Magazine for the professional tire industry
Issue link: https://mtd.epubxp.com/i/148910
Several OEMs have designed concept cars that feature tall, thin tires. Te 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. Te Audi Urban Concept car has 125/60R21 tires in front and 145/50R21 in the rear. Te 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. Te company estimates that 2.8 million electric vehicles will be registered worldwide by 2020. Te 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 fexible sidewall helps conserve energy loss when defecting or rebounding. "Te height is because the increased outer diameter of the tire improves rolling resistance signifcantly 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. Terefore, the size strategy should be to get as tall as possible with respect to the overall tire/vehicle performance. Te narrow size improves the aerodynamics of the tire." Bridgestone Corp.'s Ecopia ologic tire, size 155/55R19, has a larger vertical diameter and increased air pressure to limit changes in the contact patch. Introduced as the Large and Narrow concept tire, it is now in production, the company reports. 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. Te result is that the new size for a 205/55R16 is 195/55R20. "Tis was tested in the eContact project with great success. Other sizes are, of course, also possible and in development for some OEMs," says Strübel. "Our concept is to keep the tire pressure constant due to the same load index of the new tire size." "Very simplistically, the skinnier the tire, the less material that's The Volkswagen XL1, a production vehicle available in Europe, has Michelin Energy tires size 115/80R15 on the front and size 145/55R16 on the rear. Volkswagen Group of America says it can get up to 262 mpg. www.moderntiredealer.com 27