Grassroots Motorsports
Issue link: http://grassrootsmotorsports.epubxp.com/i/501675
Grassroots Motorsports 121 FEATURE: STREET TIRE TEST G r a s s r o o t s M o t o r s p o r t s 1 2 1 now getting tweaked on a one- or two-year basis. Many times the upgrade comes courtesy of a new compounding technol- ogy–often a silica variant–that improves durability and allows for more grip across wider temperature ranges. At the same time, tire makers are also pushing the limits regarding what constitutes a 200-minimum-treadwear tire–the restric- tion most sanctioning bodies have in place. We last tested this crop of tires two years ago, and the BFGoodrich g-Force Rival rose to the top. Since that time, Dunlop tweaked their Direzza ZII design with a Star Spec version. Hankook did the same with their Ventus RS3, though the offcial name has not changed–it's unoffcially known as the RS3V2 in the enthusiast community. Bridgestone brought out the all-new RE-71R to supplant the RE-11 and RE-11A. Then there's BFG's new sibling for their Rival, known as the Rival-S. It will be sold alongside the original. Each of these tires goes about its busi- ness in a different way. We designed our test not just to fnd out which one's fast- est on test day, but to elicit their unique characteristics so that you can decide which tire synergizes best with your own car, driving style and setup. In the past, we've typically tested tires on small, light, front-drive cars sporting fully sorted suspensions and wide wheels. This provides an optimal environment for the tire to show its prowess. We feel our method has bookended nicely with the comprehensive testing done by our friends at Tire Rack. They use heavy BMW 3 Series on narrow OE wheels–just like those running in the new SCCA Street classes. By viewing the data from both sets of tests, you can better match the results with your own application. Field of Battle We set up shop at the massive asphalt pad at Texas's Mineral Wells Airport in early April. It was a mild, sunny day with ambient temps rising from 55 to 65 during our testing period. The road surface cleans up quickly, but it is old and a bit abrasive. We've been testing here for years and have marked permanent skidpad and autocross courses. The latter is a simple loop affair, emphasizing handling over driver skill: a medium-speed slalom down one side, higher-speed offsets up the other, and a pair of constant-radius sweepers at each end. The site is on a slope, though, so one sweeper is on-camber and the other falls off. As it turns out, the entries to these two corners reveal the biggest differences between tires tested. Plan of Attack Leading the charge for the test were driv- ers David Whitener and Andy Hollis, both multi-time national champion autocrossers and veterans of GRM tire tests. David lives near the site and has literally thousands of laps around the Mineral Wells permanent test course. As a result, he knows its every nuance. The test vehicle for the day was the championship-winning, Street Touring R-prepped 1999 Mazda Miata of Michael and Kyung Wootton. The Woottons con- signed their Miata to David for suspension development, and he's already knocked a full second off the car's lap times. Because of his familiarity with both the car and the course, David served as our test's expert, someone who could quickly extract maximum tire perfor- mance. Andy played the role of guest driver, examining each tire's adaptability and ease of use. Note that the car's setup was based around the Toyo Proxes R1R, which is a tremendously forgiving tire. Dunlop Direzza ZII Star Spec Bridgestone RE-71R BFGoodrich g-Force Rival-S