres],
Bridgestone Corporation, Sankaido, 2006, p. 53.
11) Gomu Kōgyō Binran [Rubber Industry Handbook], fourth edition, January 1994, p. 772.
12) Jidōsha-yō Taiya no Kiso to Jissai [Foundation and Reality of Automobile Tyres], Bridgestone Corporation,
Sankaido, 2006, p. 44.

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8. Summary of Technology ProgressFig. 8.1 shows the progress of the technology.

Following the post-war introduction of new

Tyre

broad

materials (nylon, SBR), the transition to radialcategories: “seeds”, or product ideas from tyre

tyres began around 1970. During the oil crises,

companies to provide technology and develop

work reached a global scale on technology to

products; and “needs”, or demands placed on

avoid the trade-off between wet μ (grip on wet

tyre companies by society for products inroad surfaces) and LRR (low rolling resistance).

response to issues that arise. Fig. 8.1 shows that

Later, once the work on low fuel consumption

while the major trends have varied for bothas a result of the oil crises eased off, tyre“seeds” and “needs”, up until around the year

manufacturers turned their attention to high tyre

2000, “needs” and “seeds” products were

performance (flattening). In the 1990s, newappearing in an almost alternate progression.

global environmental issues arose, ushering in“Seeds” products also tended to relate toan age of “needs”, with very high levels of

structural elements, while “needs” tended todemandrelateultra-lightweight tyres, studless tyres andtechnology

toismaterial

dividedelements;

intoaccordingly,forultra-low

fuelconsumption,

structure and materials appeared in alternate

safety.

progression.

High performance tyres (HPT, high grip tyres)and flattened tyres were recognised to be in a

8.1. Seeds and Needs in Tyre Development

distinct category from fuel-efficient tyres (wetμ / LRR) in terms of grip and friction. However,Newmaterials:

Transition

Wet

there was a very high demand for technology

nylon,

to radial

μ/LRR

that could avoid a trade-off, providing bothSBR(seeds /(needs /

highperformanceandultra-low

fuel(needs /structural

material

consumption, as well as being lightweight.

material

elements)

elements)

As time progressed on from the 2000s to thepresent day, there came a turning point in theelements)

Lightweight /transition from HPT (“seeds”) to lightweight

HPT A/S

fuel economy

and

High

(CAFE: US fuelDevelopment issues such as uniformity, noise

performance

consumption

and driving ability, which were both “needs”

standards)

and “seeds”. Fulfilling all of these criteria at(seeds /Studlessonce was a major hurdle. This was an era ofstructural(needs /significant additional required performances;elements)

material

this required technology that could integrateelements)

both materials and structure.

Flattening



fuel

economy(major“needs”).

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This age of major needs required a balancevarious Japanese tyre manufacturers from thebetween multiple performance factors at once.

1980s onwards proved to be beneficial in

The design theories that had been proposed byproviding a way forward.

Transitions in Tyre. “Needs” and “Seeds”
Durability

Manoeuvrability

Impact of technology

Wet grip / fueleconomySensation/sensitivity

Fuel economy /lightweight /studless

Needs(material
elements)

CAFE (US fuelconsumption
standards)
High performance
Halogenated (HPT) / all-season
Transition to butyl liners
Noise and driving
radialstability
Seeds
Tubeless tyres
Uniformity
Flattening(structuralelements)

Major needs era(environment)
Ultra-low R&D on newmaterials
fuelconsumption
Ultra-long-life
Safety Ultra-low
tan δ HighRun-flat
durability
High ageresistanceNo-puncture
tyresIntelligent tyres(Year)

Fig. 8.1. Trends in Tyre Technology 1)

Tyre Technology Development by Scale
Carbon indispersed state
Molecular modification
technology

Carbonconcatenation

Tyre diameter
Material
properties
Block pattern

Molecular
control

Macro control

Fig. 8.2. Tyre Technology Development by Scale 2)
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8.2. Future Integration Methods

The Gomu / Erasutomā to Mirai no Kōtsū[Rubbers/

Elastomers

andFutureFor future methods of integration, initiatives

Transportation] Rubber Technology Forumare being carried out as shown in Fig. 8.2.

