I did some analysis on a couple of the pictures the photographer took of my car last time and found something interesting. Apparently, the front torsion arms are deflecting pretty significantly during hard cornering, enough that the loaded wheel (outer one in a turn) is going a few degrees into positive camber. I've read about this before, but I was a little surprised to actually see it show up that much.
In the pictures you can see the green horizontal-ish line through the headlight grill bolts, and then a line in green showing the axis of the wheel. The line through the headlights gives a reference to the chassis of the car to account for body roll in the turn, the picture not being level, etc. The yellow lines are at 90-degrees (zero camber) to the chassis reference lines. I measured the angle between the chassis lines and wheel axis lines and found about 2.5-degrees positive camber in one picture and over 3.5-degrees positive camber in the other! Static front camber on my car is about 0.5-degrees positive, but I'm running a few degrees of caster, so if anything the camber of the outer wheel should have been at least slightly negative.
In hindsight, this probably isn't that surprising. These cars were designed to run skinny bias-ply tires and only make 30-some-odd hp. They were probably lucky to pull half a G in a corner. I was pulling about 1 G or more, so I'm putting more than double the load on the suspension as it was designed for. Also, the cars were designed to favor understeer at the limit, so even if the VW engineers knew there was some deflection in those arms it was okay because it would favor understeer. The 40/60 weight distribution and swingaxle rear suspension made the cars naturally prone to oversteer, so they did everything they could to make the cars more likely to understeer (front sway bar, positive front camber, possibly built-in torsion arm deflection, and on later cars softer rear torsion bars and eventually rear Z-bars).
I plan to buy a spare set of front torsion arms and weld bracing to them to try and stiffen them up in the future. But first will come the offset bushings to at least get some static negative front camber. I may throw another pair of caster shims on it too to get some more camber while turning.
Attachment:
Capture8-analysis.png [ 1.17 MiB | Viewed 161 times ]
Attachment:
Capture6-analysis.png [ 1.18 MiB | Viewed 183 times ]