I have an 89 c4 which I purchased a month ago. it was shaking from 30 mph and up so I had the front balanced but was told that the front passenger wheel was little bent. I had the rear wheels put on the front and the front on the rear. It still shakes a lot. what could be the problem?

 

You still have the bent wheel on the car in a different position? I suspect its the same wheel....

 

The bent wheel is now on the rear right but the steering wheel still shakes. I'm thinking that a big speed balance would help. This is an 89 with only 12700 miles so all is fairly new so everything under the car is still tight.

 

Bent is still bent regardless of the wheel position. Your IRS will not "dampen" the effect of a vibration.

Swap out the bent wheel and you will know if you have solved your problem within a 1/4 mile.

 

Why would the steering wheel shake if the bent wheel is on the rear?

 

Easy test, swap the bent wheel for the spare. If the shake doesnt stop or change you have eliminated the wheel.

I tend to agree with the OP that moving the known bent wheel to the rear should have changed how the car shakes. If it is still getting it in the steering wheel I'd start to suspect alignment, worn suspension component, possible flat spotted tires.

 

You're driving a Corvette. This is a very "in touch with the pavement" sort of vehicle, not a 91 Buick!! The vibration will transfer throughout the car. If you're convinced that its not the wheel, then another question also might be what caused the wheel to bend? Did that also "bend" something else in the front end? Put the spare or a good known wheel/tire on the car. If its gone, then its the wheel. If its not.... then have the front end and rear end checked for that matter..

 

A good tire shop should be able to spin the rims and check for wobble or damage.

Other things that 'could' affect this situation: something between the rim and hub preventing the rim from resting completely against the hub. The hub could be damaged also as could loose lug nuts.

I'd start with a tire shop if nothing is obvious.

 

As the other poster mentioned, it could be flat spotted tires as well. I have experienced that and you would be surprised how much of a vibration it could make at different speeds, especially higher speeds. It could be a combination of the rim and tires, etc.

 

..... How old are the tires ? Please don't let them be the originals .....

 

 

I think the front tires were the original. This car was from what I am told was stored since it only has just under 13 thousand miles.

 

..... There you go ! You just found out why your car is shaking ... 28 year old "May-Pops" ... you need to stop driving on those .....

 

I have 86 coupe and chased a vibration for a couple of years. The tires looked fine and even balanced perfectly. I went to three different tire shops. All three said the tires were fine. Finally after changing almost everything I could think of. My last option was the tires......Guess what, it was the tires. My stupidity. I now have new u-joints, bushings, driveshaft balanced with a new yoke, hub bearings and some more.

Your easiest try would be to get that bent rim off and go for a ride.

 

I've got a 89 that my dad bought used in 1994 that has a vibration as well even after a full balance. BFGoodrich Comp TA's. Its been garaged and tire shined and driven only about 20K miles since 1994. I know I hear old tires are dangerous but they looked in good shape. Just last weekend I noticed a hunk about the size of my little finger out of the sidewall on the LH Rear. I think it was dry rot. They still hold air. I'm rambling but regardless, I've got a new set of BFGoodrich V Tread A/S in the mail. I was stupid for waiting so long and glad it didnt blow on me. I hope it helps with the vibrations and feel too. i can tell the rubber is hard if I dig my fingernail into the tread. All this to say that even if they look great, 20 plus year old tires can crack the sidewall at any time. My problem was that it was hard to spend the money on the tires which looked good instead of elsewhere on the car. I agree swap the spare but based on my chunk missing for no reason, dont run 20 year old tires, Granted Goodyear Gatorbacks are really cool. Only ok for a pure show car thats not driven these days at 20 years plus old though. As for shakes or vibration such as mentioned, anybody ever set up a system to "troubleshoot" where the vibration is coming from? I"m not sure how this is normally done but I've been wondering if I could somehow set up a circuit with accelerometer and an oscilliocope and match up the hz (cycles per second) with RPM etc and back out the RPM of the wheel or driveshaft or engine to pinpoint where the vibration comes from. Not sure how to do this exactly but there is probably a logical way with the right equipment rather than guessing. Granted it would only get you so far to match up the frequency.

 

Thank you all. I ordered a new set of tires which will be installed Tuesday. Hopefully this will solve the problem. I will post the results.

 

You will be very surprised at how much of difference new tires will make. Nice soft rubber compound, good flex, etc. Plus you will not have to worry about an old sidewall blowing out, having the tire shred and taking out a quarter panel.

 

Just changed mine out a couple of months ago. Old ones didn't look 'bad' but at almost 10 years old, they were hard. That and some other changes I made to the car made a difference in it's handling and obviously safety.

 

If you drive the car more than 30 minutes in warm weather, does the shaking seem to go away?
THe steering racks on these cars suffer from "morning sickness"
the racks bypass fluid until the seals warm up and then start sealing.
The only fix is to change the rack.
If it has 13,000 miles on it, I would bet those seals are little hard rocks just like your tires.
Change out the bent wheel, get those tires installed, and take a sample of your power steering fluid. If the fluid is really dark, and not red anymore, you need a rack.
I bought a rebuilt at autozone, and they have a lifetime warranty.

I changed it twice since the first time.
In Phoenix, with the temps being so high, the racks jsut do not last.
but the next one is free. so was the last one.

 

Look at half shafts u-joints especially outers. Any sign of red dust means they are shot