Skids and slides: Managing oversteer (it's shorthand for 'sideways')

But how many different kinds of oversteer do you think there are?

Classic oversteer - driver needs to steer right to negotiate a left-handerThere are two 'flavours' of sideways in a car - but let’s recap. Oversteer is where the rear wheels lose traction first. The car turns (or ‘yaws’) harder into the corner than its steering input would otherwise dictate, it literally over-steers - hence the name. From the driver’s seat, you notice the rear end trying to overtake the front. The car goes 'sideways'. It is unnerving, especially for passengers and other road users, which is why it’s best experienced at a driver-training course, not on the drive home from work.

Oversteer come in two ‘flavours’. The first is power oversteer; the second, throttle-off oversteer. Two completely different causes; two completely different cures. One is often a high-speed experience, the other more mundane. Getting them mixed up would be bad.

Problem One

Power oversteer: you’ve seen the ute ad, been to the B&S ball, done the circle-work, right? Power oversteer typically occurs at low speed, because in most cars there’s not enough torque multiplication in the higher gears to break traction at the rear wheels in most cars (unless you own a GT2, a DB9 or an F430 ... or live or drive to work on an ice floe).

Typically, you stop at a T-junction, give it a big boot in first (rear-drive car, traction control off), the rear wheels break traction and the skatey rear end pirouettes about the front. Watch that power pole at nine (or three) o’clock.

The cure? Less right Blundstone. Reduce the accelerator input. If you notice the problem early, say before you’re at 45 degrees to the intended direction of travel, the situation may be salvaged. Button off, and keep the steering wheel pointed in your intended direction of travel. (Look where you want the car to go; that ALWAYS helps. Very important skill.) This process may involve steering, say, left in a right-hand bend, which is where the term ‘opposite lock’ originates. As the car snaps back into line, adjust the steering. Keep looking where you want the car to go - it makes the whole problem so much easier to solve.

Problem Two

Throttle-off oversteer has more to do with weight transfer and dynamics than sheer grunt, and it afflicts all drivelines, front, rear and AWD. It also happens faster, at higher speeds, and requires more finesse and finer perception skills to control.

It happens like this. You’re into a bend, near the limit of adhesion. The chassis is basically neutral (meaning all four wheels are right up against the limit). You chicken out, declare you’re going too fast, and lift off the throttle. Oops.

What happens? When you lift off, the car decelerates. Weight transfers forwards, so there’s a little more weight on the front wheels, a little less on the rears. Consequently, there’s more steering input at the front, so the car turns harder. At the rear, less weight means less grip, so the rear end breaks traction and slips sideways, abetting the front. Suddenly, you’re in a high-speed, throttle-off oversteer slide.

The cure? Balance the car on the throttle. Meaning apply a little more throttle (don’t boot it, however) until additional rearward weight transfer adds rear grip. All the while, keep the steering pointed where you want the car to travel - down the road, in your lane. (See the note above about looking exactly where you want the car to go - a vital car-control skill.) Don’t give up, even if the 'sideways' moment is a big one, because sliding cars are also rapidly slowing ones. Grip is nearly always restored at lower speeds, which is a good thing - unless your steering wheel is pointed catastrophically off course when it happens.

The earlier you recognise either of these two problems, and take corrective action, the better. Problems like these go away a lot easier with the benefit of early detection and corrective actions.

safetyJohn CadoganComment