fnsblum

Would you please explain this statement? Later! Frank

ljmattox

As well as, given the $$ spend to buy tires for these cars, you may want to form or obtain a second opinion.

*Are* the fronts cupped? If they're bad enough to "prevent them from being balanced" that may even be visible, if not, some personal finger-tip evaluation could help you understand what's up.

The rears are cupped also, that badly? Or the tech was just recommending replacing in sets of 4? At 17k miles, maybe it's just as well.

Still though, I'd do a little personal examining of my own, or get another shop to have a look. Just personal history...

Non-Corvette experiences: (1) 6+ hours at NTB with my MBZ 190E while they balanced/re-balanced 4 tires multiple times, "flipped" them on the rims, etc. with test drives in-between. No joy, still shaky. Shop manager said, of 90% new tires, "yeah, they're shot, we've tried everything. Must've run 'em too long unbalanced. You need a new set." Shop #2: balanced, smooth as glass, first time.

(2) WS6 Trans-Am in the shop for not-cold A/C. "Your compressor is shot (at 71k miles). $1400". Hmmm, I'll think about it. Shop #2: leak test proved sound, refresh some refrigerant...3+ years later, still cold and working fine.

etaylor14

I have a lifetime alignment from Firestone. It cost me $179.00 and is good at any store in the country. IMO it is a great deal!!! I can get it checked every week if I want to.

R&L's C6

I was planning on replacing just my front tires next spring , is there a reason I shouldn't do this ?

Gearhead Jim

Different tread depth between front & rear tires may cause handling differences.

If the front tires have more tread, they might actually have a bit less grip on dry pavement and produce some understeer in hard cornering. Normally, not a significant hazard.

And if the front tires have more tread, they almost surely will have more grip on wet pavement, so you can get rather sudden oversteer in the rain. Not a good thing.

There is no hard and fast rule that I'm aware of about different tread depth. I like to keep tread differences to 2/32" or less, but that's just me. And if you are continually wearing out your fronts first, then you'll only have equal tread for a couple of thousand miles at the "crossover" point.

If you think about the issue when you make your choices, and drive carefully in rain, you'll probably be ok.

Kenny94945

Cupping vs feathering.
Can your trust the knowledge of this tire tech?
Can you confirm the diagnosis.

FWIW I always thought cupping mostly came from a bad shock.
If both tires are cupped I would not think it is a shock.
Yes, alignments change over time and could be incorrect from the get go.
Bent suspension, worn rubber bushings, loose suspension bolt can also be an issue to look for.....Sway bar link issues seem to be a popular issue on this forum.

So...with runflats I do not think there is much choice if you rule out Goodyear, Firestone and French Michelin.

OK then...Ask around for a quality shop in your area. Check all the bushings for damage/wear, re-torque on all front end bolts, install your new tires, road force them correctly then check ride height and corner weigh and lastly re-align to the spec you like (wear vs. handling)

You did not mention if the vibration occurs while braking? Might check for warped rotors.

Once aligned you can test with a tire pyrometer to check your setup.

In other words start from scratch.

This work/ reward can be fun if you can do some of it yourself.

AORoads

"...If you think about the issue when you make your choices, and drive carefully in rain, you'll probably be ok.

While I might agree with Jim above, my only question to R&L is: How do you "drive carefully in the rain" when an emergency situation presents itself at say, 65 mph? If you think about it, emergencies and accidents don't announce themselves in advance before you walk out the door, or in a 2-minute warning. Just be careful out there.....

R&L's C6

Thanks for the reply. Even though I only have 15k on my car the inside fronts are wearing much more the the outsides. The rears look almost like new. I had it aligned last year but the inside fronts still are wearing faster. I don't know if it's to much spirited driving( I don't track the car) or a bad alignment job.

Turbo6TA

Tires wearing on the inside ... As I said before ... Too much camber.

Set the camber to about -0.4 degrees and that won't happen.

Anything much more and you eat up the inner side of the tires.

fnsblum

Deleted

okbkvette

ok, so how do you tell if you've got a damaged suspension part? I thought bad alignment (excessive toe in) could cause cupping as well? I just finished a couple of long road trips, 2500 each time, noticed on way back on the last tripo more road noise creeping in, I'd been down that road before in my c5. I ran my hand over tire, and had cupping (at least what I have always thought was cupping) on inside of both fronts. Checked the tread with my gauge. Drivers, still 6/32 across the tread, slight inside cupping. Passenger, much worse, 3/32 to 5/32 outside in.
Went to my normal align place, sure enough, toe much toe in on both, passener side, WAY out. 500% of normal. So, does appear to me that being out of alignment can cause cupping.

So, going to have to get some tires, but if I've got some bent suspension pieces, how do you get that checked? I haven't hit anything I can recall, and car has never been towed or trailered, other than when nee from factory to dealer. I felt the alignment was my problem, since clearly was way out of specs, and to much toe in I thought caused cupping.

