What is understeer?

If oversteer is when a vehicle steers into a corner more than you expect, understeer is the opposite.

We use both of these terms to describe the dynamic balance of a vehicle when cornering.

In the most basic explanation, understeer is when a car wants to continue more or less in a straight line rather than steering into a corner. In effect, the mass, and or the drive of the car, overpowers the front wheels’ ability to initiate and continue the turn.

In a worst-case scenario, more steering effort (lock) simply induces more tyre squeal without changing the angle of approach to the corner – this can also manifest itself by the steering becoming very light through the wheel.

There are many reasons a car may understeer. Cars with significant front-weight bias are notorious lead-tip arrows (think about it – an arrow doesn’t go around corners). Ironically cars with insufficient front-end grip (or weight) can also be prone to a loss of front-end grip. Even a sports car with a rear-end bias such as a Porsche 911 can surprise a driver by failing to turn in when the driver hauls on the wheel.

Front-drive cars have both a significant front bias in terms of weight distribution and also ask a lot from the two front wheels – to provide drive and steering. It’s not surprising they have a reputation for understeer characteristics.

Like many ‘rules’ this is not a given. Even front-drive cars can be ‘tuned’ to be neutral or indeed, lose grip at the rear wheels first, for an oversteer situation. Front-drive rally and race cars are often witnessed with the tail sliding out around a bend.

Most typically in the case of road cars, understeer is a result of ‘pushing’ your car through a corner rather than ‘carving’ through it on a proper line.

In front-drive cars, too much throttle when you turn the wheel (especially if it’s wet or greasy) will see the front end of the car push wide. The remedy is simple, ease off the throttle a little to allow the front tyres to regain their grip.

Rear-drive cars can lose grip at the front, just like front-drive cars. More often that not this is a result of hitting the brake pedal too late as the car enters a corner. It's a problem more often encountered in older cars, with poor suspension geometry and a lack of advanced safety systems to correct the loss of adhesion between the rubber and the road. Easing off the brake pedal and letting the rear-drive car drag itself around the corner on a 'trailing throttle' can improve the car's line through the corner.

Often the driver who doesn't fully appreciate his or her car's roadholding limits may unwittingly exceed those limits for the front wheels by braking harder than necessary. This upsets the vehicle's balance. Lifting the foot off the pedal can allow the car to regain front-end grip and it will promptly return to its intended course around the bend.

A car with understeer characteristics is sometimes described as ‘tight’ by drivers.

Because mild understeer makes cars easier to drive for a range of skill levels, road cars, even high performance examples, tend towards this handling trait in their chassis balance. It's a handling trait that's not as 'nervous' at high speeds, so it's often chosen for grand tourers and luxury sedans that spend more time on freeways. In contrast, a sports car may be tuned for natural oversteer to promote 'playfulness' at low speeds.

On a racetrack, a professional driver can overcome mid-corner understeer by powering up the engine of a rear-drive car and breaking traction at the rear wheels. For road users, electronic anti-lock and stability control systems have been developed to retain steering even when the car is braking in an emergency situation.