Abnormal tire wear/alignment
 

On a recent trip across SD, had felt a slight vibration/shimmy (75+). Had the tires checked by Goodyear and they are at 40% left. 18K, on standard vert 07.

Took it to have a road force balance and the tech sad tires(front) were too baldy cupped to balance on the hunter equipment. Need new tires all around.

WTF?

Can this be?

Shocks, bearings and all other suspension parts were checked while wheels were off car and they reported no visible issues.

How common is this. I mean 18k miles and a whacko alignment. I've been driving for a good many years(shortly after rubber tires were invented lol) and this is a first. I am generally a moderate driver given to an occassional spirited episode (carefully).

No off road stuff, or gravel roads and the like. Mainly town/interstate.

Spouse does drive the car too.....

Don't want to have more goodyear, but don't want to replace 4 tires, rears have 60% left.

Suggestions, thoughts, ideas welcomed.

Also key, must stick with runflats. Won't buy anything french anymore, I've owned my last firestone ( on an 99 exploder, thank youvery much).

I think that leaves Pirelli.

:cheers:

On the OEM tires, the rears start with more tread than the fronts. Fronts have 10/32" of tread when new, rears have 11/32" of tread. I got about 32K out of the front tires on my previous 06 C6 w/o Z51.

Your 40% left with 18K on the front tires says 30K total. Other problem with the tires is something else and I don't know tires, so I can't help you with what caused the cupping.

The cupping can be caused by the tires being out of balance for a period of time.

I tried a set of Pirelli's on my Mercedes Sedan one time and they were horrible for wear and noise and had a tendency to wander on the freeway. Discount tire took them back and I went back to the original equipment Michelin's, 10 times nicer to drive on and wear far far better. The Pirellis would flat spot over night and made a thump every time they rotated when they were cold. It would take a few miles to get back to normal every day.

On my vettes I have replaced the Good Years with Michelin AS ZP's and they go around 45k miles and are far quieter and the wet traction is superb.

Before replacing your tires have them run the wheel alone on the balancer with no tire and make sure it's not bent. Some bends are less visible than others.

Cupping is from out of balance or can be worn shocks on an old (not your) vehicle.

Whatever tire you go with get it Roadforce balanced from the start. A Roadforce balance will reject all tires that are out of round. Out of round tires can never be fully balanced.

obviously, your car needs more timely attention. that's not a criticism of you, just a statement of fact. there is no such thing as a lifetime or 5 year balance job, nor of a similar time frame for an alignment. let that be your guide since you could drive out after having both done, hit some railroad tracks just the wrong way, and have to do it all over again. delicate? maybe, maybe not. I do know I was told that for some reason C6s don't hold an alignment all that well. as to the balance and cupping, hard to believe you lost weights on two different wheels up front, but it's possible.

I'd suggest at least a once a year re-do of both, no matter how much or little you drive your car. otherwise, it's 300 for each front tire, give or take since there's not that many runflats made in that size that aren't french or from exploders' fame. :rock:

I just wore out my GY R/F's at about 11k miles. Track sessions will do that, I've done three this year so its understandable. During my first track session, I lost the camber adjustment for the right rear, it went dramatically to '0' or reset itself midway into a fast left sweeper. My reason for bringing this up is AORoads has a point about these cars losing their alignment. I changed over to Phadt racing's solution and after 2 more sessions, the alignment seems to hold. I'm replacing the GY's (Supercar, I have the Z-51 option on my '08) with Michelin Pilot Sport PS2 ZP's to finish the last hpde event this year. Next year I will go to R-compound tires mounted on different wheels for track days, preserving the Mich's for street. They are supposed to be quieter tires (which is what I'm after) than the GY's, so will see. I'll have the alignment re-checked with the new tires but after looking at the Pfadt solution, I'm reasonably confident the alignment will not have changed. It looks to me like the only way it could change is to bend some parts.

Periodic checks are good to do. I didn't on our new GS vert, and it ruined the front tires in 5K+ miles! The best rule of thumb for Corvette owners is "get an alignment"!! What is the Pfadt solution?

What's the average price you folks are paying for an alignment?

