Wearing on the inside....

I went to get my alignment done. I had 3 shops look at it two of which is a pontiac dealership. The last dealership said, I have negative camber in the rear and there is no way to adjust it. I need two lower control arms. Is that right or did our cars come from the factory dialed in with negative camber in the rear. See, I let my buddy drive my car....I know, I know....but, he spun out and hit a curb on the driver side. He cracked the edge of the rim and bent the adjustable tow link-driver side. The tech from the last shop told me the driver's side is in spec and the passenger side is out of spec....Can someone shed some light on the situation?

i was always getting wear on the inside of my tires when i took it to my friend and he said that they put a spacer on one side and not the other side of the car from factory, so he just balanced them a little negative on one side.. he said there was really nothing he could do unless he took the whole axle apart, but i have heard a few stories like this.. this was on my front end though

i have a 2004 GTO and i had to buy new tires for the back cuz when i launch my car the ass goes down and my tires butterfly in-ward so i just be using the inside of my tire. now i have 275/40/17 and they seem to have fixed the problem, but i also just run them @ like 25-27 psi.

And by running 275 on back, dont you get any fender contact with the tire. Or did you roll the fenders. I was thinking of also running 275 out back with a 17 inch wheel.

Your rear cradel is probably out of alignment. You should beable to go to a "highend" alignment shop or a "highend" bodyshop that has a computer frame rack and get that done.
Yes it will make a difference. You will see a minor increase in inside wear just because of the IRS.
I usaually will have the dragradials taking off the rims and flopped around about half way through the tread use to equal out this wear pattern.
I would highly recommend that you repalce the soft stock rubber bushings with BMRs or someone elses Poly bushings before you spend the money on getting the cradel realigned.

By the sounds of the curb incident, you'll probably need to get another lower control arm. I saw one recently in the parts for sale section on ls1gto.com for $100 (I have one lying around but it's the LH side). So you if you have to change out the lower control arm, you might as well change your control arm bushings. Since you need rear camber adjustment you'll probably want to go with a camber adjustment bushing like this:

http://www.midwestpd.com/catalog/pro...roducts_id=315

or this:

http://westfield-et.com/product_info...products_id=61

That way you can adjust the camber on the rear. For the inner control arm bushing you'll want to run a solid polyurethane bushing.

Another thing that helps with the negative camber is changing your rear springs. I'm running some stock height 'king springs'. They're the same height as the stock springs, but a higher spring rate. Therefore not as much rear end squat.

Like the others mentioned your rear cradle is probably out of alignment. Rear cradle aligment requires a special tool that all GM dealers who sold GTO's have, but usually don't know what it is. From what I understand at most dealers the tool is still new in the box in the tool room. Another option for a rear cradle aligment is a pedders dealer like what I linked to above. I hope this helps.