Understeer vs oversteer

You can use the throttle foot to control oversteer and drive the car through its imbalance.

All you can do with a understeering car is slow down for/in the corners.

 

It depends on the driver. Alonso prefers a car that understeers more, whilst Schumacher prefers oversteer (he places the car using the throttle). Both are horrendously quick. You tell me.

In (single seater) simulation games I set my car up with a little bit of understeer in mind for turn in, but after the apex I prefer oversteer. Others try my setup and are ****ty with it, and I'm ****ty with their setup sometimes.

totally depends on how you drive.

In a road car, oversteer is the most fun though, and I don't care about being superfast...

 

Driver preference aside, it also depends on the car (downforce/mechanical grip, weight balance, power, etc) and track (slow/fast corners, level of grip, etc.). If you have plenty of power and mechanical grip you may prefer oversteer to throttle control. If the car is underpowered (compared to corner speed) you most likely want slight understeer since you won't be able to help yourself if the rear end snaps.

In my personal experience I preferred slight understeer in open wheel cars (F3) and slight oversteer in closed cars.

 

Also depends on the track....

Speedway or oval - set up for understeer. If you lose traction at the front, you can breath off the throttle, transfer a little weight to the front and stay in the groove. An oversteering car in this environment can be lethal, because generally by the time you catch it your front wheels are pointing at the wall and that is where you end up. Feet, meet wall, wall feet....Hello Dr Trammell.

Road Course with medium and lower speed corners - set up for slight oversteer. As the car breaks free at the rear, a gentle application of throttle transfers a little weight to the rear and catches the slide. Having allowed the car to rotate in this manner results in less steering input and a faster overall lap.

Engineers like understeer even though it is a little slower because the car is more likely to come back in one piece. It is for this reason that with a new driver, the car is set up for understeer. Throughout the day, you can give more adhesion at the front (springs, wing, sway bar and tire pressures) and your driver will get faster.

 

I remember reading an interview with Jackie Stewart early in his F1 career. His said that his preference was for slight understeer.

 

Also note: a car setup for very slight understeer in slow corners will drift over to slight oversteer in faster corners a) under power inducement, b) under aerodynamic effects.

 

I've always preferred just a bit of oversteer in my set-ups.

Can't recall where I got this one:
Understeer = hitting the wall with the front of the car..
Oversteer = hitting the wall with the rear of the car..
Horsepower = how fast you hit the wall..
Torque = how much of the wall you take with you.

 

Good explanation. You can generally "trim a car out" and reduce rear downforce to equalize the balance.

I agree on the oversteer. Makes the car do more of the work turning.

However, torque is how far you MOVE the wall when you hit it.

Seriously, car balance is primarily affected by driver input amplitude and timing. Most pros have pretty big confidence and tend to charge corners more than amateurs. What the car does when that happens is pivotal in the driver's continued success or failure to negotiate the corner.

It's been proven that whatever setup produces the desired behavior for the driver enhances their confidence, hence reduces the "hang time" or pausing of control inputs and they get through the corners quicker. Balance is elusive at the limit, however. It's like being on a knife edge and sometimes difficult to replicate consistently, although that's what they'd all like to do.

 

Assuming we are talking about rear wheel drive cars, very small amount of understeer is faster. The reason is that it allows you to used more power coming off of corners and provides faster corner exit speed and faster speed down the straights. If the car is loose you can't apply power until you are a lot straighter. As Alan Johnson says in his book, "road races are won and lost on the straights".

The lower power the car has the closer to balanced you want it.

Oversteer is slow for a lot of other reasons, the above being the most critical. Another reason is that oversteer requires the car to be turning before it develops lateral acceleration. The result is that the transient response of an oversteering car is slower than an understeering car. Another reason is that as the speed of the corner increases a rwd car will oversteer more. This is because the higher the speed the of the corner the greater the amount of power is required to maintain speed and more that tends to make the car oversteer. If you have low or medium speed oversteer you are going to be really loose at high speed.

Bottom line is a bit of understeer is faster. Never mind what you prefer, if you want to go fast learn to master the physics and make it work for you.

