Oversteer vs. Understeer...Explained.

[PewterBird]

For some reason I have had trouble wrapping my mind around this. This explaination really helped.
Possible Sticky?

<a href="http://platz.com/pca/germany/blatt/Blatt%208.htm" target="_blank">UNDERSTEER / OVERSTEER TUNING

By STEF SCHEEPERS</a>

UNDERSTEER / OVERSTEER TUNING

By STEF SCHEEPERS

If you have to ask "what is understeer / oversteer?", it’s quite simple: if you approach a fast bend in the road, turn the wheel, but the car just plough straight on into a ditch, then you suffer from understeer. If you leave the same bend spinning backwards into the ditch, then you suffer from oversteer. Of course oversteer can easily be provoked when there is an idiot at the wheel, so don’t always blame the car.

For those of you who understand your car’s dynamics well enough not to make the typical beginner’s mistakes that will upset the handling, here is a list of changes that will guide you to tune your suspension to a neutral-steer for superior high-performance handling.

DECREASE UNDERSTEER..... CORRECTION.....DECREASE OVERSTEER

higher pressure........................tire pressure - front......................lower pressure

larger contact area....................tire section - front...............smaller contact area

more negative.........................wheel camber - front.......................more positive

softer............................................ springs - front.........................................stif fer

thinner (softer).............................sway bar - front.........................thicker (stiffer)

larger...........................................s poiler - front.......................................smalle r
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lower pressure.........................tire pressure - rear.....................higher pressure

smaller contact area.................tire section - rear..................larger contact area

more positive.........................wheel camber - rear......................more negative

stiffer........................................... .springs - rear.........................................softe r

thicker (stiffer).............................sway bar - rear.........................thinner (softer)

smaller..........................................s poiler - rear........................................larger

weight bias rearward................weight distribution..............weight bias forward

A few words of warning: if you are unsure about what you are doing, rather get help from an experienced person. Make your changes in small increments and first test the result in an open area where you can do little harm (like at one of our slaloms). Rather tune towards neutral-understeer, since an oversteering car is quite a dangerous beast that needs a fast hand to catch it. Have fun.

[V6Bob]

This is not awful, but I have at least two issues with it. They relate to the fact that it ain't this simple.

It makes it sound like changing the front bar and the rear bar would do similar things to the balance. On a race car with a-arms front and rear, that's close to true. On a car with a-arms in the front and a live axle in the rear changing the front bar doesn't affect the balance nearly as much as changing the rear bar, because a bigger front bar improves the camber of the front wheels. On a car with McPherson struts up front (3rd gen) the front bar changes the balance even less, because the camber curve of McPherson struts is so lousy.

It also makes it sound like oversteer is bad only because the driver has to be sharper. A common beginners error. Oversteer is also bad because it's slow, because the rear wheels need to have excess traction available to accelerate the car off the corner.

The stuff about the effects of tire pressure is also not great. Once again, it's a lot more complicated than this implies. Increasing rear tire pressure may make the car oversteer less to a point, but it will make the car oversteer more if you go too far, which is easy to do.

If this was a sticky it would need to be labeled as basic stuff, with the warning that, in reality, there are additional complications, and things may not go the way this says. Basically, it takes a lot more than this to really understand suspension.

[Dominic]

Exactly V6Bob... There is an awful lot that determines oversteer/understeer, and the tendency for a car to do such a thing.

Understeer is often encountered by inexperienced drivers when they first autocross simply because they enter turns too quickly and "demand" too much from the front tires... While this is understeer, this would happen in ANY car regardless of how it's setup.

Understeer/Oversteer can only be "felt" by the driver and seen by onlookers when the car is doing the same turn over and over at the same speed.

Essentially, understeer means you need the car to turn in quicker into a corner and maintain the speed it's going, and instead the front won't comply. Oversteer is entirely different, where the front complies but the rear steps out - and even though it is fun to a point, it is dangerous and it's slow too.

There is an maximum speed on every given corner for your car where neither the front nor the rear's cornering capability is exceeded. The trick in suspension balancing is to make the front give way at the same time as the rear, or slightly before, so that there is minimal push to let you know where your limits are [img]smile.gif[/img] . Nobody is perfect, watch F1 sometime and see.

There are a LOT of factors to balancing a car, but I think the biggest factor is the driver [img]smile.gif[/img]