Bridgestone Explains New Fuel-saving Tire

May 9, 2014
Masaru Yoshida, Nikkei Monozukuri
The "ologic" tire has a narrower width, larger external diameter and less rolling and air resistances.
The "ologic" tire has a narrower width, larger external diameter and less rolling and air resistances.
[Click to enlarge image]
The "Ecopia EP500 ologic" of the BMW i3
The "Ecopia EP500 ologic" of the BMW i3
[Click to enlarge image]

Bridgestone Corp announced the details of the "ologic" tire technology, which improves fuel efficiency, at a press meeting that took place May 8, 2014.

A tire developed using the ologic has a narrow width, large external diameter and high air pressure. With the technology, Bridgestone improved drainage performance and gripping force of tire while reducing rolling resistance coefficient (RRC) and the air resistance of a running vehicle.

For example, when the size of the ologic tire is 155/55R19 (external diameter: slightly larger than 650mm), its load capacity is equivalent to that of the company's previous product whose size is 175/65R15 (external diameter: slightly less than 610mm). The air pressure of the previous product is 230kPa, and that of the ologic tire is 320kPa.

In general, RRC, which influences fuel efficiency, is determined mainly by the tread area of a tire, which is in contact with the road surface. For conventional tires, Bridgestone changed the properties of the materials used for their tread areas and reduced their weights. On the other hand, the company increased external diameter and air pressure for the ologic tire. As a result, it became possible to reduce the deformation of tread area while ensuring enough ground contact area, reducing RRC by about 30%.

In addition, the narrower width of the ologic tire reduces the air resistance of a running vehicle. The effect of improved air flow under the vehicle, which reduces air resistance by a few percent, is larger than that of the reduced air resistance of the tire itself. Fuel efficiency is expected to improve because of the reduced RRC and air resistance of the vehicle.

The narrower tire width contributes to improving drainage performance because it means a shorter drainage channel. It enables to reduce the size of the groove on the tire, and, therefore, rigidity can also be improved.

This time, Bridgestone developed a new tread pattern that has a narrow width and makes use of the high air pressure as well as a special rubber that is harder than a conventional rubber for treads. By employing them, the company increased gripping force while ensuring enough drainage performance, realizing a low fuel consumption and safety at the same time. In terms of cost, the new tire slightly increases processing cost, the company said.