Understeering, Oversteering

 

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're travelling, the harder it is for the front wheels to perform both actions at the same time, without causing you to turn in a wider arc than if you'd been driving slower.

The wider the arc, the more you're understeering.

To counter understeer, you have to reduce speed by lifing off the gas.

Rear wheel drive cars generally oversteer.

The rear wheels only move the car forward, and the front wheels only have to change the car's direction.

Oversteer means that the arc is much tighter as the rear of the car tries to 'come around' to the front. Worst case scenario is spinning out.

You can counter oversteer by applying more speed, and by turning the wheel in the opposite direction -- 'opposite lock'. (Lifting off the gas during oversteer will cause a weight transfer to the front of the car, reducing grip at the rear which is not good in a rear wheel drive car.)

If you've ever seen 'drifting', where the car is driven around a corner almost sideways, with the front wheels turned in the opposite direction, that's oversteer.
If you're inexperienced with a rear wheel drive car, take it easy. It can take a lot of practice to be able to effectively balance an oversteering car with throttle and steering input. Applying too much opposite lock and the car can begin to oversteer in the opposite direction! Fishtailing is a scary experience!

======

Have you heard the ｅxpressions, a particular car oversteers or another one understeers? Do you know exactly what is meant by each term? If you had a choice, which one would be safer to drive?

 

Let's look at what is really meant by both ｅxpressions. Imagine you are in your car on a large empty parking lot, with nothing around the lot to hit, no poles or other cars.

Now you start driving and turn the wheel either right or left so that you will be driving in a circle. No problems, you are slowly driving in this big circle and everything is under control.

Now imagine that you are going a little faster, and faster around the circle. Soon you will start to hear some tire noise. As you increase your speed the sound becomes louder and the tires start to squeal. Soon they are squall ing and you know that something is about to happen.

If it is becoming harder and harder to keep the front end turned in on your circle. That is, if the circle is becoming larger as you speed up, then your car understeers.

If on the other hand, the rear end of your car seems to be sliding away and seems like you will be going sideways or backwards in a second, then your car oversteers.

UNDERsteering cars lose the tire grip at the front of the car and OVERsteering cars lose the tire grip at the rear of the car first.

 

So which one is safer?

Almost all car manufactures design cars so that they understeer.

This means when you drive too fast on a curve, and the front end is harder to turn

you almost instinctively back off of the accelerator pedal. The car slows down and regains its grip and you go around the curve a little slower and safely.

This is fine for a typical car and average driver.

 But if you are in a race car, or a car designed to run on a race track, you want a car that oversteers, because you let the rear end slide out a little. This points you more into the turn and you can go faster. However, you must have the driving skills to overcome the slide while you go around the curve. Or you will slide out of control, something that's not too bad on a race track, but can get you killed on a city street.

Dennis Dater has been involved with cars for over 50 years. His first love was sports cars when he drove a 1952 MG to high school. He has produced over 50 articles for EzineArticles on cars, and almost a hundred on his web sites. His two web sites are designed for Honda Accord aftermarket accessories