Torque Arm for road racing
#21
You can also change instant center by changing the angle of the control arms
What a torque arm does is position the "instant center." The instant center is the vertical line that the car rotates at. Think of it like a see saw. if you move the pivot, you affect the way the see-saw transfers weight. Generally you want the pivot as close to the center of gravity as possible. This is the way the torque arm is set up at the factory. If you shorten your torque arm and your control arms point up toward the front of your car, less weight will be transferred to the rear axle on acceleration, maybe good, maybe bad, depending on lots of other factors. If your control arms are pointing down, and you use a shortened torque arm, more weight will be transferred to the rear axle on acceleration. So, you could just change the angle of your control arms to tune the traction in your rear end, instead of paying $500 + for a fancy torque arm. But the stiffened ones do work better. I am one of the few people in the world who drifts with a torque arm, and after trying every imaginable torque arm set up possible, I have found a factory length stiffened torque arm with the soft factory bushings is best. I actually run a brace through the back seat of my car connecting the front of the torque arm to the axle.
#23
It took me this long to figure out how a torque arm works. If you look on the internet, either the discussions are to general and vague or they are too technical. In my opinion, neither those in the technical nor the general discussions actually have a conceptual grip on how a torque arm works. And those who do know how it works, like the manufacturers are keeping their mouths shut so that people will buy their product whether they need it or not. There are still aspects to the torque arm I do not understand, but know from experience affect performance. For example, a harder t/a busing will give you less turn exit snap back than a softer bushing. Why? I have not a clue. I have run my car without any torque arm at all, and the car drifted fine, with only a negligible affect on performance, except that the car really wanted to understeer, again, why I do not know. I suppose if I ever have an oversteer problem (like a bent axle) I could remove the torque arm to offset the oversteer.