'Torque vectoring' key to race tire development

GENEVA, Switzerland (March 7, 2013) — Dunlop Motorsport's long heritage of competition at the 24 Hours of Le Mans race will take a new turn — literally and figuratively — this year with the development of race tires tuned to the specific "torque vectoring" characteristics of the GreenGT H2, a hydrogen fuel-cell-powered prototype racer.

Torque vectoring—defined as a car's ability to vary the amount of power sent to each wheel—will exert "significant" influence on tire design in coming years as "alternative fuel" race cars become more prevalent, according to Sebastien Montet, race design and development manager for Dunlop Motorsport, an operating unit within Goodyear Dunlop Tyres Europe.

"Torque vectoring cornering control is often seen as the 'Hand of God' for corner capabilities on the track and the road in the future," Mr. Montet said, "but the substantial benefits of this technology counts for nothing without the appropriate tire design.

"Whilst the lateral torque distribution control unequally distributes the engine torque to the left and right wheels, torque vectoring technology provides the differential with the ability to vary the amount of power sent to each wheel, which results in optimum lateral acceleration. The suspension can therefore be used to control the vehicle response, whereas the torque vectoring focuses on the stability."

Dunlop has been developing technologies for hybrid, electric and alternate fuel cars for many years, but this development took on new significance recently when the business unit agreed to supply tires to GreenGT H2, a vehicle that uses a hydrogen fuel cell to drive an electric powertrain. GreenGT H2 will fill the 53rd starting spot reserved by the organizers of the annual Le Mans 24-hour endurance race for new technologies.

Mr. Montet said there are three main challenges for tire designers to overcome that will drive tire design for the future power of motorsport.

"With vehicles such as the GreenGT H2, we need to think about the vehicle weight, different engine characteristics and an improvement in fuel efficiency. A change in vehicle weight will mean an increase in the forces carried by the tire; different engine torque characteristics mean the tire requires an increase in longitudinal stiffness; and improved fuel efficiency will be optimized in lower rolling resistance in the tire we design."

In selecting a compound, Dunlop's engineers look at the optimum balance of the car at different tracks, surfaces and corners as well as factors such as controlling wear, reducing unneven wear, controlling tire temperatures and reducing rolling resistance, Mr. Montet said.

Dunlop has developed a "circuit characterization" process that uses lap time simulation to assess the work done by each tire and define a baseline compound layout for each circuit, he said. The use of different torque vectoring maps on a specific car could help or lead to rebalance compound and setup choices for each specific track.

"This type of race showcases the importance of fuel efficiencies to enable race teams to win on the track," said Sanjay Khanna, managing director, Dunlop brand. "After all, fuel is a weight in the car that hinders its performance. At the same time, the more fuel efficient a car is, the more laps it can run without needing to refuel—and lose time.

The emphasis on lower rolling resistance through lower heat generation compounds and optimized carcass shapes are the same design principles as in the new Dunlop Sport BluResponse road tire, also making its European show debut at Geneva, Dunlop said.

During 2013 the Dunlop brand is celebrating its 125th year in existence.