Monday, August 12, 2013

Is this the tire of the future?

The skinny on tall, thin tires
Is this the tire of the future? Or just an electric vehicle trait?
The Volkswagen XL1, a production vehicle available in Europe, has Michelin Energy tires size 145/80R15 on the front and size 145/55R16 on the rear. Volkswagen Group of America says it can get up to 262 mpg

They were on the Ford Model T a century ago. They were on the Citroën 2CV in the 1950s. Today they’re on hybrid and electric concept cars. They’re also used in racing.
Are tall, thin tires going to be the next big trend in the tire industry?
That’s what we asked the five largest tire manufacturers in the world: Bridgestone Corp., Continental AG, Goodyear Tire & Rubber Co., Groupe Michelin and Pirelli & Cie SpA.
Some were forthcoming with details and information; others, not so much.
“We are constantly working on many technical projects, but we don’t always want to talk publicly about them,” a Goodyear spokesperson told Modern Tire Dealer.
Two other tire companies also declined to participate in this story at first, then later agreed to. Two of the tire makers would not comment on the details of manufacturing tall, thin tires. Two would not discuss the tall, thin tires their companies offer.
There appears to be a great deal of secrecy surrounding the design of tall, thin tires. One thing is certain: There is a trend for better fuel economy in vehicles, and tires play a significant role in the equation. Less rubber on the road means better rolling resistance, less noise and less wasted energy.
Several OEMs have designed concept cars that feature tall, thin tires. The BMW i3 Concept Coupe, unveiled at the 2012 LA Auto Show in November, has tires size 155/60R20 up front and 175/55R20 in the rear. The Audi Urban Concept car has 125/60R21 tires in front and 145/50R21 in the rear. The Volkswagen XL1, a production vehicle that is available in Europe, has Michelin Energy tires size 115/80R15 on the front and size 145/55R16 on the rear.
As OEMs develop more electric vehicles and hybrids, tire makers continue to develop taller, thinner tires to go on them.
Continental AG says that the Conti.eContact, introduced in 2012, is pioneering tire dimensions for the growing electric vehicle market. The company estimates that 2.8 million electric vehicles will be registered worldwide by 2020.
The Conti.eContact’s dimensions include a larger outer diameter, and the size is 195/55R20 instead of a traditional 205/55R16, resulting in reduced rolling resistance. A more flexible sidewall helps conserve energy loss when deflecting or rebounding.
“The height is because the increased outer diameter of the tire improves rolling resistance significantly due to reduction of tire deformation,” explains Dr. Christian Strübel, head of Continental AG’s Expert Field Rolling Resistance PLT Tires Business Unit in Hannover, Germany.
“A 1% outer diameter increase results in approximately a 1% rolling resistance reduction. Therefore, the size strategy should be to get as tall as possible with respect to the overall tire/vehicle performance. The narrow size improves the aerodynamics of the tire.”
Strübel says Continental’s tall, narrow size concept focuses on reducing the section width by 10 mm to improve the aerodynamics of the tire while keeping the aspect ratio constant to conserve handling. Next, the rim size is increased by four inches. The result is that the new size for a 205/55R16 is 195/55R20.