Tires and Rims need some advice

[ChrisinGermany]

I onw a 2002 Z28 I want to put 18" all arround 295 in the back and 275 up front want to go as wide as I can anyone know what kind of spacing I will need or if I can go wider without rubbing any thoughts would be appreciated.

[Injuneer]

You can comfortably fit a 9.5" wide wheel in the front. You need an offset in the range of 45 - 56mm. With that wheel, you would typically run a 275/35-18 or 285/35-18 tire. Both those tires would be within 1/4" of the stock tire diameter.

In the back you can fit an 11.0" wide wheel, with possible modifications to the body. You would use an 18x10.5" or 18x11.0" wheel with an offset in the 45-50mm range. That wheel would accept a 315/30-18 tire. You will probably have some rubbing with that combo. Typical mods are 1) light hammering of the inner fenders, 2) rolling the "lip" of the wheel opening that protrudes horizontally into the wheel well, 3) cutting the protruding edge of the jounce bumper bracket and/or 4) recentering the body over the rear axle with an adjustable panhard rod.

If you used the 18x10.5" in the back, with a 295/35-18 tire, you would probably eliminate most of the need for mods. That tire will be about 2% larger than stock, requiring recalibration of the speedometer/odometer in the PCM.

There are some Auto-X fanatics running 17x11" wheels on all 4 corners. The fronts end up a bit toward the outside of the fender.

The benefits of using an 18" wheel/tire combo on the solid rear axle F-Body are probably limited. Large diameter wheels and very thin sidewall tires work better with independant rear suspension setups, because the suspension has the range of motion that allows the narrow sidewall to compy with the road contour and body motion more fully.