 

Actually, if its under steering out of a corner, you have to stay off the gas until you are pointed down the straight, as that takes even more weight off the front, making the understeer worse. When I drive a kart with a non symmetrical setup, that pushes really bad in the left handers, I'm keeping off the gas pretty much until I'm aimed down the straight, trying to get as much weight over the front so it corners better. With a better balance, I could get on the gas sooner, and have more speed down that straight. In this case, I consider a slight disadvantage in one cornering direction - massive understeer in lefts, to be made up for by slight over steer in rights. All track dependent of course. But when I'm driving out of a corner, and there isn't enough grip at the front, getting on the gas makes it worse, if there isn't enough at the rear, mild throttle helps balance it out.

Lots of people reference Schumacher, you look at the data of his right foot, he likes to be on the gas early, much much earlier than his competitors, and his right foot isn't an on/off switch, he's doing lots of little partial throttle tweaks long before he gets out of the corner and goes flat out.

 

From what I know / learned - understeer in road cars - even on the track is a bit preferable & safer, it gives you a margin.

Oversteer on race cars - alows you to carry more speed into the corner, but you have to "cathch" it on the way out or else you'll spin. Aero not included. Schumacher is carrying lots of speed thru corners and wants that instant rotation / turn that oversteer helps with.

Classic F-1 cars - 60's - 90's had a bit of Understeer in them... aero was not as sensitive and balance not as completely crucial as today. Stewart's comment goes along with his maxim of never accelerate when you know you'll have to immediatley come off & hit the brakes.... he was all about smooth / balanced driving. Today with the huge g forces - not much is smooth and fluid anymore, but Schumacher is simply the expert at rotating the car, saving brakes and letting the car do the work... and he has the physical strength to cope with it.

 

Oversteer: scares passengers
Understeer: scares drivers

 

Yepper and I prefer oversteer.

 

Given the freedom to design your own suspension A-arms and chassis pickup points, one can design a suspension to create a tiny amount of understeer as weight is transfered to the rear wheels under thrust.

 

Have not found that to be true.

If you want to go fast, you need to be able to trust that the car will follow your directions as SOON as you tell it to do.

You need the confidence to release brakes at a higher speed, get the car pointed as soon and in as short a time and distance possible and you need to commit to throttle application BEFORE it's clear that you'll make it out of the corner!

 

Same can be done with existing ULA, SLA or coil-over strut-type suspensions with spring rate changes.

 

An oversteering car has SLOWER transient response than an understeering car. I know that doesn't seem right, it feels to the driver that a car that oversteers responds quicker, but that is simply driver perception.

You have to think about it for a moment. An understeering car builds lateral g as soon as you turn the wheel, since front tire slip change is directly related to steering angle change.

An oversteering car has to yaw first and this increasing yaw angle increases rear wheel slip angle, and THEN the car builds lateral g. As a result, the transient response of an understeering car is actually faster than an oversteering car. What most drivers are feeling on turn in with an oversteering car is actually yaw overshoot. It overcomes the driver input and the car is rotating so it "feels" like it is responding quicker. Actually it is not.

This is somewhat akin to drivers that stab in steering lock to "set" the car. We've all had students who do that thinking it makes them faster. This builds a lot of yaw angle and gets the car rotating, which makes the driver comfortable that the car is going to turn, but that jab at the wheel really only upsets the car and requires that he slows down more on corner entry before he puts that higher initial steering input into the car.

A common response to a driver saying that the car isn't turning in quickly is to add some toe out to the front end. Front end toe out increases transient understeer and improves the transient response. The driver feels that the car is responding faster with the toe out because it is.

Please don't confuse and assume that I'm saying you want the car to push. I'm just saying that the balance should be just a bit on the understeer side of netural. You want the car to have a lot of front end bite, but the back end to follow you and not be stepping out. The driver should be able to feel that the front tires are working just a bit harder, but not so much more that you are abusing the front tires. In that case the car just goes anywhere he points it with the wheel, and it does it quickly. If he is a bit too hot, he can lift and get the front end to hook back up. The car going exactly where it is pointed, builds a lot of driver confidence and that's important too.