Thursday February 20 2014

Pocket dictionary : Oversteer and understeer

By Mustafa Ziraba

When you turn the steering wheel in your car, you typically expect it to go where you are pointing it. At slow speed, this will almost always be the case but once you gain some speed, you are at the mercy of the chassis and suspension designers. says in racing, by design the car’s suspension and chassis help to maintain an even balance of the car in corners along with the position of the weight in the car. At high speeds when going into a corner, the two most common problems you will run into are understeer and oversteer.

Less steering
Understeer is so called because the car steers less than you want it to. Understeer can be brought on by all including chassis, suspension and speed issues but essentially it means that the car is losing grip on the front wheels. Front wheel drive cars generally understeer. That is to say that when turning a corner, the front wheels are performing both the action of changing direction, and moving the car forward. The faster you are travelling, the harder it is for the front wheels to perform both actions at the same time.

At this point the grip of the front tyres is simply overpowered and they start to lose grip for example on a wet or gravel road surface causing you to turn in a wider arc than if you would been driving slower. The wider the arc, the more you are understeering. In racing, that normally involves going off the track and hopefully not into fans. In normal you-and-me driving, it means crashing at the outside of the corner. Getting out of understeer can involve getting off the accelerator and not pressing the brake in front-wheel-drive cars giving the tyres chance to regain grip.

On the hand, as you might have guessed, is that oversteer the opposite of understeer. Rear wheel drive cars generally oversteer. With oversteer, the car loses grip on the rear wheels as the weight is transferred off them under braking or hard acceleration, resulting in the rear kicking out in the corner.

Without counter-steering the end result in racing is that the car will spin and end up going off the inside of the corner backwards. In normal you-and-me driving, it means spinning the car and ending up pointing back the way you came. In the Fast and Furious movies specifically Tokyo Drift, you shall see a lot of “drifting”, where the car is driven around a corner almost sideways, with the front wheels turned in the opposite direction, that is simply controlled oversteer.

Overcoming both
Both under and over steering are scary experiences for normal drivers. Both scenarios have common causes including entering a corner too fast, accelerating or braking too aggressively in a corner, and the road conditions in a corner. Regardless of the vehicle, the best way to avoid oversteer or understeer is to drive within one’s limits, in a manner appropriate to conditions.