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3 minute(s) of a 612 minute read
8-7-2013
Steve, 2 separate issues here, and let me handle the easy one first.
When there are bumps and dips, all bets are off. This is the compliance I mentioned earlier, and in fact here the softer more comfortable car like the Turbo will be better than for example, a stiff car designed for the track like a GT3. A stiff car does best when the surface is smooth, the smoother the surface, the more a GT3 will gain on the Turbo. And vice versa, when roads are not smooth, a stiff car like GT3 will go airborne much more readily than a soft car, and Turbo will win.
The loosey goosey sensation on a smooth surface or the rear shake when accelerating out of corner, is a different issue. The stock Turbo does have soft rear end and a lot of twitchy motion and GMG has a video on their web site somewhere of the Turbo's rear end at speed and you could actually see it mamboing around the track with a lot of vertical and lateral motions. IMHO, this looseness *is* from the soft tuning of Turbo's suspension and will be reduced by stiffer spring or coilover, etc., stiffer sway bar like GMG or H&R, or stiffer links such as Tarett drop link, or rear toe link that replace stock rubber/plastic bushing with metallic heim joints.
There is another kind of looseness, that just very few (not all) people have mentioned with some lowering springs. This looseness is an undulating, floating, porpoise like motion, and it could be from a system that is underdamped. Meaning, stock shock doesn't have enough damping force to control springs.
8-8-2013
Just to add to the other (correct) answers already given. The anti-roll bar serves two functions, one is obvious from the name, the other not often discussed but equally important:
A. Anti roll
B. Adjust understeer/oversteer
A is just that, the anti roll bar adds roll stiffness and prevents your car from leaning in corners. Roll stiffness is very important because it keeps the tires in best contact with the road and maximize traction (larger contact patch) in corner. More body roll also unsettles driver and conversely, less body roll subjectively is a major reason for a car feeling "good." You've hear the oft mentioned expression "cornered as if on rail."
B is related to the effect of sway bar on roll couple distribution, an all important concept in understanding car behavior in corners. It has to do with the relative roll and ride stiffnes of the front of the car to the rear of the car, and how this would cause the car to understeer or oversteer. Adjustment of sway bars is used by professional drivers to affect understeer/oversteer behavior of a car. If you stiffen the front, you have understeer; if you stiffen the rear, you have oversteer.
To reduce the inherent understeer/neutral steer of a 4WD car, for a street car, I've found soft or med front and med rear to be a good compromise for the GMG bar, but of course this is strictly personal preference, no right or wrong and depends on the rest of the components in any particular car.
