five7kid

No, not that type. I don't get my kicks doing big smokey burnouts...

Background: I got the car in Jan '14 with 124k miles on it. It had fairly new tires in decent shape at the time. Usage was mostly street driving (occasional track use, but no smokey burnouts). In the fall (after the end of the racing season) all of the tread still looked decent.

By spring '15 the rears were down to the wear bars with not much driving over the winter (~130k on the car by this time). I finally got a new set of Continental Extreme Traction in July to get the proper front/rear sizes and have a matched set (the tires that were on it were some off-brand that I had never heard of before, and the rears weren't the correct size - the tread on the fronts still looked pretty good, though).

Today, ~6k miles on the new tires. Fronts look great. Left rear so-so. Right rear is worn to the bottom of the tread on the outside only.

Given the age & miles on the car (to say nothing of its previous Arkansas 10-mile dirt road to residence life), some suspension wear is expected. I did already replace the bushings in the "dog bone" links with poly in fall '14 (bolts & links were metal-to-metal on a couple of ends). Also replaced the shocks with new Bilsteins on all 4 corners. The car exhibits rear end "throttle steer", which on here has been attributed to worn suspension bushings, so I picked up a full set of poly suspension bushings - but haven't gotten them installed yet.

It seems a little odd that the right rear is wearing on the outside if the issue is shot bushings, but I'm no C4 suspension expert.

So, question is, while I'm replacing the bushings (when I get to it), should I be looking for something else, or should new bushings and an alignment do the trick?

(Admittedly I haven't studied the shop manual yet to see if it has anything to say about this, or to understand the magnitude of the job I have on my hands.)

ovrebo1

Have you had the cars alignment checked?

five7kid

Not yet. Didn't figure it was worth it if I was going to be replacing bushings anyway. Drives fine except for the throttle steer.

ovrebo1

Tire wear is kind of a moot point if you don't know if the rear is within alignment specs. As for the bushing replacement, replacing anything on the suspension can potentially change your alignment. So if you already have the bushing and intend on replacing them, I would suggest throwing the bushings in and getting aligned.

five7kid

Well, that's what I was saying. No sense in checking the alignment before the bushings because it'll have to be aligned after the bushings.

It still doesn't follow to me that bushing wear would cause outer tire wear. I would expect the camber change to go the other way. But, again, I'm not familiar enough with C4 rear suspensions to know if that is the case.

1984Z51auto

I'd say do the bushings and then have a 4 wheel alignment by a good shop.

PatternDayTrader

Why don't you just take it to the alignment shop and let them tell you what all is worn out (if anything) ?

five7kid

Yes, that is the plan. The "good shop" part is the most iffy, though. There is a Corvette specialty shop in the area, it's a 45 minute one-way drive with no idea when they could get to it. To say nothing of the "Vette tax" being doubled (it's a Vette, and a Vette shop). They tend to specialize in C5 & up, too.

I don't want to double what I have in the car with just one job...

If I can finish up the 12-bolt install in the '82 Camaro, maybe I can tackle the bushing replacement this long holiday weekend.

five7kid

See "good shop" above.

We're talking a 20 year old car of a type which they haven't seen many of in the last 20 years. Kinda figured I could rely on the experience here better than a shop given their relative lack of experience.

2ooo-C5

Your getting not so great responses cause you have not checked the alignment.
The issue is 99.9% the alignment.

Fix the parts you want to fix and then align it.

If you want to know why the tire wear is what it is align it now. You will see its off.
Then align it again after you change the parts.

I did already replace the bushings in the "dog bone" links with poly in fall '14
Did you align it after doing that? if not you messed up the alignment then.

Anytime you buy new tires get the car aligned. Its cheap insurance for the tires.

PatternDayTrader

Suspension work is very straight forward. It takes no special talent or knowledge. Instead it takes experience with whatever alignment rack is being used. I would go to the highest volume alignment/auto shop in your area and just tell them what's going on with the tires and let them tell you what (if anything) is wrong. I would say something totally different if you were suffering from an electrical or drivability or even a heavy engine repair issue, but not suspension or brakes.

five7kid

Somehow I have presented myself as stupid. Funny, I never considered myself stupid. Unlearned at times, perhaps, but not stupid.

Yes, I know the alignment is off. Yes, I know at least some of the suspension components have exhibited wear. My other observed symptom, throttle steer, has been characterized on this august forum as being caused by other rear suspension bushings being worn - the tire wear I am now observing was not reported (as I recall) by those reporting the throttle steer symptom.

So far every recommendation offered here could be characterized as "just spend money and the problem will go away." Well, I've never considered that to be a very good troubleshooting method. And in my experience the repair shops' troubleshooting methods are designed to get me to spend more money, whether needed or not (a dealer recently quoted $450 to replace a $90 part on my wife's car that turned out to be nothing but a loose nut - it was in for the key fob recall repair). I am willing to spend money when necessary, but I do not like to troubleshoot by just replacing parts or spending money at a shop until the problem goes away.