tyre team gave the following prediction ofThis is the idea of tyre technology development

future tyre performance, shown in Fig. 8.3. The

by scale. From the micro perspective, tyreteam predicted that by 2030, both wet μ andstructure fits into the nano-world of molecularrolling resistance will be around 40% better

reaction control, while the world of tyre surface

than they were in 1980.

tread design is a world of centimetres, and theworld of rolling resistance – repeated loading

Progress in Tyre Performance
T. Haraguchi Toyota at IRC 2005
2030 extrapolated from published dataand non-loading due to rotation – is a world of
metres. In other words, tyre performance ranges
in scope from nano-order phenomena to metres.
How all of these factors are controlled, frommolecular order to metre-level order, affects
tyre performance. The way these parameters
are calculated and incorporated will become amajor aspect of performance competition.
Many Japanese tyre manufacturers are basing

Fig. 8.3. Predicted Future Tyre Performance 3)

their designs on these ideas and are working
effectively in the environmental age.

There is a sense that current tyre technology

In this technological environment, the question

has been largely established as culmination ofremains as to how to balance the many

post-war technologies.

demands placed on tyres, many of themHardlymutually exclusive; however, progress has beendevelopments in this technology have comemade on laying a foundation. This has beenfrom Japan, although Japan has mastered andmade possible by the large number of

optimised technology invented overseas to an

automobile manufacturers in Japan, as well as

advanced level. However, Japan has certainly

the large number of tyre manufacturers. This

reached a high level of tyre technology,

has meant that tyre manufacturers have had tomastering many technologies, balancing themcompete with each other to achieve the various

and taking them to new levels, for example, a

improved performances demanded by many

very high level of advancement is evident in theautomobile manufacturers, discovering andtyrecarrying out ways to fulfil these desired

manufacturers.

performance factors. Tyre theories were one

While there is currently a sense of plateauing inresult of this adaptability.

technology, when we enter a new growthanytheoriesofthepublishedground-breaking

byvarioustyre

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period, the challenge for the next generationembryonic form, some driving force will bewill be how to implement uniquely-Japaneserequired to develop it.

technology. While this can be seen in

Cited references:
1) Gomu / Erasutomā to Mirai no Kōtsū [Rubbers / Elastomers and Future Transportation], The Society of Rubber
Science and Technology, Japan Rubber Technology Forum, 30 March 2010, p. 82; a little added.
2) Gomu / Erasutomā to Mirai no Kōtsū [Rubbers / Elastomers and Future Transportation], The Society of Rubber
Science and Technology, Japan Rubber Technology Forum, March 2010, p. 75.
3) Gomu / Erasutomā to Mirai no Kōtsū [Rubbers / Elastomers and Future Transportation], The Society of Rubber
Science and Technology, Japan Rubber Technology Forum, March 2010, p. 81.

1970
Meiji
Taisho Showa
Post-War(→ transition to radial) Heisei
Start of the tyre
Start of the age ofMatuarisation of the age of motorisation
Dawn
industry
motorisation
Compounding
Period of introducing new
From bias tyres
Start of theStage of maturity oftechniques; theto radial tyres
materials
start ofdomestic tyreradial tyres
vulcanisationindustry
technology
Spread of highways(post-war)

Social changes

Durability

Required performanceYear

Environmental
measures
Manoeuvrability Quietness
SafetyLow fuel consumption
Dust pollution
Noise/vibration/ high friction

Wear resistance

Pneumatic tyres

Tyre
Fabric tyres 
structure(1913)

Cord tyres(Palmer type) (1920)

Radial tyres

Bias tyres

Studless tyres

Tubeless tyres

Run-flat tyres
Tread pattern design

Flattening(Rubber)Tackifiers

NaturalrubberMaterials(Reinforcing agents)
Use of carbon black

Synthetic rubber

High cis BR
Modified S-SBR

Halogenated butyl rubber

Use of silica(Cord)

