Understeer and Oversteer – Kart Handling

Oversteer and understeer are words used to describe the handling, or balance of your kart. If the back of the kart is sliding, it’s called oversteer. If the front tyres are sliding across the track, it is understeering.

If the kart is following the racing line nicely without sliding around, it is called neutral handling.

What is oversteer?

An extreme case of oversteer, leading to a spin.

A quick way to describe oversteer is to say that the rear tyres don’t have enough grip, so the back of the karts starts sliding.

Oversteer is often called sliding, and drifting is also a type of oversteer. Another term that you can use to say that your kart oversteers is to say that it is “loose.”

What causes oversteer?

A driver can do things with the throttle, brake, or steering to create oversteer.

When braking for a corner, if you brake too hard, the tires can lock-up, which means that they stop rolling along the track and skid across instead. When the tyres skid across, they lose almost all sideways grip, so the back starts to slide around (oversteer).

Overseer with the driver counter-steering in attempt to stop the kart from spinning.

How about on the corner exit? If a driver gets onto the throttle but isn’t able to start straightening the steering wheel, it can often create oversteer – this is even more likely in wet weather, because the rear tyres are more likely to have wheelspin because they have less grip. Wheelspin = tires spin faster than the kart is moving.

You might also create oversteer moments simply by steering very fast or aggressively. This moves a lot of load (weight) from side-to-side very suddenly, and it can overwhelm the tires.

Is Oversteer Good?

Big moments of oversteer are almost never good. They will slow you down because the kart is unlikely to be going where you want it to go, and the slide itself will slow the speed of the kart down the kart.

It also wears down and overheats your tires!

You shouldn’t be worried about small moments of oversteer though. Small slides are almost certain to happen when you are close to the limit and driving fast. Small means that somebody looking at your kart from the outside would not really be able to notice the sliding. It’s very subtle.

How do you control oversteer?

Steering into the slide is usually the fastest and best way to correct oversteer. If you are in a right-hand corner, and the kart starts to oversteer (the back of the kart sliding left), you should steer to the left for a quick moment until the kart stops oversteering.

In extreme cases of oversteer on corner exit, you could also ease off the throttle pedal.

How about braking? It should only be used as a last-resort. The reason is because when you brake, load (weight) move towards the front of the kart and away from the rear tyres. Removing load from the rear tyres also reduces the grip they are generating.

What is Understeer?

A common mistake for karting drivers is to think that “understeer” means they are not steering enough with the wheel. As mentioned above though, it’s a term to describe how the kart is handling, rather than what the driver is doing with the wheel.

In simple terms, it means that the front tyres are sliding across the track. You try to steer more, but the kart doesn’t want to take a tighter line, and instead keeps going almost straight-ahead.

Understeer – the driver wanted to take the green line, but because the front tyres didn’t have enough grip for the driven speed, the kart went off the track.
What causes understeer?

The most common cause is trying to enter a corner too fast. If you brake too late or not enough for a corner, the speed will be too fast for the tyres to cope. You can steer a lot, but because the speed is too high, the kart goes a lot more straight than you might want it to.

Another common reason is getting on the throttle too early. This creates understeer in two way:

First, it starts to increase the speed of the kart, and since the throttle was too early (likely way before the apex), the driver would need to start adding more steering input later during the exit of the corner, which the tyres simply can’t handle. You are asking the kart to go faster and corner tighter.

Second, it moves weight away from the front tires, and towards the back of the kart. This reduces the grip available at the front tyres.

How do you control understeer?

For our first common cause of understeer of entering a corner too fast, it not actually easy to do much. In a kart with only rear brakes, it does help to steer quick a lot, because it helps the front tires slow down the kart a little bit more – but other than that it’s a matter of waiting for the tyres to grip when the kart has slowed down enough. When they do grip, the driver needs to be ready to react, because it’s very likely that the kart will quickly snap from understeer to oversteer!

Corner exit understeer is easier to deal with – especially if you notice it early enough. Simple ease off the throttle pedal. This does two things = it helps put weight back onto the front tyres increasing their grip, and it also stops the kart from accelerating any more. Jumping off the throttle suddenly is also an option, but is usually overkill, and can result in sudden oversteer instead.

In the 2nd situation, braking is a very common mistake and something to watch out for. While braking can slow the kart down it also stops the kart from turning nicely. The technical reason for this is a bit too complicated to explain here, but keep it in mind and only use the brakes as a last resort to try to stop the kart from running off the track or hitting the barriers.

Is Understeer Good?

A little bit of understeer – especially early in the entry phase of a corner is actually good. This is because it’s predictable, and the alternative is oversteer – which is much more unpredictable, and also means you’re be steering in the wrong direction for the corner!

Just as with the good type of oversteer, this understeer should be almost impossible to see from the outside. If someone from the outside can tell that the front tires are obviously sliding across the track, it’s likely far too much understeer!

Conclusions

There is a lot more to kart handling than is covered here, such as load transfer that we discussed in class a little bit (weight moves forward when you brake, backwards when you accelerate).

These basics should give you a great start to understanding the more advanced handling aspects of karting. Make sure to think about these when you drive. Whenever you have oversteer or understeer moments, take a moment to think why they were happening once you’ve come back to the pits.

Happy karting!