I’ve heard these terms as long as I’ve been reading about cars, and I vaguely understand that they refer to the tracking tendencies of front or rear end during turns. But I really don’t know what the heck they mean? Can anyone explain. And when are they considered good and when considered bad?
Understeer means the front wheels are losing traction first(NASCAR will call this “tight”)
Oversteer means the rear wheels are losing traction first(NASCAR will call this “loose”)
Understeer is desired in most street driven cars because it “feels” safer and is easier to correct if you are a novice. The car just stops turning and scrubs off speed quickly. Oversteer can scare the shit out of you if you are not ready for it. But any car can do either if provoked properly.
Understeer: You turn the steering wheel and the car keeps going straight ahead. (extreme example).
Oversteer: You turn the steering wheel and the back of the car slides out (like a rally car or speedway car)
I had heard the definition back in the Grand Prix days of my youth as:
Understeer: The front tires track on a line outside of their respective rear tires’ path. (I.e. left and right.)
Oversteer: The front tires track on a line inside of their respective rear tires’ path.
Certainly, classic “oversteer” is what we perceive as being the obvious display of good driving ability.
But beware - perception isn’t everything! I once had the pleasure of having a real good chin wag with former F1 World Champion Alan Jones - he happens to live in my home town. I recall talking to him about the classic 1981 Monaco Grand Prix where he was hanging the arse out of his Williams lap after lap after lap trying to pass Gilles Villeneueve in the final 20 laps for the race win. It was a race which has gone into legend as one where Villeneuve in his sub standard Ferrari held off the obviously faster Jones and his all conquering Williams… and yet, in Alan’s own words…
"Oh sure, it looked exciting all right… but let me tell you… everytime that back end kicked out on me in that race that was another 10 yards Gilles pulled away from me… you see… all things being equal, you actually want to setup a Grand Prix car to deliberately understeer just a little bit - not too much - just a bit. Then, in theory, you can drive it with the throttle in lovely controlled 4 wheel drifts all the time. But when your back end kicks out, your car’s forward speed actually drops believe it or not - but with understeer, at least your forward speed tends to stay much the same. The problem with the Williams was that it was SUCH a well setup car, I tended to make the back end loose on purpose so I could drive it with the throttle, but in that Monaco race, I totally cooked the rear tyres with 10 laps to go and I simply wasn’t getting any power to the ground. It sure made Villeneuve’s reputation though! It looked as though I was throwing every thing I had in the car at him - when in reality, I was desperately just trying to save the tyres and keep up with him. I probably had a quicker lap up my sleeve if I could have got past, but it’s Monaco… it’s impossible to pass there unless someone makes a mistake. "
General concept in layman’s terms:
Understeer–the car changes direction less than intended.
Oversteer–the car changes direction more than intended.
Heh, more graphic layman’s terms:
Understeer – front end of the car hits the wall first
Oversteer – rear end of the car hits the wall first
If you want a subjective opinion about two very normal cars, I can give you one. I had this '77 Rabbit that was just a little bat out of hell (I unscrewed the restrictor bolt from under the gas pedal, and it actually made a difference). It was FWD, but very neutral in handling. When I took a good turn too fast, the inside rear wheel would actually lift off the ground. I think this actually helped load the front wheels when cornering. Nevertheless, it was extremely disconcerting to feel yourself drifting outside of the radius of the turn, and there’s not much you can do about it once you’re committed to the corner. As you can see here, this guy has his ass all up in the air, but he’s still pulling through the turn.
Now I drive a little Miata. Realistically, it’s very similar to the Rabbit–maybe a touch slower, actually. It’s also a very neutral car, but when pressed it starts to drift, and then the back end starts to slide out. When it begins to oversteer, it’s very predictable and correctable, and fun as hell. As you can sort of see here, this guy is beginning to turn in the direction of his slide in order to correct, and he’s actually doing some of his steering by pushing out the back end as he goes through the turn.
