Tires: Solid-Axle Rear Tire Cupping, goodyear eagle f1, 2002 camaro ss

Question
I’m sorry this is so long, but I really hope you can help!  Okay, I'll start with a brief history just in case it may help.  I have a 2002 Camaro SS with 75,000 miles on it that I bought about a year ago, with 52,000 miles.  When I bought it, the guy had just put back on Goodyear Eagle F1's all around and these tires were GONE in less than 8,000 miles. As I was driving one night in the rain, I hydroplaned, spun like a top at about 40mph, and ended up slowing to about 10mph before sliding into a ditch.  I stopped in about 20 feet judging by the tire marks the next day, so I couldn’t have been going very fast by the time I left the road, and the ditch was not deep, and was only wet grass and mud, nothing hard at all…so I didn’t think it was enough to bend anything.  I was able to pull out of the ditch and drove home (carefully!).  Next day, I put it on the rack and checked for damage of any kind and found nothing, and the car drove the same.  A short time later, I had to replace the rear axle due to severe bearing failure, which was pre-existing before the hydroplaning incident.  I had the junkyard axle (which came out of an automatic so it had higher gears in it) inspected completely, and installed by an ASE-certified mechanic, along with a fresh set of tires.
So here's the problem:  Being a mechanic and car fanatic myself, I notice small details that many others wouldn't notice.  That being said, my rear tires are cupping in the center 3 treads, and these three tread lines are always colored differently than the outside tread bands, like they are touching the road more than the outer tread bands. The fronts are wearing severely on the outside and cupping slightly on the outside as well.  When I accelerate hard, I can feel a very slight notion of the car to want to turn to one side, not a pull in the steering wheel, just a very slight sort of rotation, yet when I let off the gas, it straightens back out immediately.  When I alternate quickly between accelerating and braking, it is more prevalent and easier to notice, as it wants to turn left during accel, yet dip and turn right during braking, all while the steering wheel stays straight and doesn’t try to turn.  It’s almost as if it rotates up and to the left during accel, but dips down and to the right during decel, without affecting the steering wheel, thought it is ever so slight and probably wouldn’t be noticed by someone who doesn’t know my vehicle as well as I do.  It does pull slightly to the right on the highway, but nothing major.  It feels almost like having a slack tire in the front.  Today, I replaced the outer tie-rod end on the front because it had play/pop in it, and I know that I need an alignment, but there is no adjustment on the solid rear-axle, and the gap around the tires in the wheel-well seem even, so does this mean that the frame is bent?  I can think of no other reason why the rear tires would cup.  I still have the old rear-axle just in case I need to compare anything on the two.  I have had these tires on for about 6 months now, and although the cupping on the rear tires is noticeable, it does not seem to be getting any worse, is not very audible, and other than that, they are wearing perfectly and have plenty of tread left on them.  If I take it to have it aligned, will they be able to tell me that something is out-of-spec? And if so, what would I be able to do if it is the solid rear axle alignment?  By chance, would the outer axle-shaft bearings have anything to do with it if they had play in them?  Thank you in advance for your help and any advice!

P.S. -The hydroplaning incident happened about 10 months ago and I have noticed no other effects.  Thanks,

-Alex

Answer
Alex,

It does sound like you need an alignment - and since you appear to be somewhat mechanical, I suggest you start by checking the squareness of the chassis.  There are quite a few books that have covered the subject - and I'll bet a few web sites, too - but I think "how to make your car handle" by Fred Puhn is one of th best.

And to correct a misconception.  Just because a vehicle manufacturer doesn't provide adjustability in his chassis, that doesn't mean it can not be adjusted.  Even solid rear drive axles can be moved forward and backward, which could change the toe.  Plus, these axles could be bent, so it might be necessary to unbend them.