I have a 1985 Z-28 that is lowered 2" with Intrax springs(I think) and has SLP 17x9" wheels and 275/40/17 tires on it. The wheels have the backspacing for a 4th gen F-body. I have 2" bolt on spacers front/back.The car at high speeds I'd say 65mph and faster the car has a nasty vibration come from the rear of the car. I recently had a shop work on my car and he said it was the wheels spacers causing the vibration. He said the wheels are balanced and the drivesahft checks out okay. He put the car on a dyno and said the rear wheels were wobbling so he sanded the hubs on the rear rotors and also the spacers to knock off any rust or debris that might throw them off. He put it back on the dyno and said they still wobble but they are better than before. I am not thinking I have a bent axle(s) .

My first question is has anybody had any problem running wheel spacers on their car? Vibrations,shakes,wobbles,shimmying etc?

I was told by a friend he heard that wheel spacers can cause the axles to bend due to you are now extending the axles outward and putting more stress on the axles than there are built for. Is this true?

My second question is about shocks. Since my car is lowered 2" and still has stock length shocks I believe it cause my left rear shock to fail early. Is there any companies that make shocks for lowered F-bodies?

Sorry for the long post.Any help would be appreciated.Thanks Damien

 

You have a couple of different things going on here that may or may not be related. You've also been fed some pretty big cow patties.

First the lowering springs are way too low and too soft and your shocks failed do to bottoming out constantly in the bottom of their range. Get rid of the intrax springs. Every car I've ever looked at that has ran them for a while has beaten the bump stops off the car.

The vibration could be caused by a few things, could be the pinion angle is way off being lowered as far as it is. Also could be a bent axle, wheel or incorrectly machined spacer. A quick check would be to jack the rear end off the ground and use a dial guage to see what the runout is at the wheel, then at the spacer and then on to the axle flange. You could also just make a pointer of some kind and just visually look for some wobble from the rim. I wouldn't imediately jump to the conclusion that it's the wheel spacers as it would be very hard if not impossible to machine them crooked as they are cut on a lathe. Most mechanics cringe when they see them because they think they are just like slide on spacers.

Your friend is wrong and right in thinking that the spacers put more stress on the axle. The center line of the wheel is the only thing that matters, think of the center line as where the weight of the car is going to act through. WIth the spacers you are returning the center line back to stock, it would actually be harder on the axles without the spacers. He's right in a round about kind of way because most of the time you use spacers to fit wider wheels which will increase your cornering ability which in turn puts more stress on your axles..........which is the goal.

A pure ancedotal example is my brothers camaro always had a wicked vibration at 70 mph. We tried different tires, wheels, u-joints, shocks you name it. It only quit when we replaced the rear end. He runs 2" cheapy china spacers with no problems at all.