If you have taken your car to a circuit you will be very familiar with understeer and oversteer. The two enemies of good lap times even if one of them is quite fun! Understeer is when the front of your car washes out towards the outside of the corner giving a lack of steering feel and pushing the car wide. Oversteer is when the back of the car swings out to the outside of the circuit, rotating the car and making it slide to the outside of the corner. Both are slower than maintaining grip around the corner with the few exceptions such as tight hairpin corners in rally situations where a dab of the handbrake can rotate the car faster than driving round it. However, for the purposes of this article we will focus on a tarmac circuit situation where you want to eliminate oversteer and understeer as much as possible.

The driving technique to reduce understeer is to let off the throttle to reduce speed and allow the front tyres to re-gain traction. To correct oversteer you should counter steer to prevent the car from spinning, and then reduce the amount of throttle enough to allow the car to begin straightening. However, do not fully let off the throttle once counter-steered as this will cause the back end of the car to grip immediately and will send the car in the direction of the counter steering front tyres, straight off the circuit most likely causing a crash or at least a bath in the gravel.  If you’re a regular at the circuit you will know these solutions so let’s look at some ways to reduce understeer and oversteer by altering the setup, allowing you to drive even faster.

There are also some generic solutions to solving understeer and oversteer. They are to shift mass to the sliding wheels to increase normal force at the tyre contact patch. Another is to increase the track width at the sliding end of the car. The other is to fit wider or a more grippy compound tyre at the sliding end to increase traction too. However, in most cases the above are not options, particularly in single make championships. For that reason we outline below how to solve understeer and oversteer by making alterations to geometry and vehicle set up which is far more applicable and useable information.

Understeer

The best way to solve understeer is to first answer a series of questions to identify exactly where and the when the understeer is occurring to apply the correct change to reduce/remove the understeer as much as possible. The first stage to check is if there is any friction or jamming of suspension components in the front suspension system as this can cause the front to jam and prevents the spring and damper from working.  If there is any sign of friction then solve that first.

With that checked the next step is to identify where in the corner the understeer is occurring. There are three options; corner entry, mid corner and corner exit. We will take you through each option below.

Corner Entry

The first question to ask now you have identified the understeer as occurring in corner entry is, are you entering the corner after being hard on the brakes? If the answer is yes then you have two options to solve the understeer:

1) Increase front damper rebound stiffness. If you have high or low speed damper adjustment then increase the low speed rebound stiffness only.

2) Reduce the front brake bias.

If the answer is no then you must ask yourself another question, are you entering the corner at high speed or mid to low speed? If the answer is high speed then one of the following options can be used to solve the understeer:

1) Reduce front ride height

2) Increase front aerodynamic downforce. If only the rear is adjustable then reduce rear downforce.

3) Check tyre pressures with a gauge to ensure that the tyres are operating within recommended hot temperatures. Increase or decrease pressures accordingly.

4) Check tyre temperatures with a tyre pyrometer and make sure that the temperatures are distributed by less than 30 degrees Celsius between edges with the inside being the hottest. If the inside is too hot then increase positive camber. If the outside is too hot then increase negative camber.

If the answer was mid to low speed then one of the following options can be used to solve the understeer:

1) Increase caster angle

2) Increase front toe out

3) Reduce front ride height

4) Check tyre pressures with a gauge to ensure that the tyres are operating within recommended hot temperatures. Increase or decrease pressures accordingly.

5) Check tyre temperatures with a tyre pyrometer and make sure that the temperatures are distributed by less than 30 degrees Celsius between edges with the inside being the hottest. If the inside is too hot then increase positive camber. If the outside is too hot then increase negative camber.

Mid Corner

The first question to ask now that you have identified the understeer as occurring at the mid corner section is, does the car bottom out? If the answer is yes then the below answers can solve the understeer:

1) Increase front coil spring rate. This can be achieved by installing stiffer springs or increasing pre-load.

If the answer is no then the next question to ask yourself is, does the front of the car roll excessively? If the answer is no then the following solutions can be applied:

1) Soften front coil spring rate

2) Increase front damper rebound stiffness. Front compression stiffness can also be reduced slightly.

3) Reduce front ride height.

4) Soften front anti-roll bar stiffness.

5) Increase negative camber on the front wheels.

6) Lower front roll centre or raise the rear roll centre.

7) Check tyre pressures with a gauge to ensure that the tyres are operating within recommended hot temperatures. Increase or decrease pressures accordingly.

8) Check tyre temperatures with a tyre pyrometer and make sure that the temperatures are distributed by less than 30 degrees Celsius between edges with the inside being the hottest. If the inside is too hot then increase positive camber. If the outside is too hot then increase negative camber.

If the answer was yes then the following solutions can be applied:

1) Soften front anti-roll bar stiffness

2) Increase front damper compression stiffness. Increase low speed if you have a high or low speed option.

3) Increase front coil spring rate.

