jlutherva

What is the maximum spacer I can use on the rear wheels before I have to replace the Studs? I just mounted my new to me set of CCWs and I have interference with the UCAs in the rear.

geerookie

When you can't see threads showing past the lug nuts is a good rule of thumb.
With stock studs that is 3mm or 4mm spacer.

95jersey

I just bought a set of Pdfat 1/4" spacers. I spoke with them directly and they said 1/4" is the max.

jlutherva

Thanks for the quick response. I talked to the guys at CCW and they said that that wheel is the correct one for the C6ZO6 but that a minimal amount of interference with the car jacked up could occur with -2* of camber but that it should not be a problem.
Now I'm wondering if it's just the tow-in that is causing this weird side-to-side motion at very low speeds (> 1 mph). The back of the car wiggles back and forth just perceptively. If it's not the tow-in, then perhaps it's a defective tire?

Jim
Edit: I don't see this with the OEM wheels and Bridgestone tires.

jlutherva

There’s a number of problems; not just one. The first problem is the interference between the wheel and the UCA. I called CCW and they said that minor interference is possible with -2* camber on the rear but only when the suspension is fully un-weighted. With the suspension loaded, clearance is fine so I’m not too worried about that. The only place the suspension gets unloaded at VIR is on the back straight and with the Katech aero package, it’s not much at all. I’ll get a set of ¼” spacers from Phadt and that should resolve that minor clearance issue for the alignment spec I’m using. I sure don’t want to damage the UCA and have a stress riser on a component as important as that!

The second issue is the 1/8” toe-in on the rear makes the tires make strange noises at very low speeds. I'm guessing that this does not occur with treaded tires since the tread squirms to compensate. This, together with the interference above and the fact that I have an event this weekend has me totally freaked me out.

The third issue is the right rear tire clearance to the tub in the 9:00 position. There’s only about ¼” of clearance between the tire and the fender liner. I wonder how much the tire will grow at 150 mph and what's behind that part of the fender liner? I'll have it back up in the air tomorrow and will investigate.

The forth issue is a popping noise that I get while driving slow. I think it may be the emergency brake on the right side. I just installed the racing rotors in the rear and maybe that assembly didn’t go back together properly. If this is the problem, I don't understand why I didn't hear it before since I drove the Z over to ZIP Corvettes for the alignment.

More to follow.

Jim

gotjuice?

Popping noise might be in the rear brake rotors hitting the em. brake shield. Some aftermarket rotors tell you to grind the lip down a little.

jlutherva

The third and forth issue above are related. My race tires are 31-71-R18 S9D Michelin's and are very close to the inner fender. When the tire picks up gravel, it makes on heck of a noise. This does not occur with the street tires since the have more clearance. The popping noise with race tires at low speed is the tires compressing and releasing due to the toe-in.

Thanks for you comments. Time to pack for VIR for the first event of the season.

Jim