[Lexique de la voiture ancienne] #17 under and over control

“Reassuring understeer behavior. This is a phrase I’ve used many times in my essays (see there). Except that driving an old one doesn’t necessarily reveal what understeer is and what’s conversely oversteer. So we’ll explain it all to you.

The context

We are talking to you here about “extreme” phenomena, which do not occur in all situations, and which are really risky, as they can lead to you leaving the road, spinning or even getting into an accident with another vehicle.

Let’s start with the understeer. It is the extension of the tractor. In fact, the car does not turn enough and approaches the outside of the corner. Some cars are more affected than others, we’ll get into the details right after. Most of the time it’s generated by going into a corner at too high a speed, and the front wheels, the steering, don’t have enough grip to direct the car’s mass in the right direction.

Then the override. It is the opposite. This time the old or modern car will turn too much. For once the problem does not come from the front wheels but from the rear wheels, which do not have enough grip to “follow the path of the front wheels” and go outwards. The car’s axis changes and aims inward, and there are two scenarios in the end: a spin or an exit, but inside the turn this time.

Causes and solutions:

The undermanagement:

This has become more and more common on cars over time. Why ? Because traction has been democratized, to the detriment of propulsion, and understeer is a phenomenon especially encountered on traction.

The reason ?
When we talk about going too fast into a corner, we are talking about two types of architecture, traction and propulsion. The track is widened because the grip in the steering gear, the front, is not sufficient. Also, a loss of grip due to gravel or water will have the same effect!

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On the other hand, another excess of optimism, the understeer can also be triggered by a slip of the front wheels when you apply the gas too early in a corner. In fact, its grip is slipping and we are going into understeer. And it only affects pull-ups.

The solution?
If you ever experience understeer, the ideal is to always ease off the throttle to reduce your speed and steer harder to get the car turning. Be careful when braking: on a car without ABS, you can lock the wheels and cause the same loss of grip as a skid. You can also try to put the wheels a little more on the axis of the car to give them grip, but only do it at the beginning of understeer or you will widen the track even more.


This is the risk found in many means of propulsion. In the world of old cars, it inevitably affects many cars. This is particularly pronounced on cars with a rear engine (and not a mid-engine), and unlike understeer, it can also be provoked to gain efficiency in certain cases. When it goes wrong, there are two outcomes: either the oversteer takes you off the road on the inside of the turn, or you spin (when the rear end continues to push too hard).

Le Mans Classic 2022 Plateau 4 Jour 2- faux convertible

The reason ?
For a car to turn, it must move forward, logically, and the front end must be in the right direction. To move forward, you need power going to the rear wheels. And it’s your right foot that controls it. The main cause of oversteer is when you give too much gas or too early in the turn. The rear axle will then lose grip and will no longer be able to counteract the centrifugal force. It will widen the track, go outwards when the front axle will always aim inwards! Your car will aim too much on the inside of the turn.

Note that without going over the throttle too early, you can also initiate oversteer if you enter a corner at too high a speed. This is the case on “all-in-the-rear” cars. The mass on the rear axle is significant and this mass is even more subject to centrifugal force. With poor rear traction (in the rain), and on board an Alpine A110 or even a Cox, you will have the rear end which will very logically extend its path and create oversteer.

The solution?
Don’t slow down! Especially not. And don’t let up on the gas. The ideal is to even hold a sprinkling of gas so that the front axle continues to push. At the same time, you counteract. Thus, the front of the car will aim less towards the interior.

When looking for override
As much as no one is looking for understeer, oversteer can be a good thing. In fact, when mastered, it allows you to keep control of the car. As a result, from the rope we can have the car on the axis to accelerate earlier. This is what many rally drivers are looking for, the same ones who do not hesitate to pull on the handbrake.

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Why is understeer more reassuring?

To return to my first sentence, I’ll stick with it: the understeer is more reassuring. An automatic understeer only widens a lane… and it’s easier to catch up! Plant the brakes (within a certain limit), steer harder, it won’t send you spinning! In addition, understeer is easier to detect and occurs less quickly than oversteer.

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