These tires won't get alot of mileage with lots of camber. Unless your road racing the car, I am of the opinion that you don't need anymore than -0.4 degrees of Camber on either the front or the rear wheels.

Some folks are using as much as -1.4 degrees of Camber, but while it really helps in hard cornering, it also chews up the tires on a daily driver.

As for Toe In: From everything I have read, the number is easy to remember: 0.0 degrees of Toe In for both the front and the rear wheels for best tire life.

.

My Chevy dealer charged me $89.95 for 4-wheel alignment.

PDF file I saved that was put out by PFADT Race Engineering says for 100% street, they recommend -0.8 deg camber, 8.0 deg caster, and 0.0 in. toe for front and -0.5 deg camber, 0.0 in. toe for rear.

the independent Corvette shop I go to charges $90.

To the OP-
Your alignment could have been whacko right out of the factory.

The factory alignment specs are pretty broad, but all three of our new Corvettes (2001,2006,2009) still had at least one setting that was out of spec.

IIRC, they tightened up the factory alignment procedure for 2011. 'Bout time.

Jim,

Do you know what the factory alignment specs are the the 2011 Corvettes?

Good post. Later! Frank

PS: Alignments go out not so much from running over things but from running into something. Bounce it off the curb one time and you better have it checked. Ask me how I know this if you are interested.

Sorry, I don't know. I can tell you what they said for our 2009 when the Service Manual was published, but that doesn't include the GS and even the other numbers may have changed.

Part of the problem is that the original specs were overly-broad (they may or may not have been tightened up), and the other part was that cars were coming out of the factory with alignments that didn't even meet those loose standards.

I agree with your comments about camber and toe, for us non-racers.

Now here is the problem! Just blame it on her... :lolg:

Are you talking about cupping or feathering? C6s will feather their tires if you don't align your car often. Cupping is a serious issue. I agree you should look at the rims as it doesn't take much to bend them.

Personally I'll rebalance my tires and do an alignment every year on my C6. With tires that cost $500-600 a piece it is real cheap insurance. If 18k bothers you don't even consider getting a GS where 15k is about the max and it will cost $2k to replace them.

You are right about the broad specs Jim. It has been this way for at least the fifty years I can testify to. The broad spec has always had a listed desired, preferred, sweet spot of what ever the industry chose to call it's setting. As an example I think my 08 base coupe camber spec is approximately - .4 + or - .5. Now with very few exceptions the factory desired setting of -.4 will give very good wear. I put new tires on my car last June. The camber was at -.43 on both fronts. Toe was 0 all around and the cross caster was within .4 so I and the Tech decided to run it and watch it for awhile . They now have near 12K and they are wearing perfectly even all the way across. The good shops with a good Tech should have no problem getting the alignment spot on. I would think the factory would do a little better on the Vette than they do on the other GM makes. Later! Frank :cheers:

You don't want more tread in the front wheels of your car than in the rears; so this suggests you should replace all four tires. Now if your politics tells you not to buy French products, you obviously don't want Michelins, but otherwise they are a great product, and always have been. I used to think the French were only good at wine making and drinking same, but I came to respect their engineering capabilities after working closely with them and observing their remarkable accomplishments.

Cupping
Cups or scalloped dips appearing around the edge of the tread on one side or the other, almost always indicate worn (sometimes bent) suspension parts. Adjustment of wheel alignment alone will seldom cure the problem. Any worn component that connects the wheel to the car (ball joint, wheel bearing, shock absorber, springs, bushings, etc.) can cause this condition. Worn components should be replaced with new ones. The worn tire should be balanced and possibly moved to a different location on the car. Occasionally, wheels that are out of balance will wear like this, but wheel imbalance usually shows up as bald spots between the outside edges and center of the tread.

Cupped tread wear comes from the tires "bouncing" at certain speeds due to the unbalanced weight of the tire. A rough parallel might be to consider how a washing machine in the spin cycle can begin to "bang off balance" when the weight of the clothes is unevenly distributed. To balance the tires, weights are placed on the rim to keep the tires rotating smoothly at any speed.

Just some stuff.............

if you take your hand, and run it lightly across the tire surface, .....let your fingers do the walking, you can feel if you have cupping or not.... front to back....