pewter82

Sorry for no digital pic, but bear with me on this. Simply put i had a 4 wheel alignment done on my 91 GT after adding two new rear tires. Now the car feels loose at high speeds and tonight I notice after looking straight at the back end (from bumperlevel about 10 feet back) that I can see tread on the left rear tire Above the line where the rubber bumper meets the metal. And on the right side the tread is not visable that high up on the tire. Its almost like the left tire is pointing in ,and the left is straight up and down.

This can't be normal and most likely might be the loose feeling at high speeds?

Jason

91GT India Red/Tan GTS Rear RMB 56k
82 S Pewter/Navy auto 57k

Garth S

While I do not follow your description too well, your conclusion would suggest excessive toe-in on the left, and possibly insufficient camber on the right.
Normally, with an alignment, you get a print-out of 'before and after' specs. If the final result is actually way off, it's likely the print out shows it as good - meaning that the print-out would have shown the 'before' readings as off spec in the reverse direction ( eg., if the 'toe' was in reality, on spec, and the Tech's set-up told him that it was -ve as a 'before' reading, then he would have cranked it +ve until the 'after' reading was correct - leading to excessive toe-in!) This all presumes either a faulty set-up, of a rack out of calibration - were it incompetence or stupidity , no logic applies.
So, firstly, check your sheet for any large swings to meet spec alignment: if you do not have the sheet, the shop may have it on file/memory.
Not knowing how many miles on the new tires, I'll suggest you do this anyway: Assuming pressures are fine, lightly run your fingers across the tread face in both directions. What you are feeling for are sharp or feathered edges - and/or a difference between the two tires.
Perhaps that's something to start with. With no facts, it is premature to suggest that corrective action is req'd. The archives have some great stuff on alignments and checks.

pewter82

Thanks Garth, The tires have about 50miles on them and I did not recieve a print out. Your idea seems correct on paper, but the tech has NEVER done a 928 and most likely used to working on Ford's, because I work at a ford dealership that also has BMW and Porsche techs. The look of the wheels and tires just looks wrong.

heinrich

I would like to mention that I've seen many many 928's in excellent shape, with different fender clearance between left-rear and right-rear.

Garth S

If the Tech had never done a 928, it is possible he broke the cardinal taboo: NEVER lift the front end after placing the car on the rack - or if it is lifted, the front must be recompressed as per the FSM Method. Were this the case (of uncompensated lifting), it's a sure thing that the front is misaligned!! There are lots of posts on this, and the benifits of using the Hunter 400 machine, etc. Hopefully, this was not the case - but be sure!!.
As Heinrich mentioned, some 928's have differing rear fender clearance: there was a very recent post on this, because I remember adding 1.5 cents of comment - do an author search if curious. Good luck!