My friend has a 95 E36 M3 that had the rear tires start pointing funny directions. I was fine then inexplicably had one rear tire seriously towed in and the other slightly toed out. It's at a BMW friendly alignment shop and the tech says he can slot some holes and get it to drive OK but can't get the alignment perfect.
We put it up in the air and couldn't see anything bent / broken also no missing bushings. I'm at a loss for what could've gone wrong. Any ideas?
Rear trailing arm bushing (rtab) failures would be my first guess. It's very common for these to wear out, and replacing them is an inexpensive DIY fix. First though I would fold down the trunk carpet and check the top of the strut towers for damage, just in case.
Barring damage caused by a wreck or incompetent towing the shop should be able to id a worn part. As ndwater suggested, the trailing arm bushings are a likely culprit followed by torn trailing arm mount pockets or the rear subframe tearing out of the body. Ask your friend if a curb encounter or tow company happened between fine handling and wonky rear tow issues. The rear lower control arms are super easy to bend, lazy tow guys will often use a chain or strap to pretzel said arm.
Don't let that guy start slotting E36 M3 or whatever he wants to do. Get new RTABs (either updated stock with limiters or powerflex), and a pair of adjustable rear control arms (The steel SPC/Eibach ones are cheap and work great, that's what my car has). Then never worry about any of this again.
Ya, it does sound like you should take it to a bmw specific shop.
I guess I don't understand why he needs to slot anything because both the rear toe and camber are adjustable from the factory.
Exactly: The lower control arms are spindly by All Knowing Teutonic Design. They're supposed to fold in a wheel impact and spare the subframe and unibody. Also, the rear trailing arm bushings are a chronic wear area.
Last winter I replaced every bushing and ball joint in my '36 M3, and the LCAs w/ the steel SPC arms. A word of warning on those - the inner end consists of an aluminum distance piece in a rubber bushing in the tubular steel end of the arm. One of mine crept so the steel arm was hard against the subframe so I made a set of limiters from molybdenum-filled UHMW polyethylene. I've been contacted by a half dozen other people on bimmerforums.com who want me to make sets of limiters for them, so it's a common issue.
http://forums.bimmerforums.com/forum/showthread.php?t=1231794&highlight=SPC+control+arms
As for alignment; my car is perfectly dialed for track days, very good for autocross and tolerable on the street with these numbers -
(AST 4100 single adjustables/Vorshlag camber plates/ 550#F 625#R/H&R F swaybar 28mm adj ends full hard/UUC swaybarbarian R full soft - Z1s or RA1s)
F: -3.2 deg. negative camber - max caster - zero toe. R - 2.1 deg. negative camber - .125" toe in PER SIDE .
That's a lot of R. toe in but it makes for great drives out of upset autocross corners. Tire wear is probably not great, but most of the annual miles are to and from and at events.
I'll keep an eye on the inners on my spc arms then. I haven't noticed that, but I've had them on less than a year.
My alignment is very similar to yours (a little less camber all around, same toe, but mine is a year round daily driver). I'd say you're right on for a dual purpose car.
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