I really need some help. I've posted before about a vibration I have in my 92 vert that occurs between 55 - 65 mph which can be felt in the steering wheel. Also, when I hit a bump, the front end seems to shimmy just a bit. To date I have replaced wheels, tires, shocks, steering rack, inner and outer tie rod ends, upper and lower ball joints (had the vibration before all of this work and is still the same now). Nothing was terribly sloppy, but the car does have 135K. Everything now in the front end is tight with no play in any direction. I have had 2 alignments and 2 traditional spin balances. Yesterday I had the tires road force balanced on a Hunter machine and the vibration is still there. The technician said the vibration felt like a wheel/tire issue and was as shocked as I was that it didn't go away after road force balancing since 3 of the tires had to be spun on the rims to balance properly. Does anyone have any insight. The wheels are chromed sawblades and they checked out with no bends or runout. The tires are Goodyear Eagle F1's and the road force balance showed no problem with out-of-round or flatspotting. Someone please help!

 

Did you check the hubs?

 

If you haven't check the wheel bearing/hub assembly for wear, you should do that. Jack the car up and grab the tire at the 12 o'clock and 6 o'clock positions and move in and out. If there is any movement, it can indicate worn bearings.

Do you have a way to swap wheels/tires with another Vette owner for a quick test drive? If there is an issue with the tires that cannot be seen (maybe cord separation??) that would be one way to eliminate your wheels and tires from being suspect.

Does the vibration stay the same or even get worse beyond 65? Did you check for any excessive runout with the wheels on the car? Also check the brake rotors for any runout. There's always a possibility that there is something between the hub flange and the inside of the rotor flange that is causing a wobble.

 

There should be a road force number that the hunter machine displays when it measures road force. If the number is 5 or .5 then the tire is so much out of round. The hunter machine can not compensate for it.

I had a shimmy/vibration issue and the tire guy told me that anything above .5 or 5 is BAD. He called tire rack and gave them the reading. Tire rack replaced the set. Problem solved.

I hope this helps.

 

what an excellent idea! Hope you can find someone to help you out with this.....

here is an interesting read on front end vibration:
http://www.puresearch.com/.knowledge...ou_to_Know.php

 

jdbxyz,

Where are you located? I happen to have a pair of Sawblades off my Vette right now while replacing the Rear Tir Rod ends. I am in Carrollton Texas. (DFW area)

Tim

 

AGREED, I was looking at the machine when mine were being done and the machine reffered to it as a bad tire if its throwing"X" pounds of force. One of mine was 57lbs. was swapped w/another new tire, then down to 6lbs =1/2 weight for balance after rim/tire match. How much weight did he put on to get them to balance?
That machine can test lateral runout and vertcal of a rim, was that checked, and what were the readings? O.E.M.s are supposed to be .001-.005 some after markets can be as far out as .015-.018 and that can be cause for problems. just a thought

 

Just currious, have you had the drive shaft out? Sometimes if it is put in 180 degrees from the original position a vibration can occur. Just a thought.

I had a similar symtom when I first bought my Vette. I bought new wheels and tires and it smoothed right out.

 

Take it to the speed where the problem is and kick it in neutral and let it coast to see if the problem goes away.
If the problem is no longer there, it is in engine or tranny.

How about brake rotor balance?

Tom Piper

 

Thanks to everyone for their comments an concern. I have checked hubs/bearings and there is no play at 12 and 6 (or 3 and 9). The rotors have been replaced but the car vibrated before and after the same. There is no wobble in the rims, I jacked up the front and put a dial indicator on the outer edge of the rim and saw less than .005" deflection. I don't know the numbers associated with the road force balance, but the tech said they took much less weight after the rims and tires were indexed. He also said that the machine would pick up any problem with the tire such as a separated band, etc. He said the rims and tires are fine. I have also switched front to back. I have replaced ujoints in the half shafts and one rear wheel bearing that was sloppy. The vibration is definately felt in the steering wheel and it occurs only between 55 and 65. Under 55 and over 65 there is no vibration. It also vibrates whether in gear or neutral. Everything points to tires or wheels but 3 shops have said they are fine. Also this is the second set of tires and wheels and both sets vibrated the same. I live in Wilmington Delaware and if anyone lives nearby and would allow me swap tires/wheels to see what happen I would be greatful. I once read a post about a wheel bearing causing this even when there was no play. Anyone have any ideas about that. I hate to put $600 worth of front hubs/bearings on the car as a guess. It just seems like it has to be a rotating mass in the front, I just can't find anything out of balance.

 

It's beginning to sound like an engine or tranny issue. Is there any vibration with the car stopped, tranny in neutral and the engine running at the RPM you see for the MPH where the vibration occurs? Probably around 1200-1400 RPM.

That could indicate a balance problem with a flywheel, pressure plate or even clutch disk (manual tranny) or a torque converter or flexplate (auto tranny).

Also check the motor mounts and tranny mount. If the motor or tranny is moving around, that could cause issues with excessive angle of the drive line (check the nuts and bolts holding the C-beam). Check all of the enging driven accessories (A/C compressor, alternator, PS pump, belt tensioner and idler for looseness.

 

Would engine/tranny issues show up in the steering wheel? It's an auto trans and the vibration is not RPM related if I downshift it will still vibrate at 55 -65 even though RPMs are higher. I also talked to a machine shop about the driveshaft and he did not think that was the problem since it vibrates both under power and coasting at 55 - 65 and the vibration is clearly in the steering wheel. I have been thinking more about wheel bearings. they are the only other rotating masses that have not been replaced/balanced. Is there any test other than 12 and 6 play that could show a problem. I do notice that one wheel freewheels easier than the other. Not that it's tight, it just will continue spinning less than other when off the ground. I thought that it was different amounts of brake drag, but tomorrow I will pull the pads and see if both wheels freewheel the same. If not, does anyone have a used hub assembly I could try? I have no trouble buying one if I know its bad. I just hate to keep throwing parts at it. I've done enough of that already.