Special Feature Article
Accelerating tire innovation-Electrification and environmental issues are increasingly being addressedTires are the only security component of a vehicle’s components that are in contact withthe road surface and have a significant impact on safety and comfort. Rubber pneumatic
tires were invented in the late 1800s. Since then, tire manufacturers have worked harddiligently to improve. The grip and comfort performance of tires in response to roadconditions. In recent years, new technologies have been developed that break withconventional concepts, and are on the verge of practical application. This report details
into the latest development trends, future possibilities and the challenges faced.
Over 100 years of working to reconcile the ‘antinomy’Tires are a major factor in the driving performance of vehicles. Although their black, roundappearance has remained unchanged over the years, they have constantly evolved.
Their development can be described as a history of balancing two opposing
performances. For example, in recent years there has been a demand for low rolling
resistance products with low energy loss, but these are generally at odds with the grip on
the road surface. The Japan Automobile Tire Manufacturers Association, Inc. (JATMA)
allows products with a certain level of compatibility between ‘rolling resistance
performance’ and ‘wet grip performance’, which are evaluated by grade, to be labelled andsold as ‘fuel-efficient tires’. It requires that the tires not only contribute to improving the fuelefficiency of vehicles, but also ensure safety.
In addition, tires have various conflicting performance requirements, such as quietness
and abrasion resistance, which have been a source of concern for engineers at various
manufacturers. While studying rubber at the molecular level, the required performance has
been improved by kneading in various raw materials, such as carbon black, which
increases strength, and silica, which improves performance on wet roads. The patternshape of the ground surface is also being optimized to suit the application.
Performance standards forced to accommodate electrically powered vehicles
Looking at the global automobile market, SUVs, which have larger bodies than sedans
and coupes, have become more popular in recent years. In addition, EVs are also gaining
market share, but both have one thing in common: they are heavy vehicles.
Brakes are being increased in diameter to cope with the increase in vehicle weight, buttire size cannot be increased to an extreme degree.
Therefore, it is necessary to use tires with a low flatness ratio and reduced side height
without changing the outer diameter, in order to cope with the increased vehicle weight.
This requires a more robust internal structure and requires advanced manufacturing
technology.

The manufacturers position high-performance passenger car tires of 18 inch and aboveas ‘premium tires’. They pay attention to the shape of the ground contact surface and thecomposition of raw materials, and work to add value by, for example, improving quietness
and grip. By increasing the sales ratio of these higher-priced products, manufacturers arealso working to improve their profit margins.
Bridgestone Corporation, for example, has named its lightweight, highly rounded tire
design foundation technology ‘ENLITEN’ and is rolling it out in new products. While raising
the level of performance, they intends to differentiate itself in the global market byintroducing products that highlight specific performance characteristics, such as grip andquietness, to capture the needs of users.
Tires that change their characteristics depending on the situation
Recently, efforts have been made to develop new technologies that overturnconventional wisdom, such as changing the properties of rubber.
‘ACTIVE TREAD’ technology, which Sumitomo Rubber Industries, Ltd. will introduce ’tothe market this autumn, is an unprecedented technology that changes its performance inresponse to road conditions. It changes the properties of the rubber in response to roadsurface moisture and the temperature environment to reduce the loss of grip. It wasachieved by combining several materials provided by chemical manufacturers andresearch institutes.
Tires currently on sale can be broadly divided into two main categories, ‘summer tires’and ‘winter tires’, but the actual driving environment changes from moment to moment,from dry roads to puddles, on snow and ice. If tires can change their characteristics to suitroad conditions, this will lead to greater safety and comfort. This can be particularly
effective in reducing non-operating time for tire changes in taxis and rental cars, which arerequired to drive in all weather conditions.
They intend to use the technology for all-season tires first, and then gradually expand it to
EVs and other applications. Although there are still issues to be addressed, such as thesupply of raw materials, the accuracy of performance changes and the application of thetechnology to large-diameter trucks and buses, they intends to continue development of
this new technology, which has the potential to make winter tires, so-called studdles tires,
unnecessary.
