Finally had someone follow me, and confirm that my driver's side rear tire is bouncing at speeds over 60 mph. Tires have been balanced, driveshaft has been balanced, new u-joints, and new axles. I've posted this before and was pointed to look at the yoke, would this really cause the tire to go up and down? Also, car is a peg-leg, and has new shocks. Any ideas?

 

almost forgot, bearings and seals in rear, as well as carrier bearings are new as well.

 

Separated tire.

Swap left & right and see if it follows the wheel. If it does, break the rear tires and wheels down and swap the tires on the wheels and see if it still follows the tire.

 

It vibrates up on jackstands, I wouldn't think a split tire would cause problems when its off the ground, would it???

 

If you mean that the tire is visibly not round even when it has no load on it, then ...... the tire is not round. By definition, any shape other than "round" will be percieved as a vibration.

The usual thing that causes a tire not to be round is a belt eparation. That is a condition where the belts shift inside the tire casing, creating a lump in the tire; sometimes they split the inner lining of the casing, such that air gets in there and makes a blister sort of thing on top of the lumpy belts. There is no cure for a separated tire, except to install a non-separated one in its place.

 

I always thought that when the tire was phisically bouncing off the road, it was a worn shock??? Sure you didnt get a bad one??

 

If the tire ran perfectly smooth, there'd be no bouncing for the shock to damp; at least not until the tire hit a bump.

The ONLY things that will cause a tire to appear out of round on jack stands is a non-round tire; or a bent wheel; or a bent axle. I'm giving him the benefit of the doubt that his new axles are straight and that whoever balanced the tires at least looked at the wheel while it was spinning to see if it was round.... although these days, you never know, it's getting hard to hire good help.

 

No, no, that's not what I meant. When you run the car on jackstands, the wheels wants to go up and down once the speedo reads 60mph. The wheel and tire look perfect. It is not out of round, believe me. Midas looked at them as well and didn't find anything wrong. My question was, eventhough the tire looks perfect, would separated belts make the tire to appear out of balance with the rearend up in the air?

 

Yes. Separated belts make the tire to be not round. What it looks like sitting still doesn't matter, and it doesn't matter if the tire is new.

Try what I told you to do. That will narrow it down to the tire, the wheel, or the rear end.

 

you could have a bent axle shaft , that hapen to me once swap your tires from side to side and check if it still bounces on the left side or the right , also check your rim. Good luck finding your vibration.

 

My first guess is a bad tire as well, since you said you have new axles. You may not be able to see the problem on the tire. About 8 months ago it happened to my wifes 95 cutlass. Tire shop said " the tire is fine, we rebalanced and it should be fine" It was on the front. At speed the steering wheel would shake really bad. I had them take deflate the tire, you could then see the slipped belt Took the tire off the wheel and you could also see the problem inside the tire. Something you might try anyway.

 

Thanks guys, I appreciate it. When I first got the car, I did swap the tires from left to right, and still had the vibration/bouncing on the driver's side. But since then I swapped the shocks, axles, driveshaft, rearend guts, etc. I think it may have been a combination of those things, because it has gotten better, so I definitely need to go back and swap the tires again since I've changed all that. Sometimes you just need to talk this stuff through, and since I don't work with any car guys, all of you have to listen to me. Thanks again.

 

Well, found the problem. Each of my rear tires was full of fix-a-flat. The prior owner had used it and not told me. Two tire shops missed it. It's smoooooth now. Who would have thought. All that work, and it was fix-a-flat.....

 

Odd you would think that balancing the tires at first would have gotten rid of it. BTW fix a flat isn't normally a problem if you drive 20 miles or so after you put it in.