eusgasm

I just ordered new replica wheels from Thunder Racing for my 2002 SS, the wheel are 18x10.5 O.E.Concepts and the offset is 58mm. well O.E. said it would work but it didn't. the tires I ordered are Nitto 555R 305 45R18. So now I need a spacer till I get a Moser rear built longer than stock (if it's possible??)

The question I have is will the combo fit without cutting or Knocking in anything?? after I get half inch spacers and longer studs for each side?

Thanks for any help and next time I'll ask on here before buying.

Injuneer

You are going to have a problem with the wheels, and an even bigger problem with the tires.

The backspace on that wheel calculates to 8.00". That will put the inner edge of the tire hard against the inner fender panel, and the jounce bumper bracket will catch on the inside of the wheel when you jack the car. A spacer will definitely be required.... maybe about 1/4". Spacers in the back, particularly with drag tires is not a good idea. Apparently you've already figured this out... not sure why Thunder Racing would even sell you the wheels without warning you.

Now the tires.... a 305/45-18 tire is 28.8" diameter.... well over 3" larger than the stock tire. You will require extensive body work, including cutting both the sheet metal at the front of the wheel opening, and taking as much as 2" off the leading edge of the bumper cover. The absolute largest tire you can fit without cutting up the fenders is 28.0", and even to fit 28.0" Hoosier QTP's I had to move the axle assembly back slightly to avoid contacting the sheet metal at the front of the wheel opening when the tire grew at 125+ MPH trap speeds.

And, that 28.8" tire will make you rear axle ratio feel like you reduced the numerical ratio by 11%.... if you were running 3.73's it will feel like you've dropped to 3.32's..... a set of 3.42's will feel like a 3.04. And even if you compensate by going to 4.10's or 4.30's, the heavier tires and the huge diameter could cost you a couple 1/10's and a couple MPH.

eusgasm

thanks for the information. I have looked every where for the actual backspace distance for the 02, can't find the numbers. I think I have to return some tires & wheels

It would be great and reduce the overall Wheel tire questions, if some would post them then we could all do the math and figure out what we need!

Can anyone give the actual backspacing for stock F-bodies I know the 2k's are different from the 97 & earlier?

Injuneer

To my knowledge, the rim widths, offsets and backspace have been the same since 1993. The only thing that has changed is the diameter of the rear axle hub, which prevents late model wheels from fitting on early model axles without some light sanding.

Stock 16x8's are 55mm offset, about 6-5/8" backspace.

Stock WS6/SS 17x9's are 55mm offset, about 7-1/8" backspace.

The largest backspace you can reasonably handle in the back is 7.93". That is what the 17x11 ZR1/Grand Sport offset wheels are, and depending on how wide a tire you put on the wheel, there is a chance you need some hammering of the inner fenders and cutting the protruding corner off the jounce bumper brackets. A 7.75" backspace will probably be the largest without any possibility of interferences.

In the front, with a 17" wheel, you can handle about a 7.40" backspace. Any more than that and you will be rubbing on the steering knuckle.

Backspace can be calculated if you know the width of the wheel and offset.... it isn't rocket science.

offset + (wheel width +1)/2 = approximate backspace

This is approximate, only because the "1" that is added to the width represents the width of the two "flanges" that retain the tire bead, and that number can vary from wheel to wheel.

Remember to convert the offset to inches, by dividing by 25.4

I've done numerous posts explaining the correct offsets for a wide vaiety of wheel widths.