Need Wheel Balance Help

[Michael M.]

My 09 has a slight vibration in the seat while driving 40 to 70 mph.
Dealer load balanced the wheels with a Hunter Load Banance Machine.
They replaced two tires. picked up the vehicle and no change, still has vibration in seat. They checked it again the next day and rebalanced the wheels and said there is no problem that all the wheels and tires are within spec. I asked how much weight was on each wheel. L/R 8-OZ, L/F 1-OZ, R/R 6-OZ AND R/F 3-OZ. They said there is nothing more they can do, its within spec.
While getting an oil change today at a friends shop, I explined the problem. While he had the vehicle on lift he rotated the wheels with a dial indicator set to the rim and found the rim to be out of true at the valve stem about a 1/16" at the same location for about 8-10" on each wheel and odley enough the wheel weights are 180 out from the area that is out of true.
Does any one know GMs spec for new vehiciles and amount of wheel weight allowed?
Any suggestions would be appreciated!
Second does anyone have a number for the South Central Pa GM rep?. I'm getting no where with my dealer.
Having a $57k vehicle I don't like driving is not a good sitiuation.

[Edward J.]

Re: Need Wheel Balance Help

Mike, the rear weight is a bit excessive, 2-3 oz. should be about the norm. being theres so much weight, I would have them try breaking down rear tires and rotating a 1/4 turn until they get the least weight possiable.

some of the high tech wheel balancers can also balance the wheel before the tire is mounted on the rim.and then balance the tire and wheel together.

When you get a vibration in the seat of your pants, this generally means rear tires and by the excessive weight in the rear it makes since that theres something out of balance in the rear. has anything been done to suspect something other than a tire, such as rear suspension been apart maybe a bad pothole in the road ?

[Jack H.]

Re: Need Wheel Balance Help

I agree here! Many shops 'blindly' add weights to get the modern spin machines to say 'OK'. Often, simply re-orienting a specific tire on a given rim will wind up with balance being achieved with MUCH less weight.

On the issue of wheels being 'true', that's one that's often missed and even if a out-of-true wheel is balanced, it doesn't solve the issue of it spinning with correct concentricity. Continuing to drive on such typically winds up with the tire taking a 'set' (uneven wear) and the vibration annoyance to NEVER go away.

When I fought this issue on my '71 (factory original dated wheels that'd been 'curbed' in their prior life and were out of round as a result), the wheel shop mounted them on a stub axle and used dial micrometers to check for concentricity in both the radial and axial directions. They found out of round conditions on three of the five wheels and set about the process of truing them.

That's essentially the 'art' of a stragegic WACK here another WACK there followed by remount, rotate and measure again. I asked the truing tech what his goal was and he said most felt concentricity should be within 20 mils, but personally, we wanted to see 10 mils or less. A 1/16" reading amounts to 62.5 mils.

When they finished the task of truing my wheels, I remounted the original tires, balanced the wheels and drove off. I was shocked to discover I still had objectionable vibration (speed specific at/near 60 mph).

I went back to the wheel shop and talked to the owner, heck my tires less than 5K miles on them. He said that was enough for the rubber to have taken a 'set' due to the out of round condition of the wheels and that I should discard them and buy fresh rubber.

I had to get a second opinion on that and found a knowledgeable tire distributor who AGREED with the wheel shop. He dismounted and spun up each wheel letting me watch so I could see both 'squirmer' and 'hopper' tread profiles in action.

I put on fresh rubber and the car drove like a DREAM! It's been that way for +50K miles now... What I learned: raw balance isn't the whole story!

[Edward J.]

Re: Need Wheel Balance Help

Jack, as you stated its all about the time and pride you take in the work you do. As for the newer run flat tires it takes about twice the time of a normal everyday car tire to break down and mount. balancing a problem tire will take some time, If the tire shop you deal with is willing to sell you the tires I would think he would want a happy cust.

Mike keep in mind that there is alot of new technolgy with wheel balancers, now more than ever with the newer run flat tires, if the right equipment isn't used you just get as you have, a so-so job.

[John D.]

Re: Need Wheel Balance Help

Michael,

Who is the dealer I may be able to help.........


john

[Terry M.]