4) Make sure there is no excessive droop in the front suspension causing the inside front to lose traction.

5) Raise the front roll centre.

Corner Exit

For corner exit understeer there are no more questions to ask. One of the following solutions can be applied:

1) Increase front damper rebound stiffness

2) Check tyre pressures with a gauge to ensure that the tyres are operating within recommended hot temperatures. Increase or decrease pressures accordingly.

3) Check tyre temperatures with a tyre pyrometer and make sure that the temperatures are distributed by less than 30 degrees Celsius between edges with the inside being the hottest. If the inside is too hot then increase positive camber. If the outside is too hot then increase negative camber.

Oversteer

The first stage to check is if there is any friction or jamming of suspension components in the rear suspension system as this can cause the rear to jam and prevents the spring and damper from working.  If there is any sign of friction then solve that first.

With that checked the next step is to identify where in the corner oversteer is occurring. There are three options; corner entry, mid corner and corner exit. We will take you through each option below.

Corner Entry

With the oversteer identified as occurring in the corner entry section, the first question to ask yourself is, are you turning into the corner straight after being hard on the brakes? If the answer is yes then one of the below options can be applied:

1) Slightly reduce rear damper rebound stiffness

2) Reduce rear brake bias

3) Check tyre temperatures with a tyre pyrometer and make sure that the temperatures are distributed by less than 30 degrees Celsius between edges with the inside being the hottest. If the inside is too hot then increase positive camber. If the outside is too hot then increase negative camber.

If the answer is no then you must ask yourself another question, are you entering the corner at high speed or mid to low speed? If the answer is high speed then the below areas can be applied to the car to solve the oversteer:

1) Increase rear aero downforce

2) Reduce rear ride height

3) Slightly increase rear toe in

If the answer is mid to low speed then another question must be asked, is the car lifting a wheel at the rear? If the answer is yes then one of the below solutions can be applied:

1) Increase droop on the rear wheels to ensure that the tyre stays in contact with the ground.

2) Lower the rear roll centre.

3) Reduce the rear anti-roll bar stiffness

If the answer was no then the below solutions should be applied to your car:

1) Increase rear toe in

2) Reduce rear ride height

3) Reduce rear damper compression stiffness

4) Check tyre pressures with a gauge to ensure that the tyres are operating within recommended hot temperatures. Increase or decrease pressures accordingly.

5) Check tyre temperatures with a tyre pyrometer and make sure that the temperatures are distributed by less than 30 degrees Celsius between edges with the inside being the hottest. If the inside is too hot then increase positive camber. If the outside is too hot then increase negative camber.

Mid Corner

With the oversteer being identified as occurring in the mid corner section, the first question to ask yourself is, are you going through the corner at high speed or mid to low speed? If the answer is high speed then one of the below solutions can be applied to reduce the oversteer:

1) Increase rear damper rebound stiffness

2) Increase rear aero downforce (this will sacrifice straight line speed)

3) Soften rear anti roll bar slightly

If your answer was mid to low speed then you must ask yourself another question, does the car bottom out? If the answer is yes then you can apply one of the below options:

1) Increase rear coil spring rate.

2) Increase rear ride height

If the answer is no then you must ask yourself another question, does the rear of the car roll excessively? If the answer is yes then one of the below options can be altered:

1) Increase rear coil spring rate.

2) Increase rear anti-roll bar stiffness

3) Raise rear roll centre

If the answer once again is no, then the following solutions can be used to reduce oversteer:

1) Soften rear anti-roll bar stiffness

2) Soften rear coil spring rate

3) Reduce rear ride height

4) Lower rear roll centre

5) Check tyre pressures with a gauge to ensure that the tyres are operating within recommended hot temperatures. Increase or decrease pressures accordingly.

6) Check tyre temperatures with a tyre pyrometer and make sure that the temperatures are distributed by less than 30 degrees Celsius between edges with the inside being the hottest. If the inside is too hot then increase positive camber. If the outside is too hot then increase negative camber.

Corner Exit

If you have oversteer occurring in the corner exit section then there are no questions to ask yourself and one of the following solutions can be applied to reduce the oversteer:

1) Reduce rear ride height

2) Soften rear coil spring rate to allow the rear to squat slightly more on initial power application

3) Reduce anti squat geometry to allow the rear to squat on power

4) Reduce rear damper compression stiffness

5) Ensure there is no excessive droop in the rear suspension causing the inside rear tyre to lose traction.

The above solutions should be able to heavily reduce any understeer and over steer problems out on circuit, if not totally remove it. As always these alterations are pointless if the reasons behind the under/oversteer is due to driving style and being too aggressive for the conditions, circuit or tyres chosen etc. Therefore, make sure to improve and monitor driving style and fluidity of driver input carefully to ensure the best line, steering inputs and throttle/brake applications are being applied.

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1 Comment

  1. Excellent Article. Very insightful. thanks.

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