squalsvette

hey fellas i have a 95 lt1 vert 6 speed with about 75000, i just started noticing on the highway after 50 miles an hour the steering wheel shakes, never did before. After hitting a bump the car will continue to shake thats why i think it could be the shocks, any ideas would be greatly appreciated......drive fast

94ragtop

Sounds like a tire balance problem. After a car sets for too long the tires sometimes can come unbalanced from getting too low of tire presure, Thats what happend to my front tires on my 94 drop top. This also happens often to the 4x4 off road tires (super swampers).

rick lambert

Or you could need an alignment.

theadmiral94

My vote would also be tire balance.

Maybe one of the wheel weights came off.

I like to balance tires every 12k miles, how long has it been since yours were rebalanced?

MBDiagMan

It is HIGHLY likely that this is a tire related problem. It COULD be imbalance but it also could be a tire or two that have developed a flat spot from setting for an extended period of time. If it is a flat spot, airing the tires to max pressure and driving about 20 miles or more will smooth them out some or maybe totally.

It is a very rare situation where alignment has an effect on vibration. Two other myths are shocks or worn front end parts causing a vibration. All of these things can exacerbate a vibration, but are not the cause. In almost all cases it is rotating parts that are the source of vibrations while all those other things can amplify vibrations.

If driving it an extended distance with fully inflated tires does not smooth out the vibration, find a shop with a GSP9700 Hunter machine with someone who KNOWS how to use it. This machine has a pressure roller that is used to analyze the tire for stiff spots as well as provide precise balance.

Good luck,

87vette

I had that problem and found out it was the rotors that were warped that caused this. After sending it back to the company and getting new ones... it cured the problem. I found that not only can rotors caused vibration when braking.. it can cause just the same upon accelerating or at hwy speeds. Mine only did it when I hit 50mph and up.

jdbxyz

If you find an answer please let me know. I'm not trying to hijack your thread, just want to share my experience. I have a 92 vert with the exact same problem. It's the shaking after hitting a bump that really concerns me. I've spent lots of time and money trying to track down the culprit, to no avail. I've done tires, wheels, shocks, rotors, ball joints, bearings, steering rack, tire rod ends (inner and outer). I've had several alignments (at different shops), balances, Hunter road force balance, and still the shake is there. I've read many other post with this problem, but not seen many solutions. There must be something specific to C4's that cause this problem and somebody has to have solved it before. As I said earlier, if you find the solution, please let me know. Thanks

resipsa

I bought my 95 coupe with 2300 miles on it in 12/95 (standard suspension) and it shook like crazy every time I hit a bump. This problem was much worse with the targa top removed. I replaced the OEM Bilsteins with Koni sport shocks and this change reduced the problem by about 90 percent. Since the C4 has a less than rigid body structure (the convertible is less rigid), the shaking after hitting a bump will not be completely eliminated, unless structural reinforcements are made to the chassis, as some of the shaking is the chassis structure itself.

MBDiagMan

A warped or partially glazed brake rotor will only cause vibration while the brakes are applied. BTW, if you spray dressing on your tires, make SURE that you cover the wheel so that none of it makes its way to the rotor. It can cause partial glazing which will feel like a warped rotor.

As far as shaking on bumps, I just finished making a camber brace for my 88 which eliminated MUCH of this. Since the frame is not free to flex at that point, however, it did result in a slightly firmer ride.

Have a great day,

jakers

My 94 coupe (top in or out) rode rough and shook seemingly at random on the highway at approximately 65 mph. It was so bad that I even pulled off the highway a few times thinking that I had a flat!? I have OEM ZR-1 replicas with Sumitomo tires that he previous owner put on the car. I did the following:

Replaced the shocks. (Improved quite a bit but not the fix)

Alignment (Nice but still shook diving into turns.)

"Speed balanced" the wheels and tires. (THAT DID IT!!) The shop that did it is owned by a former dirt track racer and the guy actually shaved my tires. He still added alot of weight so I think the combination of el cheapo tires and replica wheels threw the whole set up off.

Now it is smooth as silk up to triple digits.

grimmace

i have the same problem with my car...92 vert...21k...i had the original tires on the car still until this past summer....changed those and put on eagle f1's....didn't work...brought the car to a dealer with the hunter system and that didn't work...my local mechanic has said that he has seen a rim go out of round from sitting too long and suspects thats the problem...only shakes when going at highway speeds and the car feels like its falling apart whenever you hit a bump...I wish i knew what the answer was too!

87vette

I disagree. A warped rotor doesnt have to be braked in order to feel any vibration it can be just the opposite. In this case.. that was what happened to mine. It didnt pulsate when I braked.. only upon hitting 50mph etc.

grimmace

i took the advice of the board and decided to go with the hunter road force balance and it fixed all the problems i was having....no more shake in the steering wheel...the car feels tighter and takes bumps in the road better now too...thanks to everyone here

Gary