Tire Question

B'ham Jeeper · #1 (**permalink**) 09-12-2007, 09:18 PM

Ok I have a "newbie" question. I have 18" wheels but I see alot of people talking about 33" tires. What size tires do I have? And what size tires will fit my wheels?

Thanks...

currupt4130 · #2 (**permalink**) 09-12-2007, 10:18 PM

Look on the sidewall. You have 18" rims, you have a tire size that fits onto an 18" rim. Probably metric if they're factory.

redrooster · #3 (**permalink**) 09-13-2007, 07:02 PM

Your wheel has an outside diameter of 18". When people say 33" tires they are talking about the diameter of the tire.
Example: say your Jeep has 235/70/18 tires. 235 is the width of the tire in millimeters. 70 is the aspect ratio meaning that the sidewall is 70% as tall as the tire is wide. 18 means that it is designed for an 18" wheel.
If you want to convert the tire height to inches, it goes like this: 235mm x .70=164.5mm sidewall height. Convert that to inches: 164.5/25.4=6.47 (we'll round to 6.5") This means your sidewall is 6.5" tall. To get the overall height of the tire you add top sidewall plus rim plus bottom sidewall, 6.5+18+6.5= 31"
An Auburn fan should know this since all the mobile homes down there have at least 31" mud grips.

B'ham Jeeper · #4 (**permalink**) 09-13-2007, 07:51 PM

Dang I didn't know I was going to have to do math! Ok so my tire is a 255/70/18 and that calculated to 32". Does that sound right? (you know being and Auburn fan and all!)

currupt4130 · #5 (**permalink**) 09-13-2007, 08:29 PM

http://www.4lo.com/calc/gearmetric.htm

redrooster · #6 (**permalink**) 09-14-2007, 11:44 AM

Sounds right. Now go out there and measure the true height with a tape measure. I bet it's under 30" mounted with weight on it.

jfrabat · #7 (**permalink**) 09-14-2007, 12:12 PM

Keep in mind that "advertized" size and "real" size varies... Meanining that you can buy a 32" tire that really measures 31", so dont count on the sidewall to be exact...