Re: Need Wheel Balance Help

My 09 has a slight vibration in the seat while driving 40 to 70 mph.
Dealer load balanced the wheels with a Hunter Load Banance Machine.
They replaced two tires. picked up the vehicle and no change, still has vibration in seat. They checked it again the next day and rebalanced the wheels and said there is no problem that all the wheels and tires are within spec. I asked how much weight was on each wheel. L/R 8-OZ, L/F 1-OZ, R/R 6-OZ AND R/F 3-OZ. They said there is nothing more they can do, its within spec.
While getting an oil change today at a friends shop, I explined the problem. While he had the vehicle on lift he rotated the wheels with a dial indicator set to the rim and found the rim to be out of true at the valve stem about a 1/16" at the same location for about 8-10" on each wheel and odley enough the wheel weights are 180 out from the area that is out of true.
Does any one know GMs spec for new vehiciles and amount of wheel weight allowed?
Any suggestions would be appreciated!
Second does anyone have a number for the South Central Pa GM rep?. I'm getting no where with my dealer.
Having a $57k vehicle I don't like driving is not a good sitiuation.

I hope the machine they are using is a Hunter Road Force balancer. The latest is the GSP 9700. These are very sophisticated machines and require a good deal of skill and training to get the most from them.

http://www.hunter.com/pub/product/balancer/4159T/index.htm

These machines will direct the operator to rotate the tire in relation to the wheel to achieve minimum out of round and optimum weight efficiency. That said if the wheel is out of round balance will not help eliminate the vibration. The latest wheels are very "mass efficient" but they are also quite fragile. A good pot hole can execute a C6 wheel.

BTW: 8 oz sounds like a lot for one wheel.

Good luck with the GM rep.

[Joe L.]

Re: Need Wheel Balance Help

My 09 has a slight vibration in the seat while driving 40 to 70 mph.
Dealer load balanced the wheels with a Hunter Load Banance Machine.
They replaced two tires. picked up the vehicle and no change, still has vibration in seat. They checked it again the next day and rebalanced the wheels and said there is no problem that all the wheels and tires are within spec. I asked how much weight was on each wheel. L/R 8-OZ, L/F 1-OZ, R/R 6-OZ AND R/F 3-OZ. They said there is nothing more they can do, its within spec.
While getting an oil change today at a friends shop, I explined the problem. While he had the vehicle on lift he rotated the wheels with a dial indicator set to the rim and found the rim to be out of true at the valve stem about a 1/16" at the same location for about 8-10" on each wheel and odley enough the wheel weights are 180 out from the area that is out of true.
Does any one know GMs spec for new vehiciles and amount of wheel weight allowed?
Any suggestions would be appreciated!
Second does anyone have a number for the South Central Pa GM rep?. I'm getting no where with my dealer.
Having a $57k vehicle I don't like driving is not a good sitiuation.

Michael------

I'd say the wheel/tire assemblies having the 8 oz and 6 oz of weight required is a "red flag" that there's some other problem. Curiously, though, these are both mounted on the rear which should somewhat reduce the effect on vibration.

In the old days, some wheels and tires were marked to facilitate balancing. Wheels were marked at the heavy spot and tires were marked at the light spot (or, vice-versa; I've forgotten). In any event, when the heavy spot and light spot are aligned, this minimizes the need for balancing weights.

In today's world I don't know of any wheels, stock or aftermarket, that are marked as to the heavy or light spots. Perhaps modern manufacturing methods have made this unnecessary or, perhaps, they just don't do it anymore.

The only tire manufacturer I know of that currently marks the tires for light (or, heavy) spot is Yokohama. That doesn't help me any because I don't use Yokohama tires. Maybe I should, though.

[Terry M.]

Re: Need Wheel Balance Help

A story I told here once before: My second set of tires on the 2008 Z06 developed a small vibration from the rear of the car. It was cyclical, and most annoying at 65 to 75 mph. I requested the tires be rebalanced, but was told they were fine. I learned to live with the vibration -- as I said it was minor.

When I bought new rear tires the tech showed me one of the old rears had a crack on the inside. It couldn't be seen until the tire was off the wheel. I am convinced that was the source of the vibration. My best guess is it was damaged by a pot hole.

[Duke W.]

