2000 Camaro SS Lowering Kit Quesiton

I have a 2000 Camaro SS and I have the new c6 z06 rims with the tire size of 275/35R18. How much can I lower my car before the tires rub??? Thanks

I have 17x11 ZR1s, 315 tires. I cut 1 1/4 coils off my springs and I rubbed (27" to top of fenders) a bit. Don't know if this helps...