What is oversteer?

The dynamic balance of a vehicle when cornering is often described using the terms oversteer and understeer.

In simple terms, oversteer is the condition where a vehicle steers into the corner more than the driver expects for the amount of steering lock applied.

In extremis, one or both of the rear wheels loses grip and slides laterally across the road surface. This will see the rear of the car depart on a different track and the car swings around to face the inside of the corner. When controlled, this is often called a drift. It’s fun – sometimes – and drifting is now an officially approved category of motor sport competition.

Professional drifters will initiate extreme oversteer by hauling on the car's hand brake while it's travelling at speed. This will break the grip between the wheels at the rear and the road. The driver also presses the accelerator to spin the rear wheels, ensuring neither tyre at the rear regains traction (grip). With appropriate steering corrections, this keeps the car in a 'tail-out' attitude.

There are many reasons a car might oversteer and many, many factors that dictate the amount of oversteer and the overall the dynamic qualities of a vehicle.

Most typically in the case of road cars, oversteer is a result of very aggressive weight transfer as a driver brakes hard and turns into the corner simultaneously. This can occur in all types of vehicles but is more common in sporty front-drive cars where this characteristic is utilised to increase the agility of the car.

Overdone, this can upset the balance of the car and cause dangerous characteristics.

In rear-wheel drive cars, over aggressive use of the throttle when cornering can overpower the grip of the rear tyres and induce throttle-on oversteer. Or to put it another way: heavy application of the accelerator will spin up the engine and break traction at the rear.

A car with oversteer characteristics is sometimes described as ‘loose’ or ‘pointy’ by drivers. Because this characteristic makes cars easier to get into a corner (to a point!!!), sports cars and racing cars sometimes tend to a tuned oversteer trait in their chassis balance.

Many drivers lack the experience or aptitude to control a slide, which is why stability control was developed – to reduce the danger of sliding sideways into a light pole or tree.

Drivers who have practised correcting a slide know that when the rear of the car is sliding right (and the nose of the car is thus pointing further left), turning the wheel to the right will ensure the car is pointing back towards the intended line of travel.

If the car is sliding left (with the nose pointing further right), the wheel should be turned left. The basic message is this: keep the front wheels turned in the direction you want the car to travel, not the direction physics wants the car to take.

It's not enough to correct the steering alone, however. The driver needs to correct the throttle or braking action that created the slide in the first place. In a rear-drive car, that usually means smoothly easing off the accelerator.

For a front-drive car, lifting off the brake pedal and gently applying more accelerator may help.

Adjustment of braking effort or the accelerator setting should take place as the driver is counter-steering (also known as applying opposite lock) to reimpose control of the car and counteract oversteer.

If the driver does one or the other, but not both, he or she will have to twirl the wheel back and forwards rapidly as the car fishtails down the road. This wild pendulous sliding is also often known as a 'tank slapper'.

It takes some practice to correct oversteer and even more practice to maintain the car's slide in a constant arc.

It's certainly not something to try on a public road.