Uneven tire wear
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From: Bird lover in Sharpsburg
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From: Boulder Creek, CA
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This happens to me too (inner wear of rear tires), but in my case it is because there is WAY too much camber and excessive rear wheel spin! 
My rear toe is dead nuts on, but because I can only get a minimum of 1.1° (or was it 1.3°) camber, I run both sides at that setting. Stock is a max of 0.8° IIRC.
I've just completed replacing the upper control arm bushings and the camber bushings and hope that will fix the issue. Still waiting on a part to put my TT back together before I can check anything.
My rear toe is dead nuts on, but because I can only get a minimum of 1.1° (or was it 1.3°) camber, I run both sides at that setting. Stock is a max of 0.8° IIRC.I've just completed replacing the upper control arm bushings and the camber bushings and hope that will fix the issue. Still waiting on a part to put my TT back together before I can check anything.
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Michael S. Palmer
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Was just in the garage putting on my winter tires. When I removed the tires I use for three season fun, I noticed the inside of the rears was wearing faster than the outside.
I had installed some red sport Boges that came with springs already installed (which I bought from Gary Knox, thanks Gary!), which I believe were from an S4 or maybe a GT.
I got a four-wheel alignment, but now I realize that I might have screwed up. With these newer springs and shocks, do I need to use a later cars alignment parameters or do I still use the 82 numbers?
Thanks for any help,
I had installed some red sport Boges that came with springs already installed (which I bought from Gary Knox, thanks Gary!), which I believe were from an S4 or maybe a GT.
I got a four-wheel alignment, but now I realize that I might have screwed up. With these newer springs and shocks, do I need to use a later cars alignment parameters or do I still use the 82 numbers?
Thanks for any help,
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From: Elmhurst, IL
Bummer is I just put on the snow tires, which do have the car riding a little higher.
Drifting
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From: New Canaan, CT
I had my alignment done on my 91 GT about 1500 miles ago and 1 year. I changes the shocks and had to get my alignment redone. Something to do with the way the rear shocks are mounted etc.
Bilal
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It's clear from your post you do not understand how the rear suspension works. The only aspect concerning the alignment the new rear shocks would affect would be ride height. Nothing else (at least on the 928).
The rear alignment on the 928 is controlled by a camber eccentric on the rear cross member and a toe eccentric on the leading mount for the weissach control arm (just behind the rear jack point). I have seen toe eccentrics go bad, and in theory the camber eccentrics can go bad too, but I have yet to see one on a 928. It seems the suspension bushings are prone to wear and deformation over time. In particular are the lower control arm to rear cross-member bushings (2), and the upper control arm bushings (4).
There are two other area I have seen that can cause problems for alignments. One possible area is the main pin that holds the rear hub, shock, and lower control arm together. If this pin is bent or warped, you may never get the alignments right. The other area is the section of the lower control arm from the rear cross member to the hub. This is the thin vertical piece of sheet metal (for lack of a better term) on the lower control arm. I have seem where tow trucks or dyno operators have strapped the car down and bent this rather flimsy piece of metal. Obviously if this is deformed, you may have issues getting the car aligned.
Getting back to Robot Bob's issue, it is hard to say what is causing this without knowing his alignment settings. The tires do not look feathered which would indicate a toe issue. I honestly believe this is an issue of excessive camber coupled with excessive wheel spin. When your wheels are tilted in a little too far and you "light them up" guess which part wears out first? It's fun... but does require a new set of rear tires at least twice as often as fronts.
