[200q20v] V8 vs old S4(tramlining)
DPulvino at agraus.com
Sun Mar 4 17:20:17 EST 2001
In reference to the tramlining issues, have the same situation on my car. As mentioned in a previous question I recently replaced more or less all of the suspension consumables short of the ball joints. I've searched the archives on this site concerning alignments and while I have not found a set of numbers that work best yet, I have found numerous people saying that an alignment not on the money can make a world of difference. I haven't gotten a chance to put the car up on jack stands yet and look for possible ball joint play, but as said previous, didn't specifiaclly note it as a problem when the car was apart.
So, I've also started doing some research on alignments otherwise. So far what I've seen has said that toe effects stability (only straight line stability was mentioned) and turn in response, and is a compromise situation; sharper turn in=decreased stability. Sharper turn in is acheived with a toe-out postion, and vice versa. Another factor in toe is dynamic toe, were the suspension components move as force is applied. So static toe needs to be set so that the toe while under motion is at an appropriate angle, taken into factor a median speed. As somebody else has previously mentioned, camber is important at least to keep the contact patch of the tire parallel to the road surface in cornering situations, compensating for sidewall/tire movement, and body roll, and possibly suspension compliance if that's as present; I also have not seen anything stating the camber effects straight line stability. Caster is another trade off situation, were high speed stability and steering effort are balanced, this however is not readily adjustable on our vehicles, unless some subframe movement counts. Of course the factory engineers have done their homework, so the going wisdom is a "the numbers as prescribed are derived with all of these factors in mind, and are therefore the best setup for the car" kind of thing.
What I have experienced on my car is tramlining, as well as a need to "saw" through corners. With the assumption that a positve toe number means toe out I've noticed that the last alignment on my car has the car setup at the extreme of the toe setting, on the verge of too much toe out. Camber is uneven between the sides, but within spec, and caster falls in the same category. At this point, I'll probably wind up taking the car back to the alignment shop to work towards correcting these issues. My idea at this stage is to get the toe slightly negative (slight toe in), even up the camber, and see if subframe movement can equalize the side to side caster. I'll keep people posted on things as they develop. I don't even want to think about steering rack or steering damper problems at this time; frustrating to have done all this work and not have the car substantially better, if anything, it's about the same as before-brake shimmy is gone though...
While going on responses so far I'll guess the answer is probably no, but does anyone have a set of numbers that work really well for alignment setups on our cars, or tolerances. (kind of funny, after saying how the factory has come up with the proper numbers to ask this question)
More information about the 200q20v