Rayon Nylon (1955)
Fabric Tyre cord  Cotton
Rubber compound
Processing Start of
RFL adhesive
vulcanisation vulcanisation control(Inorganic accelerators, organic
technology
accelerators, c. 1920)
Mixer (Banbury)
Manufacturing
Extrudingequipment
Rolled rubber/ Rayon
Nylon Moulding machine
Vulcaniser

Steel cord / polyester
Brass adhesive (1970-)

Bias

Steel cord / polyester
RadialBias specifications

Intermeshing mixer

Radial specifications

Fig. 8.4. Flow Diagram of Tyre Technology

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Changes in Industry Structure due toInnovations in Tyre Technology

Noise/vibration
Continuous change

Function / performance

Shift in type of business due todiscontinuous change
Technology innovation due tochange in tyre structure+ production facilities andequipment technology innovation
Use of steel cord, polyester
Continuous change
Dawn

Pre-war tyre structure innovations

Vulcanisation Compounding
technology

Age ofaccelerators

Silica technology

Flattening
S-SBR for low fuelAdhesive consumption
issuesTransition to radial

New materials
Nylon, synthetic
rubberHigh
performance
level

Low
performance
level

Bias
Both products andfacilities
disappeared
Disappearance ofcotton/rayon
Year

Fig. 8.5. Changes in Industry Structure due to Innovations in Tyre Technology

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(Appendix) Tyre Technology Timeline
Overall trends; little epoch-making technology from Japan, implemented around 1-10 years behind
the West.
Text in bold represents Japanese technology; underlined text represents epoch-making technology.
Tyre RelatedMaterial Related

1769 Steel disc tyre used on Cugnot steam car

1839 Goodyear discovers vulcanisation

wheel (France)

phenomenon (USA)1835 Solid tyre invented
1842 Hancock solid tyre commercialised (UK)1843 Hancock obtains patent for vulcanisation(UK)

1845 Thomson obtains pneumatic tyre patent(UK)
1863 Michelin established (France)
1871 Macintosh patents hollow solid tyre (UK)
Continental-Gummi established (Germany)
1872 Pirelli established (Italy)1886 Tsuchiya Rubber Factory established,Japan’s first rubber company
1888 J.B. Dunlop obtains pneumatic tyre patent(UK)
Dunlop’s patent commercialised (UK)Michelin clincher tyre produced (France)
1890 Hartlet clincher tyre patented
Goodrich produces the first American tyre
(USA)
1892 United States Rubber (later Uniroyal)established (USA)1893 Solid tyres used on Daimler automobile(Germany)
B.F. Goodrich automobile tyre prototype (using
tyre fabric) (USA)1896 Dunlop Holdings established (UK)1900 Firestone established (USA)1902 Appearance of tyres with tread pattern131
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Vol.16,2011

(USA)

1904 Reinforcing effect of carbon black

Meiji Rubber produces Japan’s first

discovered

automobile tyre1904 Bead wire straight side tyre (USA)1905 Oenschlager (USA) discovers organic
vulcanisation accelerators

1908 Palmer-type tyre patented (USA)1909 Dunlop Rubber (Far East) established in
Kobe (now Sumitomo Rubber)1910 Appearance of Goodrich cord-type tyre

1912 Carbon black used as rubber reinforcing(USA)agent (USA)1912 B.F. Goodrich established (USA)1913 Dunlop (Far East) produces the first
domestically-produced tyre
1915 Use of woven cord by J.F. Palmer
1917 Yokohama Rubber founded1916 First Banbury mixer prototype (USA)1918 Appearance of pneumatic truck tyres(USA)
1920 Pirelli produces cord tyres (Italy)

1924 Discovery of anti-ageing agents

1921 Yokohama Rubber produces Japan’s

1926 Toyobo produces Japan’s first tyre cord

first cord tyre
1923 Low-pressure tyre (balloon) developed(18-30psi vs 20-55psi)
1928 Motorcycle tyres standardised in the USA
1929 Michelin railcar tyre prototype (France)
1930 Bridgestone produces Japan’s first tyreusing domestic technology (by Nihon Tabi)
1931 Bridgestone established1930 DuPont succeeds in commercialising

