Tire Width

[g_boi240sx]

I Just bought a 240sx. I had a Honda civic, a nice one too. I traded my 17" rims for some 18"x7.5" rims, but I need 2 new tires. I was just wondering what the widest tires are that i could reasonably fit on these rims. The current tires are 215/35/zr18's. I know 225's will fit, but I don't know if I can go any wider.

[Beau]

Wider isn't always better. You sacrifice some wall stiffness when you start putting tires that are too wide on. Personally I wouldn't go any wider than 225's on those. I'm putting 225's on my 8.5" wide wheels.

[Nismo_Freak]

Incorrect, you can safely put a 245 on a 7.5" wheel... granted a 235 or a 225 is a wiser choice for performance. The additional width of the wheel does not effect the overall stiffness and lateral resistance of the sidewall itself.

[SmithSR]

I don't know about that. You're talking about what?

245/??-18

235/??-18

225/??-18

I suppose the aspect ratio would be important for telling you if the tire sizes in question would be an easy fit, a snug fit, or a bad fitment.

There is a general rule of thumb to keep in mind. The relaxed position of the tire's beads(the distance between the two beads) as the tire sits, unmounted, is basically an ideal measurement for how wide a wheel to use. You'll notice that many tire manufacturer's websites will list ideal rim widths with specific tire sizes. As irony would have it, the distance listed on various websites is always within ~.5inch of the relaxed position of the beads of the tire as it sits unmounted.

Not a bad place to start your research. "One can never have too much knowledge about tires."