vibration on my 1994

[bsmurf1962]

Great Site...

This is my first Vette.. I want to learn as much as I can.
This site seems to be the place ...Thanks..

? - My car rides nice on flat highway's under 70 mph BUT
if I go above 70mph the front end rattle's or vibrates.
*would this be my shocks..?

:confused

 

[LarryBible]

I really expect that it is due to imbalanced wheels.

The most common situation that causes this is that many tire stores do not want to put weights on the outside of aluminum wheels. This is probably because of customers getting irritated because their wheels have been scratched.

So, many tire stores simply set their machine on static and use weights on the inboard wheel lip only. This prevents the wheel from hopping up and down, but it makes the wheel "wobble." The only way to cure this is set the machine for a Dynamic balance and use weights inboard AND outboard. If you don't want to scratch the wheel, simply use tape weights on the inside diameter of the wheel as far toward the outboard edge of the wheel as possible.

I suggest that you go look at the wheels and see if they have weights on the outside of the wheels. If they don't, look behind the spokes and see if you find any tape weights. If there are no weights outboard, I am sure that this is your problem. Find someone that will balance them correctly, and I can almost guarantee that your vibration will disappear.

I got so frustrated with the tire stores and the fights I had with them trying to get them to do this right, that I bought my own computer balancer. It does a great job!

Have a great day,

 

[HOWSER]

I would also assume either an out of balance wheel or tire with wear. On certain tire brands, and maybe others mave noticed this too, after the car sits for a while or even on cold morning the tire actually develops a small flat spot. It will dissapear after warm up. This has happened to me a few times...vibrations around 70, but it dissapears after maybe 5 miles.

Does your car always do this after 70? I'd recommend taking it to the tire shop and have then inspect it. It should be a simple task!

Good luck.

Eric

 

[bsmurf1962]

All the Time,
The car has 40k miles so maybe I should check the Air pressure on the tires. I just wanted to check with this group to if it was my shocks...Looks like its not.. So I will do some investigating on the tires to see if there are weights...like larry suggested.

Thanks All

 

[c4ever]

bsmurf,
I highly recommend going to a place that uses the Hunter 9700 machine. It's the only way as far as I'm concerned to get a true balance. I had the same issue on the 85 and the Hunter was the only unit that could solve the problem.
Good Luck

Carlo

 

[Vettelt193]

The hunter is the one that road tests the tire, and spins the rim and tire alone first to find the best way to mount the tire?? if this is the one I am thinking about, it is definitely worth the extra cost to have the tires balanced... perfect every time, and also no weights on the outside... My Dad has a 98 pace car, the factory replaced the wheels under warrantee, and I asked the tech to balance the wheels with weights only on the inside (couldn't damage those yellow wheels!)... it shook like crazy (he has done the same with my vette, not runflat tires, with excellent results) when he replaced the tires, they had the new balancing machine and it has no weights, but is perfectly smooth now.

 

[LarryBible]

The Hunter GSP9700 is the finest tire machine ever put inside a shop. However, in 95 cases out of 100, the 9700 is not necessary to get a smoothly balanced tire. In most cases all that is required is any decent computerized balancer in good working order, an operator with an IQ above 70 and more importantly an operator with an attitude of getting the job done right and willing to take the time to do it. Most especially the operator MUST set the machine for DYNAMIC balance, not static.

I would give you a 95% chance that if your car was in my driveway, I could pull off all four wheels and run them up on my fifteen year old Coats 1001 balancer, and afterwards you could run it to 150MPH with no vibration.

Where the GSP9700 comes in is when you have a tire with excessive road force variation (stiff spots). The 9700 has a pressure roller that presses against the tire to measure the stiff spots and propose the solution, which sometimes is to get another tire. As a previous poster said, it also sometimes offers the solution of telling you where to orient the tire on the wheel.

To learn more about the 9700, go to: www.gsp9700.com. Believe it or not I'm not your Hunter salesmen, it's just that I recently went through all this and learned alot about tire construction and balancing in the process.

BTW, I fully expect that the reason there were no weights on the outside is that they taped just behind the spokes. The 9700, and many other recently developed balancers, actually are smart enough to hide the tape behind the spokes. I promise you they did not have ONLY weights on the inboard wheel lip.

