At the end of my rope, and bank account ! Bought a 1996 Collectors Ed. LT-1 coupe this summer and cannot get this slight vibration out of the car at highway speed. It's been to 2 Chevy dealers for a complete diagnosis ($) and every tire shop in town as well ($). The consensus seems to be the "tires". The fronts were replaced with BF's, road forced and new Bilstein shocks installed for the 1st effort. Still has a vibration after 60 or so. Then off to a dealer for a drivetrain inspection which turned up no bent or torqued short shafts or damaged u-joint etc...road test and still vibrates. Next - All new nittos and road forced with an alignment ...still have the same vibration. These wheels are from OE in Florida and are ZR-1 Aluminum polished 17 X 9.5 and 17 x 11.5 on the rear...NOW, I'm being told that a hub centric bushing might be needed but OE says the wheels are 70.7 mm hubs that don't need a bushing for a 70.3 shaft size. I'm running out of options and money................................... does anyone have a solution to my dilemma ? All the steering gear has been gone thru, something about a slip yoke was mentioned but the dealer said no on that. The car runs and looks great, never been abused, just turned 70k.

 

where is the vibration ? front or rear? if in front, you will feel it in the wheel. if in rear, through the seats.

I chased a vibration, turned out to be tires.

ALSO, the shops that were balancing the tires weren't getting the rims on perfectly. they seemed to not quite fit the machines. I also have OE Wheels. They would be balanced at one place, and you could take them somewhere else and they would be out of balance. 1 shop even said a rim was out of round. I put dial indicators on it and spun it and it ran true within a couple .001's. SO they weren't getting it to run true on their machine,

also, as a long shot, it could be a brake rotor out of balance.

 

^^^^Check the runout on them, tires too. Had that problem before. You can get ea wheel in the air and ck wheel runout...and watch the tread while spinning it
Got pissed and bought all new stuff.

A pinion bearing can do that, but will be more of a hum than anything. Vibrate wether youre on /.off the gas?

 

First things first: I wouldn't bet a dime on Nitto tires being round or well balanced. But you've got what you've got.

Second: Hubcentricity is not related to balance...at all. All the people that think a wheel depends on an interference fit with the hub to properly align itself and/or stay on the hub are just. plain. wrong. I'm so sick of seeing people get hung up on that and give people bad advice! The only thing a hubcentric fit does is make it easier to install the tire. The lugs are the only thing that locate the wheel on the hub, and their clamping force creates very high friction which is the only thing that hold the wheel in place. Over history there have probably been hundreds of millions of cars and truck produced and sold without hubcentric wheels. For example, I think every steel wheel ever made is not hubcentric. So don't bother with this - it's dumb. Besides, OE is correct that you basically already have a hubcentric fit.

I would pay close attention to drcook's advice. You need to be absolutely sure those OE wheels are straight. A roadforce balance can correct an imbalance, but it can't correct wheels or tires that aren't true. It also can't properly balance a wheel that isn't properly mounted on the machine. If all else fails, perhaps you can find someone local to you with a set of known-good wheels and tires and you can try them on your car. If the vibration disappears, it's definitely your rolling stock. I would make sure that all your ball joints and tie rod ends - front and back - are in good shape, too. But typically when you get a consistent vibration at a certain speed, regardless of throttle on or off, it's going to be rolling stock.

 

Thanks Matt, I'll look into all you've mentioned.

 

I went to a dealer that had the right machine the second time, ( wide wheels) I'll try the rotors next...something drilled maybe

 

both

 

Hi
As others have mentioned check the tires for being out of round, our firm suspension will make you feel anything that is not perfectly round.
Is quite common and with most road cars using soft suspension will not notice it, i have no trouble getting my wheels balanced spot on with the stick on weights.
Just jack the car and spin each wheel, check the tread of any high spots.
I have come across a few out of round tires in my time, had no problem getting them replaced free of charge.
Have found japaneese and korea make some quite good tires, have all been perfectly round and smooth without vibration.

I would also check your hubs and rotors are clear of corrosion and rust scale,
Did you get a 4 wheel alignment done when the new tires were fitted? is common for mechanics to not properly torque the offset camber bolts in rear suspension.
Look if any wheel has noticeable negative camber? if your tires are scrubbing toe in or out too much you will have vibration and saw tooth shape wear on your tread

Good luck

 

You may have a slightly out of round or bent rim

 

You might want to check your ujoints and wheel bearings. I would also check the harmonic balancer on the front of the engine. (I said CHECK not replace).

