Nissan 370Z Forum - View Single Post

tibor370 · 07-11-2021, 07:16 PM

Hi guys,

I'm going from 18" wheels to 19" wheels and I need some advice.

My car (used) came with 245/45 18" in the rear and 225/45 18" in the front. This works out to a 678mm diameter in the rear and 660mm diameter in the front, so a 2.7% difference in diameter.

From factory, the car had 245/45 18" in the rear and 225/50 18" in the front, which works out to a diameter of 678mm and 683mm respectively, so from factory the difference in diameter was just 0.7%.

And the other difference is that from factory, the diameter of the rear tires was smaller compared to front tires, whereas on my car it's the other way around, with the rear tires having an 18mm larger diameter than the front tires.

I'm really struggling with rear-end traction under heavy acceleration which is obviously going to be due to the fact that the rear tires are quite narrow at 245, but could the front/rear diameter difference be part of the issue as well?

The reason why I'm asking is because I bought the original 19" rays rims and they came with Michelin PS4 S tires on them - 255/35 front and 285/35 rear. The rear tires need to be replaced but the front tires still have some life left in them.

I want to replace the rear tires with 275/35 Michelin PS4 S and eventually the front tires with 245/40, so the factory 19" set-up. I want to go with stock tire sizes due to bureaucratic/regulatory reasons (I'm based in the EU).

But I'm wondering whether I could keep the 255/35 in the front for a little while and combine them with 275/35 in the rear?

The problem is that with this set-up, the difference in diameter would be 2.4% and like now on my 18s", the rear tire diameter would be larger than the diameter of the front tires. Whereas the factory 245/40 front + 275/35 rear 19" set-up has a diameter difference of just 0.3% with the rear tires having a smaller diameter than the front.

Am I correct in thinking that having larger diameter tires in the rear vs. the front is not ideal and means that the weight of the car is shifted more to the front, which could result in less rear-end traction under acceleration?

Should I just replace all 4 tires and go with 245/40 front + 275/35 rear and avoid running 255/35 in the front together with 275/35 in the rear due to the diameter difference? Or does it not make that much difference?

07-11-2021, 07:16 PM	#1 (permalink)
tibor370 Base Member Join Date: Jul 2019 Location: Europe Posts: 18 Drives: 2011 370z M6 Sport Rep Power: 6	Need some advice on tires Hi guys, I'm going from 18" wheels to 19" wheels and I need some advice. My car (used) came with 245/45 18" in the rear and 225/45 18" in the front. This works out to a 678mm diameter in the rear and 660mm diameter in the front, so a 2.7% difference in diameter. From factory, the car had 245/45 18" in the rear and 225/50 18" in the front, which works out to a diameter of 678mm and 683mm respectively, so from factory the difference in diameter was just 0.7%. And the other difference is that from factory, the diameter of the rear tires was smaller compared to front tires, whereas on my car it's the other way around, with the rear tires having an 18mm larger diameter than the front tires. I'm really struggling with rear-end traction under heavy acceleration which is obviously going to be due to the fact that the rear tires are quite narrow at 245, but could the front/rear diameter difference be part of the issue as well? The reason why I'm asking is because I bought the original 19" rays rims and they came with Michelin PS4 S tires on them - 255/35 front and 285/35 rear. The rear tires need to be replaced but the front tires still have some life left in them. I want to replace the rear tires with 275/35 Michelin PS4 S and eventually the front tires with 245/40, so the factory 19" set-up. I want to go with stock tire sizes due to bureaucratic/regulatory reasons (I'm based in the EU). But I'm wondering whether I could keep the 255/35 in the front for a little while and combine them with 275/35 in the rear? The problem is that with this set-up, the difference in diameter would be 2.4% and like now on my 18s", the rear tire diameter would be larger than the diameter of the front tires. Whereas the factory 245/40 front + 275/35 rear 19" set-up has a diameter difference of just 0.3% with the rear tires having a smaller diameter than the front. Am I correct in thinking that having larger diameter tires in the rear vs. the front is not ideal and means that the weight of the car is shifted more to the front, which could result in less rear-end traction under acceleration? Should I just replace all 4 tires and go with 245/40 front + 275/35 rear and avoid running 255/35 in the front together with 275/35 in the rear due to the diameter difference? Or does it not make that much difference?