My opinion is that the Miata is much more fun and probably safer, but that if I could race myself my old Rat could probably smoke the Miata in turns because the envelope can be more easily approached in the FWD car. However, as racekarl pointed out, push either one of them too far and you’re going to go into the wall.
Or the ditch, which is where the Rabbit eventually wound up. Please drive responsibly.
It’s pretty difficult to get a late model US market front wheel drive vehicle to oversteer under normal driving conditions.
Even among the few available late model US market rear wheel drive cars, oversteer is generally uncommon without trying really hard. Liability, you know. That Corvair thing comes to mind.
I beg to differ. I put a buddy’s '91 (that still count as late model? If not, feel free to ignore this post) Accord into a hedge by oversteering. Actually, I was speeding aroung a coner, understeering, hit the brakes, and the rear snapped right around. Not really “normal” driving conditions, but not too extreme either.
Ender_Will, what you describe is a special category called ‘throttle off oversteer’. By lifting off the throttle, or worse yet hitting the brakes, weight transfers to the front which causes the front to regain traction and the rear to lose it.
I got some oversteer once in a front wheel drive car on a wet road. I was going thru a corner with a steady throttle and the back end jumped out about a foot. It was easy to catch, but I think it freaked out the driver coming the other way!
I currently have a rear wheel drive car but they design in understeer by putting narrower tyres on the front.
Thanks to everyone who replied.
I am going to continue flaunting my ignorance by asking: does the type of under or oversteer change depending on whether the vehicle is frontwheel drive, backwheel drive or four wheel drive?
The drive wheels should not make a difference in how a car is biased towards understeer/oversteer except for when the car looses traction because of too much power to the wheels. Usually with RWD sports cars too much power to the back wheels in a turn can cause them to break traction and cause an oversteer condition. To much power too the front wheels could cause them to break traction and result in understeer. This is different from understeer/oversteer caused by the cars nautural bias or weight distribution.
As kferr mentioned a car can change from understeer to oversteer depending on weight distribution. If a car has a slight bias towards understeer and you are in an understeer situation, lifting the throttle will put more weight on the front tires and change the bias towards nuetral (four wheel drift 
) or oversteer . However if you panic and lift off the throttle completly (or worse hit the brakes), you can get massive oversteer because of the transfer of weight to the front wheels :eek: . A manual transmission makes it much easier to control this when driving near the limits, not that I would ever do that
I think most modern cars are heavily biased towards understeer because that is safest for an inexperienced driver or when the driver panics and hits the brakes. However you can change a cars natural bias somewhat by adding or increasing the size of swaybars and other modifications.
Well, the way you’ve worded this makes it hard to answer. This is gonna be long, so bear with me
There is only 1 “type” each of oversteer or understeer; in a sense, either the car is tracking where you want it to go, or it isn’t.
To answer what I think you’re asking, given identical, neutral balanced suspension designs, and similar weight distribution, a front drive car will tend to understeer, a rear drive car will tend to oversteer, and an AWD car will remain neutral or understeer.
To help illustrate this point, there is a graphic device driving instructors use called a traction circle. Imagine graphing the performance of your tires on an X,Y coordinate plane. Up repersents acceleration force, down represents braking force, left and right are turning forces in each direction. The unit of measure on the diagram is G force. Now draw a circle centered on the origin, with a radius of 1 G. A passenger car tire is generally capable of gripping the road with 1G of force, after which it losses traction and begins sliding. You can see from this circle, that as you mix two axes of force, you lose maximum force along any one axis. What this means is that if you ask your tires to do two things at once (say, acceleration and turning) you will get less than maximum performance for each job.
So that means that on a front drive car, the front wheels are asked to get the acceleration force to the ground, leaving less traction available for turning (front tires having less traction than rear tires = understeer). On a RWD car, the situation is reversed.
However, nearly every passenger car sold in the US is designed to understeer, regardless of the type of drivetrain. In actual practice, this has little effect on your driving, it just means that the manufactures have to take different measures in tuning the suspension of the car to ensure that it will understeer.
Thanks. You answered the question I should have asked.