Understeer and oversteer – and why they happen
Unless you are keen driving enthusiast, you may hear terms like understeer and oversteer and wonder what people are on about. Surely it’s nothing to do with me and my normal car, you might think. Yes, they are specialist terms used to describe the way a car handles during cornering. Yet all drivers could benefit understanding what they mean, how to avoid them – and what to do if you experience either of them on the road.
What is understeer?
Drivers experience understeer when they try to steer into a turn, but the car wants to carry on straight. It is most likely to happen if you enter a corner too fast or there’s something slippery on the road surface.
Cars with front-wheel drive - like most hatchbacks and many small SUVs - can be more prone to understeering in corners than rear-wheel drive cars if you drive them too fast or aggressively. That’s because their front wheels have a high workload as is, handling the steering, most of the braking effort and - as the term front-wheel drive explains - the actual propelling of the car.
If you then add in a high amount of extra work due to aggressive driving, they can break traction and start to skid or slide on the surface. If that happens, the car's direction of travel will likely be straightened out, so if you're in the middle of a turn, you'll 'under steer'. That can be dangerous, especially if you're on a narrow country road and there's not much room for error.
What is oversteer?
As the name suggests, oversteer is when the car steers too much in a direction. This is more likely to happen on a rear-wheel drive car, because the delivery of power is to the back wheels. If your powered wheels lose grip in slippery conditions or because you've accelerated too hard, making them break traction with the tarmac, then the back of the car can swing around. Driving enthusiasts will know this as 'power oversteer'.
It looks fun when TV presenters do it on a race track and expert drivers can control the oversteer during cornering, like top rally drivers. Neither of these has to deal with traffic coming the other way. Oversteer can be very frightening and dangerous on a normal road if you've never experienced it. It can end with the car completely spinning around.
Oh, and it's not exclusive to rear-wheel drive cars. Front-wheel drive cars can oversteer, but it's not due to power, but rather aggressive driving or braking too hard while turning. See our hot hatch head-to-head video below for plenty of deliberate examples of front-wheel drive oversteer. Definitely don't try this at home.
How to avoid oversteer and understeer
Drive safely at moderate speed and adapt to road conditions correctly and you are unlikely to experience either. Modern tyres have better grip and cars often have anti-skid safety systems, including anti-lock braking tech.
The key to always driving safely is smooth operation of the controls. Avoid oversteer and understeer during cornering by gradually releasing the accelerator or gently increasing pressure on the brakes, rather than making sudden inputs.
Steer smoothly into corners with easy relaxed movements that won’t upset the balance of the suspension and grip of the tyres.
What to do if you sense understeer or oversteer
The experts’ secret is to turn in the direction of any skid to regain control and then steer to safety. That’s easier said than done in the heat of the moment. Skid-pan training is usually needed to be able to get yourself out of a severe dangerous skid.
Instead, concentrate on keeping your responses smooth. Reduce your pressure on the accelerator or brakes gradually. Whatever you do, don’t stamp on either pedal or jerk the steering wheel in a panic.
Consider the road conditions
In any icy, snowy, rainy, muddy, gravelly or sandy conditions your tyres’ grip is reduced. This makes understeer and oversteer much more likely. The simple answer is to reduce speed in any difficult conditions like these and tackle any corners with much greater care. This is true even for all-wheel drive cars, which can understeer and oversteer just as much as their counterparts in slippy conditions. Stay smooth. For more advice, see our snow and ice driving advice page here.
What else affects understeer and oversteer?
Tyres! There’s a reason experts are always banging on about tyres. Those four little patches of rubber are the only way of controlling your car. Make sure you have the right tyres fitted, keep them pumped up to the correct air pressures and check that the tread is above the legal limits. Worn or wrongly inflated tyres vastly increase the chances of understeer or oversteer. Cheap tyres will typically have less grip than higher-quality ones, so we'd recommend only opting for known brands.