Take for example, our test vehicle: a 2008 Mustang GT. The S197 platform (2005-2009) has been a huge success for Ford, as it offers good overall performance with strong acceleration and respectable handling in stock form. Ford outfits the GTs with Pirelli PZero Nero tires, which do a commendable job of putting the reins on the pony. The standard GT-issued Pirellis must work moderately well in all types of driving situations (wet and dry) and still cover the previously mentioned criteria that original manufacturers look for in a mass-produced tire. However, pick up the Mustang's pace on some twisty roads and the Pirelli's shortcomings quickly become apparent. Put simply, the Mustang GT is too much car for the narrow 235/55/17 Pirellis. The end result is a wild pony that drifts, slides and wanders around a corner.
Enthusiasts that appreciate a good handling car with lots of grip around corners will often ditch the stock wheels and tires in favor of wider (and nicer looking) wheels, which allow fitment of wider tires to increase road contact and grip. Moreover, just as critical to the footprint that a tire has is the design and compound of the tire. An ultra-high performance tire will, for the sake of maximum grip, forgo some characteristics that regular passenger tires (like the GT's stock Pirellis) have to worry about. For instance, an ultra-high performance tire will have a shorter lifespan due to a softer rubber compound that wears at a faster rate. In addition, wet weather handling may suffer slightly as ultra-high performance tires tend to favor dry road conditions due to their inherent shallow tread depths.
Since our discussion focuses on how to improve a Mustang's handling, we took our '08 GT to an autocross event for some hot-lapping and cone-crushing action. What better way to test and evaluate some easy handling upgrades than on a closed course where you are encouraged to drive as fast as you dare? Vehicle owner Robbie Grenda (of Redlands, California) was very generous in allowing us to torture, er, test, his car in the name of research. Also on hand were the skilled personnel of GTR High Performance (Rancho Cucamonga, California), who served as our pit crew.
The first order of the day was to run the GT in stock form with the original wheels and tires. After several laps, we had established a baseline from which to compare. In stock form, our average lap time was 54.65 seconds. Not bad, but the GT swayed like a small fishing boat in rough waters and the Pirellis howled for mercy around every turn.
Where the Rubber Meets the Road >>