confused

I'm a little confused on tire sizes. I thought that 265's were the same as 31's, but i was reading the latest Peterson's and they test out the nitto dune grappler on the tahoes 20 inch rims. They tested size 285 and said they were 31 inch tires. Are 285 really 31s?

http://www.redrock4x4.com/tech/tire...m=16&submitButtonName=Calculate&method=metric
Metric Tire Conversion Calculator - Red Rock 4x4

it all has to do with the rim size and the size of the sidewall versus the width of the tire. i cant explain it very well but somebody else will have the correct info

CROSBIKE said:

it all has to do with the rim size and the size of the sidewall versus the width of the tire. i cant explain it very well but somebody else will have the correct info

Click to expand...

The 1st number is width, the 2nd is sidewall height as a percentage of said width, and the 3rd is rim size.

So, a 235/85R16 would be 235mm wide (about 9"), the sidewall height would be 85% of 9" (7.65 x2 b/c of two sidewalls - above and below the rim) plus rim height - 16". The total tire height would be almost 32"; about 31.6 or 7ish IIRC.

Hope that helps...

Starscream918 said:

The 1st number is width, the 2nd is sidewall height as a percentage of said width, and the 3rd is rim size.

So, a 235/85R16 would be 235mm wide (about 9"), the sidewall height would be 85% of 9" (7.65 x2 b/c of two sidewalls - above and below the rim) plus rim height - 16". The total tire height would be almost 32"; about 31.6 or 7ish IIRC.

Hope that helps...

Click to expand...

That is exactly right, the only thing I could add is the fact that even though the tire may state 235/85/16 (which I’m running) true tire size will vary from manufacture to manufacture. Then there is the fact of the manufactures claim of actual dimensions may vary from the true dimensions of the tire. Bridgestone states that my 235/85/16’s have a 30” diameter yet measure 31.5-6.

so should i go with 265/75/r15 or 31x10.5 r15? and is there any way i could go wider with the proper backspacing

kumes12688 said:

so should i go with 265/75/r15 or 31x10.5 r15? and is there any way i could go wider with the proper backspacing

Click to expand...

It doesn't really matter which one you go with. A 31" tire on a 15" rim will be about 30.something inches inflated on the rim; a 265 on a 16" rim will be about the same. Just figure out which rims/what size rims you want and then decide. Me personally - I'd go with a 16" rim and then choose tires from there. 16" rims offer inched sizes and also metrics. 15" rims only go up to about 265s metrically-speaking and that's it. Also note that 16" rims will almost always cost more.