No air and no punctures
Manufacturers are also aiming to realize ‘Puncture-free tires’. ‘Run flat tires’, which havereinforced sidewalls and can be driven on even when deflated, are already commerciallyavailable, but efforts are also being made to develop ‘Airless tires’ that are not inflated.
Airless tires do not have sidewalls with the manufacturer’s name and size printed on themand have specially shaped spokes on the inside to absorb impact. In commercial vehicles,
this can reduce efficiency and cost increases due to punctures, and also has theadvantage of reducing maintenance such as air pressure checks. If ‘Retreading’, in which
the ground surface is replaced, is realized in the future, costs and raw materials can also
be reduced.
Similar concepts are being studied by four Japanese manufacturers, as well as
MICHELIN and The Goodyear Tire & Rubber Company, although the tire structure itself
would need to be significantly changed. MICHELIN has already teamed up with transport
operators in France and Singapore to demonstrate delivery by vehicles fitted with airlesstires.
On the other hand, legislation is an issue in Japan. Under the Road Trucking Vehicle Law,
airless tires have not yet been approved for use on public roads. Domestic companies
have been developing them since the mid-2000s, but have only considered using them
mainly on golf carts and small EVs that run on private property.
In March this year, Bridgestone Corporation began demonstration tests on public roads
after consulting with Ministry of Land, Infrastructure, Transport and Tourism on legal
compliance. It is hoped that their efforts will lead to a move towards driving on public roadsin Japan.
Tires act like suspension‘I wish the hardness of the tire would change when going over bumps’. This simple
thought of an engineer led The Yokohama Rubber Co., Ltd. To make a technological
proposal for future tires at last year’s ‘JAPAN MOBILITY SHOW 2023’.
‘Future Sport Tire concept’, which was unveiled for the first time, incorporates ‘Variable
Hardness Stabilizer’, a mesh-like structure, inside the tire. It is made of a special material
that changes its hardness when electricity is passed through it, enabling the rigidity of thetire to be varied. The tire characteristics can be adjusted to suit the driving situation, suchas on a circuit or in town. Assuming automatic driving, the system can also be used tochange tire hardness in response to bumps or sunken road surfaces detected by on-board
cameras and sensors, and to raise the vehicle height on one side at the moment of a sidecollision to prepare for the impact.
Currently it is still in the planning stage, but they have received positive feedback on theidea from car manufacturers and manufacturers of special materials for stabilizers. If
realized, they expect the tire to function like an active suspension, creating new value.
Making tire production sustainable
In addition to improving performance, a common challenge for the industry is how tomake the procurement of raw materials more sustainable. About 20% of raw materials fortires are synthetic rubber derived from petroleum, which emits CO₂ during production.
Natural rubber, which accounts for about 30% of the raw materials, is also faces supply
risks due to disease and natural disasters, as about 80% of the para rubber trees used as
raw materials are unevenly distributed in South-East Asia.

In order to make tire production sustainable into the future, companies are rushing todevelop tires made from recycled or renewable materials. In addition to polyester yarnderived from plastic bottles and silica derived from rice husks, they are working on
demonstration tests to extract carbon black and other materials from waste tires. Toyo Tire
Corporation is engaged in joint research with the University of Toyama on the practicalapplication of a catalyst for synthesizing butadiene rubber from CO₂.
The search for alternative raw materials for natural rubber also continues. BridgestoneCorporation is researching ’guayule' shrub, while Sumitomo Rubber is working on
producing rubber from 'Russian dandelion'. Bridgestone Corporation has already started
using guayule-derived rubber for racing tires. Domestic and foreign manufacturers have
set the goal of achieving '100% Sustainable Tires’ in 2050, and are initially manufacturing
prototypes and for limited applications such as for racing.
Sumitomo Rubber Industries, Ltd. unveiled tires made from 80% sustainable raw materials
last year.
Many manufacturers have set an intermediate target for the use rate in 2030 forcommercial products as well, and they intend to make a concerted effort, from researchingraw materials to increasing supply, developing supply networks and appealing toconsumers for their value.
Mobility is undergoing a major transformation, including electrification and automateddriving. However, even as power sources and usage scenarios change, tires remain anindispensable part of land transportation. Tire manufacturers will continue to evolve tire
products to meet new needs and support mobility.