Good luck,

 

[Redbob]

Like someone else said, the most important thing is to get a tire tech with an IQ above room temperature;
altogether too many will put balance weights on either the inside or the outside ONLY.
Another common failing is to mis-locate the weights, and then not re-check the balance by giving the wheel a final spin after installing both inner and outer weights.
If your tire store won't let you watch while the work is being done, go somewhere else that will.
And a big name out front like "Goodyear" is no guarantee of getting the work done right.
Good luck!
- R

 

[Vettelt193]

weights don't fit behind the spokes on the front wheels of C5's, there isn't enough clearance to get by the caliper. I guarantee that there are only weights on the iside of all four wheels on my Dad's '98 pace car. I don't know what my Vette tech does, but he can take a normal balance machine with normal tires (non-runflat) and balance them perfectly to over 120 MPH with no vibration (i am sure you could go faster than that too)... He doesn't use stick on weights or anything on the outside, only inside weights... He is one of the beset Vette techs there is, but I still can't figure out his technique....
-Now that he has the new balance machine, he can do the run-flats like that too... Wheels look much better without weights on them, especially if they never had them in the first place!

 

[Redbob]

You can't dynamically balance wheel and tire assemblies with weights at one lip (inside or outside) only.
Unless that particular wheel has imbalance in the plane of the lip only.
It's not physically possible.
- R

 

[Vettelt193]

It has been done, I don't know how, it may go against the regular rules of physics, but I am sure there is some way to explain it... Next time I see my vette tech I will ask him how he does it

 

[Gorgon]

Vettelt193, do you know of any good shops here in Melbourne to take the vette to? Where does your father go to get work done on his? I need a rear tire or two on the 95 and am not sure who to trust with it.

Thanks.

 

[86targa]

the very best way for any alloy is to use the stick on weights that allows them to be put back away from lip. Computer balance on corvette wheels usually isnt worth a crap because the rim is so wide with large offset. Ive had many wheels on my corvettes and my ferrari that were redone and redone with no acceptable result. Ive found the only way to get them super smooth at even very high speed is spun balanced on the car. There hard to find, but they jack the car wheel off the ground, then slide the machine under the tire and spin it to hiway speed. An experienced tech just can tell by feel on the fender/hood what to do. It takes a while because its trial and error. He keeps adjusting wieght and position of weight by using tape. when its perfectly smooth running, they take the paper off the back and attach the wieght there. Ive had both my cars done now. The corvette just got new ZR wheels and tires and they shook like a dump truck-cured it great. My ferrari has been done now for 2 years without rebalance and still smooth as glass past (way past) 100 mph. Its expensive at about $20 per wheel, but worth it to me.

 

[Redbob]

It has been done, I don't know how, it may go against the regular rules of physics, but I am sure there is some way to explain it... Next time I see my vette tech I will ask him how he does it

Beware any solution that goes "against the regular rules of physics" - those are the rules that make our cars run. Quantum physics doesn't apply here, and phasers don't work yet, either.
Trust me on this one - vibrations is the field that I have my degrees in.
And if you're interested, I can recommend some excellent texts, starting with Wm. T. Thomson's "Theory of Vibration", page 52.
Regards,
- R

 

[LarryBible]

Redbob,

Thanks a million for the book reference! I am also an engineer, though electrical, but I really get into such geeky stuff.

Everyone,

The only way that a wheel can be balanced vibration free on a car with such a nimble suspension as a Vette is a dynamic balance. To dynamically balance weights must be used on two planes. It is EXTREMELY rare to spin up a tire and have the balancer indicate the need of weight on only one side. When this does happen, you have a 50% chance of requiring the weight on the inside. If I ever spin up FOUR wheels this way on the same car, I will MOST DEFINITELY GO OUT AND BUY A LOTTERY TICKET!

I expect that the wheels with weights only on the inside lip have weights on the inside indentation of the spokes or some such. I am anxious to hear what the tech says he did.

Have a great day,

 

[timmb001]

I am getting a small vibration at between 60-70 mph. aftyer reading all the above posts about having the tires properly balanced - can anyone suggest a place in San Diego, CA for a four whell alignment and a dynamic balance?

 

[jsinga]

Look at the hunter.com site and find a location with the GSP9700 machine.
One more thought, if the tires are balanced and you still can't get rid of the vibration on cars with plenty of age or over 75K miles take a close look at the rear halfshaft u-joints. They will cause a high speed vibration.

JS

 

[Eagle85C4]

Redbob

Last year when I had the SZ-50's put on the car I had them remove the weights from the outside of the tire and place them inside. They run fine....no vibration up to 125...

So it can be done and it works ok...



And I did win a lottery in Indiana....

 

[Redbob]

You're fortunate.
It can be done, if there is only a single-plane imbalance and if the tire balancer can by luck or by a series of trials find that plane and locate the balance weights in it.

In the more general case, however, I wouldn't rely on that method.

Regards.
R

 

[Eagle85C4]

I stood there and watched...they spun the tire up....hammered the weights on the backside and run it up again....this time 0's across the board...next tire. There is no luck involved as well as very little skill, the machine tells you where to place the weights.