Re: Need Wheel Balance Help

Modern tires/wheels are matchmarked. There is a yellow spotch of paint on the tire that should be lined up with a mark - usually a small white dot on the wheel. It's usually easiest to locate the tire mark and then look for the wheel mark in the adjacent area of the wheel (It may be very faint.) to see if the wheel and tire were properly indexed. Indexing these marks next to each other lines up the low spot of the wheel with the high spot of the tire to yield the roundest assembly of wheel/tire. A slight out of round condition can yield a vibration that no amount of balancing can cure.

Tires are also often marked with a red dot to indicate the light spot. If the above matchmarks cannot be found, the next option is to index the red dot with the wheel valve stem hole.

Modern Corvette service information should include data on wheel lateral and radial runnout. If I understand correctly, you are saying the wheel has 1/16" lateral runnout, which is probaby excessive. Excess lateral runnout can cause a vibration.

The only runnout data I have is for seventies H-bodies - .045" lateral and .025" radial. So 1/16" lateral is probably out of spec.

The Hunter GSP 9700 mentioned earlier can measure runnout in addition to balancing the assembly, so in cases where vibration is still an issue after balancing the 9700 should be used to measure runnout to determine if the wheel or tire is defective.

It sounds like you are in process of contacting the zone service rep, which is the right thing to do, and the cure may be new wheels that are within runout spec.

Duke

[Michael M.]

Re: Need Wheel Balance Help

Thanks to all for your input.

Had an appointmrnt with dealer on Wed. after a lengthy conversation and a long test drive with a senior tech (35 yrs exp.), they finally agreed there was a vibration.
After two days of them checking the vehicle, they called and told me today they were ordering 4 new wheels.

[John D.]

Re: Need Wheel Balance Help

michael,

My $0.02 is that the dealer may not yet be on the right path here. The chances that four wheels on one car were all defective at the same time sound slim to me unless they were damaged in some way.

Key Questions to ask your dealer:

Have they call GM technical assistance for guidance ?

Have they driven your car with an EVA (electronic vibration analysis) tool. if so what were the results.

[Dick W.]

Re: Need Wheel Balance Help

Michael, I would pay attention to what John Daly posts. He is in a position to know what is going on and can possibly be a very good asset to you.

[Joe L.]

Re: Need Wheel Balance Help

michael,

My $0.02 is that the dealer may not yet be on the right path here. The chances that four wheels on one car were all defective at the same time sound slim to me unless they were damaged in some way.

Key Questions to ask your dealer:

Have they call GM technical assistance for guidance ?

Have they driven your car with an EVA (electronic vibration analysis) tool. if so what were the results.

John-----


I TOTALLY agree. I cannot see all four wheels being bad. Of course, the dealer may be going with the "shotgun" approach. In other words, if he replaces all four wheels he's bound to get the one that's bad. Then, 3 perfectly good wheels get scrapped.

However, the above "shotgun" approach only works if the problem is actually the wheels. If it's something else they'll be "back to square one".

My recollection here is that there is a pretty extensive chapter on diagnosing and correcting such problems in the GM Corvette Service Manuals and this goes back a long way (I think my 1992 manual has one). It doesn't sound like this is being used to get at the root of the problem here. That would not surprise me, at all. My experience over the years has been that dealer service departments rarely use the service manuals or the electronic version of same.

[Clem Z.]

Re: Need Wheel Balance Help

have seen this problem caused by a out of balance disk brake rotor.

[John D.]

Re: Need Wheel Balance Help

Joe,
I couldn't agree more. Technicians on the flat rate pay system are at times reluctant to put in extensive diagnostic time on difficult problems when it may be easier just to do something (change four wheels) and move on to the next job. Also getting paid extensive diagnostic time can be a hassle, particularly if the tech was "barking up the wrong tree" so to speak.

The best shops have an experienced shop foreman who is not on flat rate who can spend the time it takes to work on difficult problems. In this case he would drive the car with the EVA tool attached to the seat frame to determine the nature of the vibration and the best way to solve it.

There is also a very good chance GM will ask for these four wheels to be sent back for analysis. If they are not found to be defective the dealer will have some explaining to do.

(FWIW Flat rate means the technician gets paid by the dealer and ultimately the manufacturer the published labor time for the job performed.
For example if the published time to change a hub bearing is 1.5 hours, the tech gets paid 1.5 hours even if he can do it in less time. The flip side is if it takes 2 hours he still gets paid 1.5 hours.....)