Revision 9 – December 21, 2007 

New Generation Wide Base Single Tires 

Background 

New Generation Wide-Base Single (NGWBS) tires were designed to replace a set of dual tires at the 

tractor drive and/or trailer positions. They were designed to be interchangeable with the dual tires 

without any change to the vehicle. The new 445/50R22.5 tire replaces 275/80R22.5 duals, and the 

455/55R22.5 tire replaces either 11R22.5 or 275/80R24.5 tires. Both Michelin and Bridgestone offer 

the 445/50R22.5 size while only Michelin offers the 455/55R22.5 size of these new tires. 

Goodyear has not yet entered the market. The information contained in this document was collected 

from ATA members and published sources. It is meant to be a summary of available information at 

the time of publication. 

Advantages 

The main advantages are that the new wide base tires weigh less than duals, approximately 800 lbs 

less when combined with aluminum wheels on a five axle combination, and fleets have reported 

savings ranging from 1% to 8% on fuel on the same combination vehicle. This amount of fuel savings 

is not easy to obtain, and where the weight savings can be exchanged for payload there is an even 

better return. The use of these tires is recognized by EPA’s SmartWay Transport Partnership as a 

clean freight strategy by their ability to reduce fuel consumption. A SmartWay study published as an 

SAE paper showed reduction in fuel use of 6% at 55 mph, 12% at 65 mph and 10% in a suburban 

loop. The NOx reductions were 36%, 30% and 13% respectively. 

Advantages of NGWBS tires can include reduced tire wear in some applications, increased payload 

capacity due to lower weight, improved fuel efficiency, and improved vehicle ride and handling. 

Ultimately this should result in improved profits for motor carriers. The NGWBS tires were developed 

using parameters provided by state highway agencies to minimize any negative effect on pavement. 

They meet the inch width-weight limits for all states, but are restricted in certain states to 17,500 lbs 

on a single axle at 500 lbs/inch width limit, and are disallowed on single axle positions on certain 

double and triple combination vehicles. The NGWBS tires are not to be confused with the “old” 

“Super Singles” used primarily on construction vehicles. That would be like comparing old bias ply 

tires to new radials. 

Information on the NGWBS has been slow to come out since their introduction in 2000, but most poor 

perceptions are diminishing. These perceptions include safety issues related to sudden deflation, 

increased pavement damage, and lack of availability in the field. Poor perception by some could also 

be based on some truckers running with one dual tire at each wheel end on axles designed for two 

duals. 

There have been many tests conducted to prove that NGWBS do not pose a handling problem in 

event of sudden deflation, this is supported by real world experiences. Many tire issues today are the 

result of under inflation. The fact that the inner dual is sometimes difficult to check compounds this 

issue. This situation is improved with the use of NGWBS, enhancing ease of tire maintenance and 

reducing the potential for field problems. 
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Although not a requirement, tire pressure monitoring systems can help drivers’ awareness of the air 

level in WBS tires. This may prevent premature air loss and reduce the number of flat tires. Many 

users have also cited that the brakes stay cooler on their vehicles due to improved air flow with a 

WBS tire and wheel set up. 

Comments from fleets in northern climates include improved traction and feel in snowy conditions. 

When designed as original equipment on tankers, the center of gravity can be lower due to more 

space between the inside side walls on WBS tires compared to a dual set. 

Overall availability has improved significantly and continues to improve as more fleets adopt the 

technology. Fleets report that availability is no longer an issue. Since they are interchangeable with 

standard size duals, a pair of tires and wheels can be purchased in an emergency. 

An occupational benefit is a proven reduction in dolly maneuvering force providing a safer 

environment less likely to cause injury. Fleets have reported dramatic reductions in back injuries from 

maneuvering and hooking up dollies. Drivers have also widely reported favorable on-road handling 

characteristics. 

The Technology and Maintenance Council of the ATA has drafted a Recommended Practice (RP) 

“Guidelines for Outset Wide Base Wheels for Drive/Trailing Axle Applications”. The RP will discuss 

the effects on wheel bearing load with the WBS shift of centerline from duals.. 

Finally, NGWBS appear to result in less scrap since they contain fewer sidewalls compared to a pair 

of dual tires. This, however, depends on the number of miles between retreading and the number of 

times that is done. Although some users have reported that they have successfully re-treaded WBS 

tires two times with no issues. 

Disadvantages 

One down side is that until the entire fleet has converted two sets of wheel hardware must be 

maintained. In some operations such as a 10 ft spread tandem these tires are reported to have 

durability problems. Just as there have been reports of better tread wear than duals in some 

applications, there have been reports of less tread wear in other applications. Mixed results on wear 

have come from members we have polled. The jury is still out on whether these NGWBS have 

comparable tread wear to the duals they replace, or if they can be successfully recapped the same 

number of times. It appears that local or city operation, as well as spreadaxle applications, can result 

in significantly faster tire wear due to curbing, stone drilling, and scrubbing. 

Some fleets have reported higher scrap rates for casings (as high as 40%). Today these tires only 

represent an estimated 0.5% of the 17.5 million tires sold each year in the US. For trucking 

companies operating cross border operations, the fact that these NGWBS are not allowed in Canada 

can be an issue. 

While the older “Super Single” tires increased wear on pavements, these new tires are wider and can 

operate at lower air pressures. They have been measured to be close to neutral as far as road 

damage. 

Through studies conducted by Dr. Al-Qadi of the University of Illinois Urbana-Champlain, NGWBS 

tires have been found to produce slightly more stress and strain under the top layer of asphalt layer 

(HMA) than traditional dual tire assemblies. This type of wear is related to fatigue damage. However, 
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he emphasizes the amount is negligible. In the same studies, NGWBS are also less damaging to 

pavement in top down cracking, which is initiated by tire edges. NGWBS have only two edges 

compared with traditional wheel ends with four edges, thus they stress the road less in that mode. Dr. 

Al-Qadi is continuing his studies and improving the modeling software to analyze road stress from 

tires. 

Other studies in addition to Dr. Al-Qadi’s, have been completed on NGWBS tires, both independent 

and sponsored by manufacturers, while varying in results, the effect of the NGWBS on roadways is 

comparable to that of dual tires. Steer axles are still the primary source of road damage. 

However, at present time the biggest disadvantages of NGWBS tires may be out-of-date state laws 

and regulations still on the books which restrict the use of single tires, intended to prevent “singling 

out” of wheel ends designed for dual tires, as well as regulating the previous era of “Super Singles”. 

ATA engineering has a spreadsheet available of the latest regulations that prohibit “single” tires that 

can be interpreted as a prohibition on WBS tires also. Work is ongoing with the states to clarify 

regulations. 

Conclusions 

The potential benefits to ATA members include improved fuel economy , reduced un-sprung weight 

(~700 lbs/ five axle combination vehicle) which helps improve handling, lower cost (~$130/wheel end 

for certain applications), reduced maintenance and improved safety due to improved ride and 

handling in all weather conditions. 

These benefits would have to offset the wear and recap questions mentioned above to complete the 

payback picture. Users need to consider their application, dollars saved, and return on investment. 

Further testing is expected to be completed and will be followed closely by ATA Engineering to verify 

whether the NGWBS tires continue to be a positive change. 

Study and knowledge sharing on WBS tires is continuing with a consortium led by the Federal 

Highway Administration. The first meeting had representation from academia, government agencies 

including Canada, France and South Africa, tire manufacturers and end users represented by ATA. 

For additional information please contact: 

Brian Routhier 

Engineering 

703-838-7933