Originally Posted by abless
A problem related to front wheel drive setups. With RWD, no matter how much throttle you input, the pressure on the steering wheel remains basically the same. FWD likes to straighten out when aggressivly throttled because the same wheels being driven are being turned.
Understeer is when the front tires lose grip earlier than the rears, and the car wants to go straighter than the turn. This can happen just as easily with RWD cars, and is extremely prevalent in softly suspended front engine cars. Big engine musclecars were usually horribly understeering pigs when it came to cornering. So are most luxury sedans.
It's all about how much weight is transferred to the outside front tire in a corner, and how quickly the steering input is given.
Here's a Porsche oversteering. The car is going around a right hand bend, but the rear is turning more than the front, so the driver has to steer to the left to keep the car going around the corner correctly:
Here is a Porsche understeering. Notice how the front tires are turned more than the car is turning (and there is a dust trail showing thet the front tire is being dragged in the direction the car is pointing, not where the tire
This older RWD car is understeering heavily. The front tires are turned, but the weight transfer (as indicated by the body lean) is all the way on the outside front tire, which is not gripping well, and the car is going much straighter than the steering input:
The key to eliminating understeer is to keep the outside front tire from being overloaded. On a front heavy car, that usually means managing weight transfer away from the outside front tire using spring rates and swaybar size. the simplest solution is to increase the rear swaybar size (or install one if there isn't one). This transfers more weight to the inside rear tire, balancing the car out.