Originally Posted by my350z member

Hey man, I'm hoping you can help me out with a tire size thing i'm wondering about.

I'm new to this whole tire thing, so sorry if I sound like i don't know wtf i'm talking about. But I just purchased 2 245/35/18's i wanna put on my car. However, I still need to by 2 more tyres, i'm thinking 245/30/18's for the front?

I have an 06 base, so the rim sizes are 18x8 and 18x8.5 I did a little calculation and the rears would be off 7% while the fronts off 8%, so totall difference would only be 1%. would this work? tahnks for you time.

Originally Posted by JDMFairladyZ33

First and for most IMO you shouldn't have bought the 245/35/18s at all. Going by Bridgestone's application chart the 245/45/18 rears have a rolling diameter of 26.6" and the fronts are 25.9" for the 225/45/18s. With a 8.5 wide wheel in the back you should have gone with a 255/40/18 @ 26.1". 265/40/18s are actually closer to the stock diameter but you will be exceeding the 8.5 wheel width application safety threshold. So you have 245/35/18s which are around 24.7". You've basically dropped your rear height over two inches. I really do not like or advise this application in the rear or front. Also I think 245/30/18s are an offsize. I can't think of a tire brand off the top of my head at the moment that offers that size. I know Toyo, Nitto, and Falken do not carry that size to the best of my knowledge and they are some of the best tuner friendly companies in terms of tire sizing availability. If you are stuck with the 245/35/18 you may want to put them on the front (They are in range for 8" wheels) and get new rears. 245/40/18s in the back will be my first choice in trying to make this work even though width and proper rolling diameter wise the 255/40/18s will be the better fitment. You probably will run into trouble with the front/back height difference with the 255s. If the 245/35/18s still gives you trouble with the 245/40/18s in the rear then you'll know that the size is just not going to work. Then you can move the 245/40/18s to the front (which was the size you should have gotten in the first place if you were looking the increase sizing from stock on OEM wheels) and get 255/40/18s in the rear. The Z has to have either staggered front lower/rear higher or at least even. It can't have the rear lower. You understand what I am trying to tell you? You're kind of stuck between 2 sizes here. VDC problems are just one of your issues here. By completely changing the stock rolling diameter you are also messing with the ABS and speedometer. Each rotation, because it's a smaller diameter per revolution, will make the car think it's going faster than it really is. 4x4 owners run in this problem going the other way when they put larger tires on. The trucks end up going faster than what the speedometer reads.

Originally Posted by michaeljr6

the rear's are 8 too not 8.5...