i have a 1991 z28. i don't know what size/type rear is in it but, i put on a set of 17X11's and 17X9.5's rims and tires on it i've also beefed up alot of the suspension on it. it has kybs adjustable shocks front and back. so anyway the problem is that when i hit a bump the right rear tires hitts the body which is strange because more weight is on the left side of the car. i think it's a weak spring. my problem is that i want to beef up the springs, but all the kits seem to lower the ride as well. this is a problem because the tires only sit a 1 1/2 to 2 inches below the body. also the rims and tires are way to expensive to get rid of so i have to find a way around that idea. anyone with any info please give me some ideas/partnumbers/ refrences. thank you to all who answer.

 

The main problem with the rear suspension is the use of a panhard bar. When the suspension moves down the rear end will shift to the right. This makes the tire closer to the fender. With stock wheel/tires, normally this will not rub. With wider wheel/tires, this will cause them to rub the lip of the fender. It is even worse if you lower the car. Most people will put in an adjustable panhard bar to allow them to shift the axle to the left to center the rear end. I had this right offset even with my stock parts. Once I put in the adjustable bar (Spohn part) I was able to recenter everything. I still hit the fender every so often if I hit a really bad dip. This is at stock hight with 17x9 with 275/40-17's. Hope this helps.

 

The adjustable panhard bar will probably be the fix.
You can also install "airsprings" also known as "airbags" like the Air Lift 1000. They install inside the rear coil springs. They increase spring rate (stiffness) as you increase the air pressure in them. They can be pressurized seperately so you can increase spring rate more on the right rear side to optimize drag launch. Then you can equallize them for normal street use.

 

i put the lakewood adjustable panhard rod on mine #20440. my rear was .29 degrees to the left. now it is centered and handles better.

 

Get some longer Jaunce spacers to keep the rear from bottoming out too much, SLP sells them, as do suspension companies, just measure yours and order longer ones.

Not sure if I spelled Jaunce right, but tha is how it sounds.