So, where am I?
thanks all

Gearhead Jim

FWIW, we put Goodrich KD (not KDW) runflats on our C5 Z51 w/ Bilstein shocks. They were both directional and asymetric, so each tire was specific to that corner of the car and could not be moved around.

They were the stickiest street tires I had ever driven. They were also the most noisy and harsh-riding tires i had ever driven, with a rather sudden breakaway at the limit. Had alignment done about the same time.

Anyway, the fronts developed such bad cupping that I replaced them after about 18k miles; the vibration in the steering wheel was too annoying and the Hunter Road Force Balance couldn't get rid of it. Did another street/track alignment and the second set cupped just as badly.

We never could find anything wrong with the suspension or alignment, and the Firestone runflats I finally put on the car, were nice and even with about 1/4 tread remaining when we traded the car.

Some tires just seem to cup very easily.

personsjn@gmail.com

I've owned 6 Corvettes, 1996, 1998, 2000, 2004, 2007 and now a GS conv. 2010. The GS 2010 had worn out front tires at 10,000 miles and the rear were only 1/2 worn. None of the other cars had this problem. Is this common for the GS and other late models?

mikeCsix

Bent suspension parts show up in the alignment procedure. I had a problem with my left front, could not get the alignment to come in. Ended up replacing the upper control arm and knuckle to correct it. The main issue with the alignment was not being able to set camber less than -1.7 degrees. As long as both sides are the same and toe was set properly, the car handled okay - even on the track. I looked at the parts and could not tell if they were bent, car had less than 10k, tires were not overly warn out (GY RF supercars - this is the Z-51 standard suspension for a 2008).

After replacing the components and the rear camber adjuster cut loose on a hard turn at the track, I replaced the adjusters with the pfadt system. Pretty irritating when something like that happens at a track day after spending all the time and money necessary for setting up the car for track days, and I'm on the light end as far as preparation goes - upgraded the brake lines, flushed the brake system and installed Motul 600 brake fluid, then later in the year, tire upgrade to Michelins. Spent more on wheel alignments this year than I ever have.

A big FYI, for the first 7,000 miles, wheel alignments are considered warranty work. I had the local dealer check mine twice - they said it was out of alignment both times and claimed to have brought it back in spec but noted difficulties with the left front. Took it to an Acura dealer to replace the brake fluid and had them check the alignment and found it out of spec and not able to bring it into spec. and it was out of the 7k mile range. $700 later I had new suspension components installed at the Acura dealer plus the pfadt camber adjusters installed. The Acura dealer alignment wasn't all that great (no experience with pfadt), took it to a race shop/ custom car shop, had the michelins installed and the alignment checked (rear okay, front was all over the place), I worked with the tech this time (actually at the machine as I was getting tired of being told all was okay only to find out differently from someone else) and was able to bring the alignment to exact specs. The car handled much better at the track and was my best/fastest day all year.

vdavenp802

Update on tires after alignment at Chevy dealer.
Seems a bit better, but really hard to say. Have driven about 500 miles so far. Still have the vibration >80-85. It may in fact still be there at lower speeds, I just don't feel it in the steering wheel.
Dealer did not find any worn or bad suspension components.
The tires seem to howl more that before.
The cupping may be more of a feathering effect, and again, it appears to be some better as I inspect the tires myself.
Will not get many more miles until next spring, when I'll try again, but frankly can't tolerate the noise much longer, especally on longer trips.

If it weren't for the French thing, I'd have a set of Michelins now. I may take a look a the GY gen 2 F1's.

Thanks for all the suggestions.

Gearhead Jim

Most of the Michelins are made in the U.S.

AORoads and I discussed a lot about our loyalty to Goodyear before buying Michelins, but the Michelins are clearly a superior tire.

The PS2 runflats (regular Coupe size) that I bought this Spring had the rears made in U.S., fronts made in France. Lots of jokes about that...

We used up 3 sets of Supercars on our Z51s, then went to Michelins. After a summer of driving on the Michelins, I'd buy them in a heartbeat regardless of where they were made. Slightly softer, much quieter, and much more predictable at the limit.

08VRZ06

Yes... The Z06 and the Grand Sport tires are wider and have a softer rubber compond that the base model Corvettes. Was the tread worn evenly across?
Also the alignment specs from GM are so broad that even if you were to take it in and have it checked under warrenty they would probably tell you that it was within spec. Need to take it to a good alignment shop and have the toe set to 0.0 for front and rear, 8 degrees of caster on the fronts and -0.4 camber on the fronts and -0.5 camber on the rears or you will quickly wear out the tires...

Mark

hihoSilver

Mine was out of alingment and pulling to the right when I bought it. The dealer aligned it. It was way off. I dont have the alignment sheet in front of me.
So, is the factory specs for a GS going to be setup as a track car? I thought I read this somewhere. I dont track my car, just cruise. If anyone can post the factory specs along with the street specs (if they are different) I would appreciate it.