I have a completely bone stock ‘02 Z28 that has the single spoke SS (275/40 R17s) on all round right now. I’m unable to find a straight-forward answer. The car is not for track use, drag nor autocross. Strictly a street car. I understand that all 315s aren’t the same. I’d like to run a 315 in the back on and 18x11. What is the biggest tire I can run front and back with ZERO modification? No BFH, no fender rolling although I’m not opposed to it, no narrowing, no tubs, nothing. Just directly bolt on. Front and back. Full rim/tire/offset/backspacing answers would be appreciated.

 

285/40/17 if you want the same size front & rear on stock 17" wheels.

 

You just reminded me. I forgot the important part. I want to run an 18x11 in the rear with a 315 tire. I don’t need to run square but somewhat close would be cool.

 

285/40/17 will fit in the rear with no issues on a stock 9" wide wheel with factory offset of +50mm (and I've also used this size on the rear without problems on an aftermarket 17x9.5" wheel with a +46mm offset), but it will sometimes catch on the bumper cover lip (where it wraps around into the wheel well) up front on the 17x9"/+50mm offset - and it will definitely catch, hard, on this lip with a 17x9.5"/+46mm offset (I tested this with mine many years ago). Ride height, suspension condition, and minor variances from car to car and tire brand to tire brand will determine if this is an issue or not up front with the stock wheel & tire sizing. To be honest, even the stock 275/40/17 size will sometimes lightly rub in the center of the wheel well liner under full lock (again, depending on all the aforementioned factors), as mine has with certain tires in this size on both the 17x9"/+50mm and also the 17x9.5"/+46mm offset, but that size shouldn't ever catch on the bumper cover lip like the 285/40 can.

 

Forgot to mention I’m trying to run a 18x11 on a 315 tire in the rear.

 

well for starters you're not going to be able to run a 315 on the rear without rolling fenders and hammering out the inner wheel well. if you don't want to modify anything don't go over a 275 tire, there's tons of threads with all that info if you search, including the sticky that is at the top of the page. the front has more room than the rear, i am running 295/35/18 tires on 18x10.5 +50mm offset wheels on all 4 corners of my car, and there are plenty of guys that have run 315's on the front.

https://ls1tech.com/forums/wheels-ti...must-read.html

 

I'm running 315's in the front & rear on a 18x11 each with a +40mm offset.

Fronts bolted right up, no mods.

Rears I had to grind bumpstops and roll fenders a bit.

Here's my thread for more info:
https://ls1tech.com/forums/wheels-ti...8x11-pics.html