So, again to specifics: The rear tire wear on the previous set of tires was even across BOTH tires, LONG AFTER I had replaced the dog bone link bushings. Yes, I know replacing the bushings "changed" the alignment - "restored" would be a better word, unless the car had previously been aligned with the worn out bushings (I have no direct proof of that one way or another, but given what else I know about the car, I find that highly unlikely). The car actually drove much nicer after the bushings were replaced, which is evidence that it had not been aligned with failed bushings. And, yes, it could be argued that I should have had it aligned at that time (but I had already read about throttle steer here).

And unless I'm really missing some kinematic reality, restoring the dog bone links should not affect the camber on one side only. But, I can be taught (which was why I started this thread in the first place).

And the front end is just fine. I know the car suffered some front end body damage early in its life, but front tire wear is next to nil, and when driving it doesn't do anything weird that can be attributed to coming from the front end.

I'll end by apologizing for wasting your time and valuable forum bandwidth. As soon as the Camaro is out of the garage I will pull the Vette into that stall and commence taking the rear suspension apart per the shop manual. And, yes, after I do all that I can do, I will take it in for an alignment by a competent shop (when I'm rich and famous I'll just buy my own alignment equipment and do it myself).

PatternDayTrader

No one said you presented yourself as stupid. No one implied your were stupid. No one said you have to spend money and the problem will go away. The collective opinion here seems to be check your wheel alignment. This is not bad advice. You don't have to spend money at whatever shop you go to. You could inspect everything yourself and then replace whatever is necessary and then have the alignment checked, unfortunately you skipped right to the forum asking about unusual tire wear .... and didn't like the answers.

1984Z51auto

I was not advising the OP to just spend money... with 120K miles on the subject Corvette there is a very good chance the rear bushings are all shot so, replacing them with new is about as sure a thing as can be. Doing it before alignment will ensure only one trip to the alignment rack is required to fix this issue. Didn't see anything about new dog bone/trailing arm bushings in the initial post.

five7kid

In the off chance that anyone is interested in the outcome, I'll provide an update.

I stopped driving the car until I could get out to the garage and get it in the air (I've been out of town a lot this summer). In the meantime, I saw a response in another thread by a member with whom I am familiar from another gearhead forum, who often provides sound tech advice here on CF, so I IM'd him for his take. He mentioned a few things that were never brought up here, and which I hadn't considered (which was the whole point of starting this thread) - tie rod ends, hub bearings, axle shaft u-joints, and the diff itself.

So, when I did get the car up in the air finally; well, I do have to eat a little crow here. Between not having been under the car much and this being my first Y-body rodeo, I hadn't noticed that the rear camber strut rods were not factory - they are in fact VBP units (the poly kind, not the ones with spherical rod ends https://www.vbandp.com/auto-parts/c4...96-detail.html ). The good news is all the bushings were in fine shape (the bad news is if or when these wear out, the stock replacement poly bushings in the kit won't fit ).

Everything else seemed fine as well, except the tie rod ends. I hadn't mentioned it here, but all of the front suspension parts with tapered shafts and castle nuts were loose when I got the car; all of which early on I had tightened to service manual torque specs and replaced cotter pins where necessary. Turns out that pattern followed with the rear suspension, as both tie rod end nuts were loose (although they did have cotter pins in the nuts). I tightened them to spec, and now the right side was snug - but the left tie rod end still had some pretty good slop in ball/socket. So I replaced the left outer and took it in for an alignment.

Only toe-in was off front and back, and front-to-back (and side-to-side). Caster/camber were still in spec. Everything was put back to spec, and I been driving the car again.

All I can say about the tire wear now is that the rears haven't gotten noticeably worse. But, I did let it go too long, so I'll be replacing those tires in the spring (it will see some road time during the winter, but not much, and never in wet or snow).

As for how it drives, again I didn't have any database on what to expect before, so that probably kept me from knowing something wasn't quite right sooner. It wasn't bad on the straights except for some following of ruts, but that has improved now. The biggest difference is when hitting a bump in a curve - it doesn't jump around now like it did before (not "about to lose control" jumping around, but "having to correct" jumping around). Much nicer.

Oh, I did also replace the spring bushings with the poly pieces in the kit. Next year I plan on tackling the front A-arm bushings (they don't look bad, but just to get the polys in), and will likely do front tie rod ends and hub bearings as well (the shop said there is the beginning of some movement in them, but not show-stopping yet). Then get it aligned again after the new tires.

So, that's the story. Tomorrow night and next Friday I'll have it at the track again for the last races of the season. After that it will probably get less road time until spring.

A Peter C4

You don't need new tires to do an alignment it's done by the wheels.Any alignment shop with fairly new machine should be able to do no problem,almost all newer cars need 4 wheel, just had my 94 C4 base done both front and rear where out $99 they said all bushings in good shape(I have sprayed them a couple times with sylicone)104000 Miles took 2 hours made me happy no work needed.My tires were wearing weird to.

five7kid

I didn't say you need new tires to do an alignment. I said the tires are excessively worn, especially the right rear on the outside. I'll have the car in again for an alignment after I do the front end work, at which time I also plan to do the rear tires - then an alignment.

And, you may have missed the instructions above: "Anytime you buy new tires get the car aligned." I certainly don't want to anger the CF gods again...