Wheel/Tire Sizing Experts? 245/40 on a 7.5" Wide Rim?

[Turbobink]

I just upgraded from the OEM Gen4 16" rims to 18 x 7.5s off an ’03 Infiniti M45. The original equipment Infiniti tire on this rim is a 235/45/18.

I'd like to run a wider tire but still stay reasonable as far as a change from the OEM overall diameter. The tire I’ve found to be most desirable to me is a 245/40/18.

In shopping for that size tire (245/40/18) I'm finding that the acceptable rim width is 8.0” to 9.0”.

What’s got me a little perplexed is the fact that in looking at some of the application tables for various tires, some state that the acceptable rim width for a 235/45/18 (the OEM size) is also 8.0” to 9.0”.

That being said and knowing that, in fact, the manufacturer put a 235/45/18 tire on a 7.5” wide rim, would everyone think it would be safe to install a 245/40/18 tire on a 7.5” wide rim?

[BLACKonBLACK98]

i think it would be safe, but i wouldn't do it. 235 is pretty fat for a 7.5" by my standards (but i'm running 235 on a 9.5 so...).

i would just stick with 235/45.

[LeX]

i would stick with 235s. 235 40 or 235 45

[essential1]

I'm running 245/45 on an 18x7.5 wheel. I got way too much meat on the wheels. Go with 235/40.

[NmexMAX]

It's been done before, but I wouldn't do it, so

[irish44j]

stick with your current size.

btw, different tires from different companies have different specs depending on sidewall construction and stiffness - hence why some will fit that size and others say they won't.

[LudaTej]

im pretty sure it would be safe but juss like everybody else has said ud be better off stickin with the 235s... it's wide enough as it is...

[nowicki13]

I would NOT put that tire on a 7.5" rim. As the ratio increase (40 to 45) you get more leeway on the width of a rim you use. So you can use a 235 on a 7.5" rim in a 45 ratio, but shouldn't with a 40 ratio. Even more so with a wider 245mm tire. If you had a 50 ratio, you might be able to stick it on a 7.5" rim, but I wouldn't put a 40 on that rim. Safety and Specs aside, it wouldn't look good at all. You can put a 235/45+ or a 225 in any ratio on that 7.5" rim. You need an 8" rim for a 245/40. Keep in mind -wider tires are better traction, but lower gas mileage.

[tibal]

I just purchased some OEM 350Z Touring V.1 18's for the max. I was planning on getting some 225/45/18's for the front, and 245/45/18's for the back because of the offsets, should i instead get 235/45/18's for the back as you told turbobink?

[nowicki13]

What is the width of those rear rims? If it's 8 or 8.5" than either the 235 or 245 will probably fit. He was trying to install a 245/40/18 tire on a 7.5” wide rim -a wider tire, and smaller rim than your combination. FYI - a 225/45/18 is 26" diameter, a 235/45/18 is 26.5" diameter, and a 245/45/18 is 26.7" diameter. Your back wheel will be slightly larger than your front regardless.

[MrDicks95SE]

dont do it. stick with 235/40-18.

[Digitized]

I'm running 225/40R18.. 235 would be maximum I would go..