Michelin railcar tyre announced (France)synthetic rubber

1932 Agricultural and construction machinery
tyres standardised in the USA
1934 Michelin commences research on the1935 Synthetic rubbers Buna S and Buna N

application of steel cord for truck tyres (France)

produced (Germany)
Carothers invents Nylon 66

1937 Michelin announces steel cord tyre (bias)

1936 Japanese companies produce rayon tyre132

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(France)

prototype1938 Reinforced rayon tyre appears in the USA

1939 Schlank invents Nylon 61940 Butyl tube prototyping begins (USA)1939 RFL adhesion discovered (USA)1942 Military nylon tyre prototype (USA)1940 Butyl rubber (IIR) announced (USA)1941 Synthetic rubber GR-S production expands

1943 Toyo Tire & Rubber established1944 Dai-Nippon Aircraft Tyres (later Ohtsu
Tire and Rubber) established1946 Steel radial tyre patented and productioncommences (France)
1947 Tubeless tyre invented (USA)1948 Michelin enters commercial radial tyre
production (France)
1949 Nitto Tyres (later Ryoto Tyres) founded1950 Use of SBR begins in JapanUse of reinforced rayon cord begins
Oil-extended SBR commercialised (USA)
Nippon Zeon founded1951 Pirelli releases a radial tyre (Italy)

1952 Ziegler catalyst invented (Germany)First rayon tyre produced in Japan

1954 IR (polyisoprene) successfully synthesised(USA)

1955 Tubeless tyres adopted on new1955 BR (polybutadiene) synthesis announced

automobiles (USA)(USA)

Tubeless tyre production starts in JapanFirst use of nylon cord

1956 Use of snow tyres spreads in Europe
1958 Nylon tyres produced
Snow tyres appear in Japan

1957 Japan Synthetic Rubber founded1960 Radial tyre prototype (Japan)

1958 Japan’s first synthetic rubber

Snow tyre production begins (Japan)

successfully commercialised
1960 Halogenated butyl rubber appears (USA)1962 Polyester tyre cord becomes the norm

1962 Polyester cord becomes popular (USA)(USA)

Successful polyester fibre production

Steel cord tyre produced (Japan)
1963 First exports by Bridgestone to Malaysia
and Singapore (later withdrawn)
1964 Flattened tyre (LSH70 %) first used (USA)133
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Spiked tyre produced (Japan)
Okamoto Riken enters the tyre business
Belted bias tyres appear around this time (USA)1966 Polyester tyres fitted to new vehicles(USA)
1967 Polyester tyres fitted to new vehicles

1967 Fibreglass cord first used (USA)(Japan)1968 FMVSS come into force (also related totyres) (USA)
Belted bias tyres produced (USA)Radial tyres fitted to new vehicles (Japan)
1969 Belted bias tyres produced (Japan)
1970 Steel radial tyres produced (Japan)
1972 JATMA “Automotive Tyre Safety

1972 Aramid cord used in tyres (USA)Standards” issued (Japan)
1973 TGS (safety tyre) prototype (Japan)
1975 ECE30 safety standards start (Europe)
Puncture sealing tyres produced (Japan)
1977 Obsolete tyre grinding facility
completed (Japan)
Japan joins ISO and starts being active
1978 Use of obsolete tyres as fuel for cementkilns (Japan)
JIS standard D4320 incorporates safety
standards such as dynamic tyre testing
Fuel efficient tyres (1979 energy crisis)
HPT tyres1983 Run-flat tyres
1986 Studless tyres increase in sales
End of 1990 Spiked tyre production ceases;
sales cease at the end of March 1991
1980s-1990s Japanese companies publish tyretheories
Early 1990s Michelin announced green tyres
Since these contained silica, silica began to be

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Vol.16,2011

used around the world, particularly in passenger
vehicles; progress was also made on related
processing technology.
2000- Popularisation of run-flat tyres(side-reinforced)

Cited references for the table above:

The above table was created using references from the following sources, among others.
- Hattori, Rokuro: Taiya no Hanashi [The Story of the Tyre], Taiseisha, June 1992, pp.
229-233.
- Jidōsha Taiya no Kenkyū [Studies on Automobile Tyres], Yokohama Rubber
Company, ed., Sankaido, April 1995, p. 4.
- Buridjisuton Nanajūgo-nen-shi [The 75-Year History of Bridgestone], Bridgestone
Corporation, May 2008.
- Sumitomo Gomu Hyakunen-shi [Hundred-year History of Sumitomo Rubber],
Sumitomo Rubber Industries, Ltd., December 2009.
- Tōyō Gomu Kōgyō Gojūnen-shi [The Fifty-Year History of Toyo Rubber], Toyo Tire
& Rubber, 21 March 1996.
- 80 Shūnen Kinen We Tokubetsu-gō [80-Year Anniversary We Special Edition],
Yokohama Rubber Company, 13 October 1997.
Acknowledgements:
The author expresses sincere gratitude for the wealth of technical information and advice received
from the following persons during the writing of this Systematic Review of Tyre Technology report.
Toyota Automobile Museum

Takahiko Sugiura, Kiyoshi Koshimizu

Nichias Corporation

Hitoshi Yamada

JATMA

Takehito Kondo

Bridgestone Corporation

Yasushi Hirata, Keizo Akutagawa, Yuta Mizuno

BRIDGESTONE TODAY

Isao Ito

Rubber and Tyre Museum
Sumitomo Rubber Industries

Kosaburo Nasaseko, Yasushi Niimura

Toyo Tire & Rubber Company

Kenji Komamizu, Yukinori Morikawa

Yokohama Rubber Company

Toshihiko Suzuki, Hideo Kai, Kiyomi Ishikawa,
Masataka Koishi

Yokohama Technical Research team

135
National Museum of Nature and Science
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List of Candidates for Registration
No.

Name

FormatLocation

Manufacturer

Year

Reason for Selection
The Dunlop Rubber Co. (Far East), Ltd. started production

1of automotive tyres in 1913. At this time, 25-26 tyres were

The first

Sumitomo

domestically

RubberDunlop (Far

Industries

East)

produced

Conserved

automobile tyre

produced in Japan and were very hand-made in nature.
1913

These “fabric tyres” or “canvas tyres” were produced byoverlapping cotton fabric. The first domestically produced

Chuo-ku, Kobe

automotive tyres are a valuable piece of technology
heritage.
A Zero fighter tyre made during World War II. It was fitted

Main landing

Yokohama

gear tyre used2

on a Type-0
fighter for theConserved

Imperial

to a fighter plane found in Guam in 1963. The aircraft was

RubberYokohama

Company

RubberHiratsuka,

Company

no longer distinguishable, but the tyre was still in useable
May 1943

Wartime tyre technology developed for the military and was

Kanagawa

Japanese Navy

condition. It is still preserved in that state to this day.
very high performance, as can be seen. The size is
6.00-17.5.
Valuable as a highly durable product used on a fighter

3‘Falcon’ fighter
tyre

Bridgestone
Conserved

Today
Kodaira, Tokyo

aircraft during the war. Japanese wartime tyre technology is
Nippon Tyre

February

thought to have reached quite an advanced level using only

Company

1944

Japanese technology. This tyre was made in 1944 and was
fitted to a ‘Falcon’ fighter. Even in its current state it
appears to have hardly deteriorated. The size is 5.70-19.

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National Museum of Nature and Science
Systematic Examination of Technology Report, Vol. 16
March 31, 2011
Editor: National Museum of Nature and Science (Independent Administrative
Institution)
Center of the History of Japanese Industrial Technology(Under charge of: coordinating editor: Takayuki Nagata; editor: Toshihiko Okura;
English version: Osamu Kamei)
Publisher: National Museum of Nature and Science (Independent Administrative
Institution)
7-20 Ueno Park, Taito-ku, Tokyo 110-8718
Tel: 03-3822-0111
Japanese issue; Design and Printing: J.Spark Co., Ltd.

137
National Museum of Nature and Science
Vol.16,2011