How to reduce understeer by adjusting spring rate and anti-roll bar stiffness

"I just had a great time understeering around that track in the wet" - said no one ever.

lotus elise drift
This guy is loving life.

Although both understeer and oversteer are undesirable if your objective is to drive as quickly as possible, at least one of them can provide hours of fun and entertainment (hint: it's not understeer).

In this article we will briefly discuss what understeer is and then cover some of the modifications which can be made to your car's suspension to reduce understeer.

What is understeer?

Understeer occurs when the front wheels lose traction whilst cornering whilst the rear wheels still have traction, causing the car to take a wider route than intended around the corner. This is often experienced by every day motorists as heading towards a hedge on the outside of a corner you do not want to head towards.

Most cases of understeer are caused by one or more of the following:
  • Applying too much throttle too early in the corner
  • Braking whilst entering the corner
  • Simply taking the corner too fast
  • Road conditions reducing traction e.g. ice/oil/diesel/mud/water
Clearly by the laws of physics you can not eliminate the above causes through modifications to the car, however there are many suspension adjustments which can be made to alter the understeer/oversteer behaviours of a car during different stages of a corner: corner entry, mid corner and corner exit.

How to reduce understeer

Reducing understeer by adjusting spring rate

  • Increase rear spring rate - this will increase the rear roll resistance which will reduce understeer but increase oversteer.
  • Decrease front spring rate - this will decrease the front roll resistance which will reduce understeer but increase oversteer.

Reducing understeer by adjusting the anti-roll bar (ARB)

  • Decrease front anti-roll bar stiffness - decreasing roll resistance at the front which will reduce understeer but increase oversteer. However, too much body roll could reduce tire contact patch size, increasing understeer.
  • Increase rear anti-roll bar stiffness - increasing roll resistance at the rear which will increase oversteer but reduce understeer. This may also reduce wheel camber change on cars with independent rear suspension, maintaining a larger contact patch whilst cornering and reducing oversteer.

As you can see, almost every change made to a vehicle's suspension will have more than one consequence so getting the balance right between understeer/oversteer/ride compliance/tyre wear/ and a million other variables requires expert knowledge and years of experience.

For the best results to suit your requirements, we would always recommend consulting a professional before putting your hand in your pocket to buy new parts.

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