suspension questions

[lauschie]

gday guys,

what is the job of a front and rear sway bar?? secondly, what is meant by oversteer and understeer?? has anyone here replaced their sway bars and did it improve steering and handling?? what sway bars did u use to replace original?? how much did they cost including labour??

all the best,

lauschie

[CAP]

Oversteer is when the rear end of the car slides out when cornering, so in effect the car has oversteered and has now turned too far into the direction of the corner, these days alot of people refer to this as drifting.

It happens when the lateral forces on the rear of the car and/or engine power overcomes the grip of the rear tyres.

Understeer is when the front of the car either slides out or simply drifts too wide when cornering, so in effect the car has not turned enough or understeered into the corner.

Typically a RWD car will have a tendancy to oversteer as most of the weight is on the front end of the car and the power is going to the rear of the car which is lighter.

A FWD car will have a tendancy to understeer as even more weight is on the front of the car, no power is going to the rear.

But with the ideal suspension set up, the amount that a car does these things can be reduced or eliminated. The Corolla for example is a predominant understeerer. The standard springs and sway bars are soft which make the car body roll when cornering. The tendancy for the car body to roll in corners, means that the car's weight is always shifted to the outside tyres (particularly the front outside) and then that 1 tyre needs to handle the weight of the car mid-corner and of course it can't, so the car will understeer. If you reduce the body roll, you reduce the amount of weight that 1 tyre caries, distribute more to the other 3 and in turn reduce understeer.

Reducing ride height reduces body roll a little, you're bringing the car close to the ground and lowering the centre of gravity, the same way to can balance better with your knees bent, so shorter stiffer springs improve this.

Installing more solid, stiffer sway bars also reduce body roll, because they control the amount of flex in the chassis and stiffer bars will reduce the amount of flex and roll.

Hope this all makes sense.

Edited July 10, 2006 by IZZ-FE

[SuperDave]

Front and rear anti-roll bars (sway bars) basically reduce the amount of roll the car has when cornering. In doing so they reduce the amount of spring and dampening rate required since they don't need to then perform a secondary function of controlling the roll. The anti-roll bars can also control the balance of the car, ie oversteer or understeer.

Oversteer is when the backend starts coming out and trying to overtake the front of the car. Best example of this is drifting, but they do it with control. Understeer is when the car enters the corner and in the most extreme case just goes straight on. Best example is a frontwheel drive car entering a corner far too quickly.

If you want more understeer, increase the front ant-roll bar or decrease the rear anti-roll bar.

If you want more oversteer, decrease the front anti-roll bar or increase the rear ant-roll bar.

My dad has a Whiteline rear anti-roll bar on his Corolla and it is pretty good. Handles a lot better and doesn't roll as much. TRD make one which is slightly stiffer. To install the rear don't bother paying someone to do it unless you don't have the tools. Takes all of 5 minutes to do. The front anti-roll bar is a little more complex to install however. Again check out the group buy threads for a rough price