Originally Posted by
DG
Doesn't work - well, doesn't work as expected.
The thicker rear sway bar attempts to reduce grip on the rear by increasing the amount of rear weight transfer. Normally, that increases oversteer.
But AWD cars have a differential connecting the front and rear wheels. When you apply power, the differential "senses" (that's a gross oversimplification of a complex action but we can treat it this way) that the rear has less grip and routes the power forward - where it induces understeer.
However, that rear sway bar is still there, doing it's best to unstick the rear. So in instances where the differential isn't playing games, it induces oversteer.
What you wind up with is a car that, in the main, understeers, but every once and a while snap-oversteers with very little warning - and the more rear spring/bar you put in it, the worse it gets.
The 3S has a rear-torque-bias centre diff so the problem should be a little less prevalent, and indeed, the 3S will rotate a little with throttle before the understeer takes over. But any car that can sent large amounts of power forward will understeer.
I set up AWD race cars with just the slightest bit of spring/bar oversteer bias, so you can get the rear dancing on rapid transitions and lift throttle, and I prefer to do it with spring rather than bar (after a series of aftermarket rear bars, I eventually went back to a OEM rear bar) The 3S, with it's rear-torque-bias centre diff, probably needs even less rear spring.
The other issue here is that the 3S has McStruts on the front, so it has horrible (which is to say, very little) camber gain in roll. The way you normally combat this is to run a lot of front bar, and I expect that a good way to reduce understeer on a 3S is to thicken up the front bar a lot.
However, once you get to the point where you are lifting the inside front clear of the ground - normally the hot ticket on a car like an M3 or Mustang - that differential issue rears up. Lifting the inside front under power is going to cause all three diffs to go insane.
So on a 3S... well, the main issue with a 3S is "doctor, it hurts when I do this" so the solution is to "don't do that" and get a car with less Weird Harolds (like a C5 Corvette) for track use. But if you are bound and determined to use the 3S, the answer is probably more front bar, as the lack of camber gain in the front is the single largest problem. Quaife front diff, Quaife centre diff (assuming that doesn't remove the rear torque bias feature, which is pretty important) and leave the rear viscous.
Street car, larger front bar and be done with it.
DG
