Car Handling Basics

There are a number of aspects to your car's handling and cornering ability that we need to understand in order to fully appreciate our discussion on suspension tuning. We'll begin by looking at the various conditions and properties that affect your car's handling, and the different characteristics of road holding.
UNDERSTEER, OVERSTEER, BUMP STEER AND ROLL STEER

The terms understeer, oversteer and bumpsteer refers to the car's steering characteristics that are affected by the car's suspension settings. Understeer and oversteer occurs under cornering conditions, while bumbsteer (and roll steer) occurs when negotiating rough road conditions.

* Understeer occurs when the front wheels of the car tends to lose grip and drifts towards the outside of the turn, giving the impression that the car is straightening, or not turning in enough. The suspension setting on most stock cars tend to favor understeer. This is because understeer is seen as a safer option than oversteer for the average driver as the correction is instinctively accomplished by reducing speed or turning more into the corner.
* Oversteer occurs when the rear wheels the car tends to lose grip and drifts towards the outside of the turn, giving the impression that the car is turning in too much. The driver must counter oversteer by straightening the car a little otherwise the car will spin if it is pushed to its limit. Oversteer on rear wheel drive and all wheel drive (AWD) cars is sometimes useful for the experienced driver who can use the power to the rear wheels to balance the steering through the corner, allowing the driver to come out of the corners at higher speeds.
* Bump steer results from the suspension geometry occurs when the toe angle of the front wheels change as the suspension moves in an upward (bump) or downward (drop) motion as it negotiates the bumps over a rough road surface.
* Roll steer is similar to bump steer but occurs when the toe angle of the front wheels change as the suspension moves in an upward due to body roll.

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