I am looking for some suggestions on the tire size for my 03 G35 6mt coupe, with brembo's. I have no modifications and I do not intend to modify. All of my tires are pretty bald and it is time that I replace them all around ... I was looking to go larger than the stock sizing that I have currently: 225/45/18 (front) and 245/45/18 (back).

I only intend to keep this car for another year so I am not looking to break the bank here, but it seems to me that the cost between same size tires versus larger tires is negligible. How big can I stand to go, stock (OEM 18" wheels, spacing, etc) without needing modification?

I have done some searches, but not finding clear answer. I was thinking about doing 245/40/18 on the front and 265/35/18 on the back.

 

Do NOT go 265/35 on the rear. That sidewall is the same as the 225/45 front wheels. You have to go 275/40 to get the same diameter as stock but have a wider tire. If you get 265/35 it will look dumb af.

Your front 245/40 idea is right on tho. That's the same diameter as stock front tires but 20mm wider.

I don't know how/if a 275 can fit on the stock wheel tho. I have 275/40 on a 9.5" wheel. Someone else chime in and tell him if a 275/40 will fit on an 8" wheel

 

Thanks man. I did some research off that and it looks like my stock wheels won't work with 275, unfortunately. I am now wondering about a 245/40/18 front with 255/40/18 rear .. ?

 

You'll still be losing decent diameter with 255/40. You could do 255/45 and it would actually be about 1.1% taller, but the only way to keep the same height is to do the 275/40. Losing diameter is not recommended at all unless you plan on lowering to close the wheel gap.

 

275 won't work on stock rims. You can do 265 but then have to find a front tire whose diameter doesn't throw off VDC as a result of the front to rear size difference... which is a bit tougher considering aspect ratios are always in gradients of 5 or more. Maybe keep the stock rear size and go 245/40/18 up front. I had that setup for a while but went back to 225/45/18 up front because the tire I wanted wasn't available in the 245/40/18 size. Unless you're doing aggressive racing I doubt you'll notice anything and your tires might actually last a bit longer with the stock size unless you've gone to aftermarket fully adjustable control arms with a more neutral alignment. I really like my Nitto Motivo tires on the G so far. 10x the tire my crappy Falken FK452's were. I wouldn't recommend Falken to anyone based on my experience with them, and the stock Michilin PIlotsports wore out fast, slipped a TON in the rain, and cost too much.

 

Feeling that you may be right and I may just go stock sizing all around. Looking at the BFGoodrich All-Seasons.