 

Tires are your problem always buy original equipment tires and as far as used rims never! I only buy Michelins for my daily drivers.Also the tire manufacture date a major problem if tire has been standing straight up in a warehouse! Mis match dates rubber run out changes all issues.

 

Ummm, you realize you can't buy the OE tires for a 96 Corvette anymore, right? And if you found some, their date of manufacture would be measured in decades, not years? And that Michelin (the only brand you use) never came OE on any C4? And that the OP may very well have purchased his wheels new?

 

Rims were bent on mine when I had that problem.

 

If I may chip 2 cents here, I have been chasing a vibration on my 1978 C3, 50-60 mph. I too had been to other shops, same vibration, I said tires or rims, shop said mechanical. We went round this for a yr. I changed out rear trailing arms, Drive shaft bal. tie rods, ball joint, steering box, Idler arm, upper control arm bushing, wheel bearings, power steering cylinder, new shocks. Swapped wheels around to find which one was bad. Finally got them to agree to balance each rim before the tire balance and place weights at 90 deg. from wheel weights. Rims were from . o5 oz. - 1.25 oz. tire .75 oz. -1.25 oz.....contacted rim dealer they sent me replacement rims .75 oz. or less. Traded tires for better quality. This improved the vibration a lot. I still have a vibration 50-60 vary slight but there just the same... So, now I am looking at non normal vibration areas, Spindle's ???? Brake disc.???
Wheel is bolted to hub, IF bearing tight then it can not move about, but if ever so slight, you would get a vibration, same with Brake disc,
Thoughts?? please.
DB

 

You generally won't get a vibration from a bad wheel bearing. When the car is sitting on the ground, it's weight is loading the bearings and that takes all the slack out. So the wheel is not really free to vibrate around, and there is no force causing it to do so. A vibration has to be caused by some kind of force, so the key is to find what that force is.

 

Agreed: but the wheel bears were replaced. I was not clear, The bearing sits on the spindle seat...the difference between the inner bearing surface and the spindle seat may be enough play to cause vibration at speed.

 

But that's still a theory that play - or lack of positive axial (not axle) location - causes vibrations. But that's not the case. A frisbee flying through the air has nothing at all to locate its axis, but if it is well balanced around its geometric center it will not vibrate at all. It's when a rotating object is not balanced around its center that it vibrates, because it's trying to establish an axis that is not co-located with the geometric center. And in fact the more securely that center point is fixed, the more easily the vibrations may be transmitted into whatever it is affixed to. So to put this back on the exact topic, something that is either not well balanced or not round is causing this vibration. The OP has to sort out what it is.

I should add one very slight possibility: brakes. If brake discs are badly warped they might cause a vibration as they move the sliding calipers in and out. But I would think you'd feel it terribly bad when actually braking. Maybe one rotor is really out of balance itself? Not sure how common that is.

 

I'll throw in one more possible and crazy issue. MANY years ago I had a similar issue with a vibration that could not be remedied. As a LOOOONG shot the alignment shop removed the tires to find a sheite load of WATER in the tires!!!!
Apparently the gas station I was using to fill my tires never drained the condensation out of their air pump. Water was being sprayed along with the air to the point that it put the tires out of balance.
To make it even worse, when the water froze, at speed it felt like i was driving over bricks. This was originally diagnosed as "flat spotting" because it became less as the tire warmed up.
So, it may not be your issue, but......

 

Hey..that is a good one. Never heard of it, but it could happen.

If I could get it on the road long enough to used the tires..

I have spoken with a person who's father had a 63....He had the same issue, he changed out every thing, finally, he said enough and put in a Rack & Pinon. No more vibration. Boils down to old tech in steering design....the play is caused by all the tire rods and other movable parts in the design, that are removed once a rack and pinon are is installed...come to think of it I had a 69 Jag 2+2 4.2 L NO vibration but it only had rack and pinon.....same for the old MGB....
With out a point of ref. like another 78 vett to compare with, I guess I was expecting it to be as I remembered from other cars.

 

Need to back up and see if the vibration is engine or drivetrain related. If you are running at the speed when vibration occurs, when you put the car in neutral with the engine at idle, does it continue vibrating or go away?