Demystifying Understeer And Oversteer

Understeer

Understeer occurs when you are driving down a corner and the front tyres skid across the track surface due to a loss of traction, while the rear tires still have grip. You may notice that the vehicle is understeering because the resistance of the steering wheel is lower than usual and also because the car skids out of the corner, in a straighter line than the desired direction.

Oversteer

Conversely, oversteer happens when you enter a corner and the rear tyres lose grip and start drifting while the front tyres maintain their traction. You can tell the vehicle is oversteering because rear tyres start screeching at the time that the rear end of the car starts rotating around its axis toward the inside of the corner.

Why Do They Happen?

Both understeer and oversteer can happen for a variety of reasons including but not limited to errors in the handling of the car, weather conditions, inappropriate type of tires, a very soft or very rigid suspension, wheels alignment, engine’s power and torque curves, insufficient or bad adjustment of the vehicle aerodynamics, inappropriate weight distribution, tyre pressure, and more. Each track is unique, as is the ideal car setup to minimize understeer and oversteer issues.

How To Stop It From Happening?

There are many ways to negate (or at least minimize) understeering depending on what portion of the corner it happens in. When understeer happens at corner’s entry you can adjust front wheels alignment to increase camber and toe-out. You can also reduce front roll bar stiffness, reduce front shock absorbers firmness and lower the front of the vehicle. When understeer happens at mid-corner you may want to increase front springs pre-load, increase front sway bar stiffness or increase front spring rate. On the other hand, if understeer happens at the corner’s exit, you can increase rear roll bar stiffness, increase rear shock compression and rebound, raise rear height, or increase rear spring rate.

Similarly, you can overcome oversteer by making adjustments depending on what portion of the curve they happen. You can align the rear wheels to increase camber and toe-in, increase front roll bar and increase front shock absorber compression to control oversteer at corner entry. You can also reduce rear sway bar stiffness, reduce rear springs rates, decrease the ride height and increase rear camber to compensate for mid-corner oversteering. Moreover, you can reduce the rear height, decrease rear shock-absorbers’ firmness and reduce rear sway bar stiffness to fix corner exit oversteer.

During normal driving in the city or while commuting, you can reduce understeer by easing off the throttle (or the brake pedal if that was the reason for understeering). That way, the front tyres can regain grip allowing you to control direction again.

Controlling understeer is usually easier than oversteer, as it has more predictable results. During normal driving, oversteer is often caused by entering a corner with excessive acceleration causing the rear tyres to spin up and therefore lose traction. Another common reason is what is known as “liftoff oversteer,” which occurs when the throttle is raised too quickly when cornering, causing a temporary transfer of weight to the front. Depending on the case, you will have to turn the steering wheel gently in the opposite direction of the drift while smoothly applying the throttle (takeoff oversteer) or slowly releasing it to regain traction on the rear axle.

When Does It Happen The Most?

The chances of experiencing both understeer and oversteer are greatly increased when weather conditions are adverse because traction with the road surface is considerably reduced.

Under these circumstances, adapting your driving style is key to avoiding accidents. Remember, each time you enter a corner the centrifugal force exerted on the car has to be countered by the cornering force to avoid losing the grip on the tyres. You can’t change tyres, or adjust weight distribution on-demand, however, you can compensate for bad weather by decreasing speed and controlling the braking force applied.

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