I have 8.5 inch x18 wheels in the front with 245-40/18 Mich Pilot Sport tires and 9.5 inch x 18 wheels in the rear with 275-40/18 Mich. Pilot Sport tires. The rear tire tread is getting low and I was wondering if I should go with 265-40/18 for the rear when I replace them. I will keep the fronts as they are now and re-use my 9.5 x 18 wheels in the rear. I thought the 245 Front and - 265 Rear may be a better combination / closer to what came with my 2004 350Z Enthusiast which was 225-50/17 in the front and 235-50/17 in the rear on OEM wheels. What do you think?

 

255/40 and 275/40 combo is dang near perfect

 

If I remember correctly, the S-Tune Z33s with the optional LMGT4s came with 245/275 tires. I wouldn't base my tire purchase off the 2004 Z tire specs--those tire sizes are comically narrow.

 

I am running 245/40-18 and 275/40-18. I like the handling. This setup has slight understeer.

 

I was thinking at times it seems the 275-40/18 is tall for the rear (diameter of 26.7). I believe the Nismo 350z uses 265-35/19 in the rear and this tire size diameter is smaller than 275-40/18 and the diameter is 26.3, the same as the 235-50/17. Anyway, just wondering if the handling is improved any. Maybe I'm just splitting straws at this point though.

 

Most lasting handling changes are based more on suspension setup changes (swaybars, springs and camber/toe settings), rather than slight changes in tire sizes. Certainly, you need to keep wheel/tire diameters in mind to prevent VDC problems, and newer tires will generally have better stick, but the OP really is "splitting hairs" in this discussion.

 

Yep, true, 235/50-17 is 26.25"

But If you compare OE 18" sizes...

Stock Reference 245/45-18: 26.68"

To your choices:
265/40-18: 26.35"
275/40-18: 26.66"

Yes, the 265 is closer to an OE 17" but the 275 is spot on compared to OE 18". In the end, a 275 gives "better ultimate grip" simply due to size on proper wheel width (as yours is). But in actuality, there's not a lot of difference in performance (unless you track the car then the extra 10mm MIGHT make a bit of difference overall). And the cars are all calibrated the same between trim levels (17-19" wheels) so long as the 3% F-R delta is maintained for VDC/TCS. The 245/275 combo keeps the VDC happy and with negligible speedo error.

Bottom line: You're fine with either one. I'd give the 275 the edge just by tire selection choice being a tad better.

 

Thanks!

 

Will a 255/40-18 tire fit OK in the front on a 8.5 inch wheel that has a 25 offset?

 

Yes.

A 255 is right in the edge of “acceptance” on an 8.5 before performance gains start to diminish (even though you can physically mount larger sizes). But yes, fit should be no issue.

 

OK, great, thanks. Now I'm wondering before I pull the trigger to order new tires, should I go with the 255/40-18 or stick with a 245/40-18 in the front while running 275/40-18 in the rear? Again my 18" wheel on the front has a 25 offset. My rear wheels have a 22 offset.

 

You are good with either the 245/40-18” or 255/40-18” front tires with your 275/40-18” rear tires. The 245/40-18” are closer to stock diameter, but 255/40-18” is within specification with the 275/40-18” rears.

One thing you may not like is the 25 mm offset on your front wheels. I have an 18x8.5” wheel with 25mm offset, and it is a little bit too “tucked” inside the fender. An 18x8.5” wheel with 15mm offset would have been a better choice for me.

 

Thanks!

 

So, no rubbing with a 255/40-18 on the 25 offset wheel? my 350z is at OEM/stock height. And I was wondering about the handling on curves. Is the 255/40-18 better than the 245/40-18 on the 8.5 inch wheels?

 

You won't experience any rubbing with either the 245 or 255 tire on an 18x8.5" wheel with 25mm offset. And... 10mm (the difference between the 245 and 255 tire) is minimal. You probably won't notice any difference.

 

I'd buy these, PILOT® SUPER SPORT 245/40ZR18 and these, PILOT® SUPER SPORT 275/40ZR18.

 

OK thanks for everyone's help. I'll stick to the 245-40/18 and 275-40/18 Mich Pilot Sport.

 

If you go with these or any other brand name tires (Conti, Toyo, Bridgestone, etc.), you might also want to check out simpletire.com. They run some pretty good sales (and I think they have a Memorial Day sale going on currently) that can cut 10-15% off tire prices and with free delivery. I've ordered 3-4 sets from them (for various cars) in the last year or two. Fast delivery, great prices. Just as example, I bought a set of Toyo Proxes 1 (the uber sticky street tires), 255/285-19 set for about $750 (reg. price around $1300).

Didn't look at Michelin but a set of Continental Extreme Contacts in those sizes was $718. And I love those tires on my non-but-way-faster-than-Z car! Been running various Continentals for 30 years on various cars and have never had a set I was disappointed with. Just more datapoints.