Bridgestone: Taller, Skinnier Tyres For Better Fuel Economy

Larger diameter tyres with a narrow tread pattern will become the norm as the automotive industry trends towards green cars, says Bridgestone at the recent 2015 Tokyo Motor Show.

Among the exhibits was a solar-powered race car from the 2013 World Solar Challenge, built by the team from KoGakuin University.

The solar-powered car was running on Bridgestone’s Ecopia Ologic tyres. As seen in the following images, the Ologic tyres used by the solar-powered car looked more like a bicycle tyre than a car tyre. There are several reasons to that.

A larger diameter tyre will experience less tread deformation, as the curvature of its inner belt is less and the stronger tension has a stronger hold on the tread, as illustrated by the image below.

As a tyre rolls along a surface, some form of tread deformation is to be expected. As the tread deforms slightly, kinetic energy from the rolling tyre is lost. Thus, minimising tread deformation is one of the key focus in developing low rolling resistance tyre.

Secondly, a narrow tyre will experience less wind resistance. As wind resistance has a direct correlation with frontal surface area, a thin tread width will pay great dividends in improved fuel economy.

The image below illustrates the difference in coasting distance between a regular 205/50 R18 tyre and a ‘tall-and-thin’ 155/55 R19 tyre from the BMW i3 range-extended electric vehicle.

As you can see, the taller and narrower tyre are able to coast over a longer period of time than a regular wide contact patch tyre.

You would expect a tyre with such a narrow contact patch to have poorer braking performance, but Bridgestone says that’s not the case.

The contact patch for Bridgestone’s Ologic tyres is actually longer, and Bridgestone’s own data suggests that the Ologic’s wet braking performance is actually 8 percent better than conventional tyres.