va122 wrote:I'm a little confused, why over inflate the rears versus the fronts to induce oversteer? Am I thinking about this too much that I'm confusing myself?
Over-inflating the rear tires will reduce traction on that end of the car and contribute to oversteering, with most street tires. Unfortunately, some of the newer cars with stock alignments have so much understeer built in at the factory that they are very difficult to "pitch and catch", even on low-grip, wet pavement. Even with all electronic traction control aids turned off, I have had to use left-foot braking as well as an abrupt lift of the throttle to induce enough weight shift to break the rear end loose on a stock 996 before when performing that exercise. Without some performance alignment changes, it is very difficult to get a newer Porsche to be "tail-happy," especially the C4S model. Of course with enough power, you can stomp on the throttle to spin the rear tires and break them loose, but that is more difficult to control in a tight turn and not the point of the exercise.
For safety's sake, over time the factory has eliminated the easy "throttle-steering" handling that was the hallmark of the early 911s. The newer, rear multi-link suspensions have much better toe and camber control in droop and compression than the earlier semi-trailing arm suspensions, which induced toe-out in a cornering situation when the throttle was lifted, resulting in instant (but very controllable) oversteer, when combined with the rear weight bias of the car. This had something (everything) to do with product liability. The initial solution was introduced on the 928 as the "Weissach axle", which added a toe-link to the trailing arm to control toe-out, and continued with the modern multi-link suspensions.
TT
Posted: Tue Apr 21, 2009 1:59 pm
