Today I put a set of 2001 Corvette wheels on my 98 Camaro.

The fronts are 17 x 8.5" with 245/45/ZR17 Goodyear Eagle F1 gs tires.

The rears are 18 x 9.5" with 275/40/ZR18 Goodyear Eagle F1 gs tires.

Fronts fit just fine. The rears rub pretty bad. I don't know the offset off the top of my head but it's whatever the stock offset is for those.

Inner fender well needs to be beaten in to avoid rubbing, which I will have to wait to do tomorrow at work.

My cars' suspension is all stock, stock de carbon shocks, and springs. Should I replace these? I heard wornout shocks and springs could lower the car almost an inch?

If it is the panhard rod how can I tell? If it needs to be replaced is UMI the best option?

Should I just get spacers? If so what size, what kind, and can I get them at advance auto or autozone?

 

The 2001 18x9.5" factory wheel has a 65mm offset. That gives it a 7.76" backspace, and although that puts the wheel a bit deep in the wheel well, its way less than the 7.93" backspace of the 17x11" ZR1/GS wheels. But there's a chance a fairly wide tire will rub a bit.

Spacers will help, but then you have the issue of whether you have enough thread engagement with the stock studs. Spacers aren't necessarilly the best solution on high HP setups, with sticky tires. It appears you have a V6 A4, so may not be a problem.

The panhard rod will be the cause only if the rear of the car is not correctly centered side-to-side over the rear axle. In that case, you would be able to measure from the inside edge of the tire to the subframe on each side, to determine if the dimension is the same on both sides. The rear being offset to one side would make one tire rub a lot more than the other. If the rear of the body is off-center, check the panhard rod and the mounting for damage, before buying an adjustable panhard rod to recenter it.

Weak springs may cause the rear of the car to sag, but moderately lowered 4th Gens usually don't have any more problems with the rear tires rubbing than stock ride height cars.

 

I have the same issue with my 95z28 and the 17 and 18's zo6 rims i have. The rears are 295/35/18 so they are a little bigger than what your running. I am pretty sure my issues are from the 120k mile bushings in my rear suspension.
I have already pounded out the wheel wells pretty good and they still rub.

I am pretty sure the offset is correct because I think i would of ruined the tires by now. Or they would be sticking out so far it would look like a low rider. They only rub the slightest bit, but still they rub.

A buddy of mine with 3 f bodies and 2 vettes thinks the same thing. I dont know for sure though, i may need a small spacer.

 

i have two rear spacers i just bought today, that i am not going to need. they are universal to fit any 5 x 4.75" bolt pattern and are only 1/4" thick so no need for replacement studs.

i beat my wheel well out pretty good today at work and no rubbing on the 40mph test drive. i wont know if there is any more rubbing until i hit the interstate tonight.

if you need the spacers they will prolly work for you since your tire setup is slightly bigger than mine. i will sell them for 30 bucks shipped. hit me up on a PM or email me at nktyson06@yahoo.com

 

The factory C5 Z06 wheels are a known problem in the back. They are 18x10.5" with a 58mm offset, giving them very close to an 8.0" backspace. That's even more the 11" wide ZR1's.

 

I just put a set of C5 wheels on my 96 Formula. The rears are 275/35/18 BFG Drag Radials. I don't have any problem with clearance.
here are a couple pics.