I know how to read 285/70/17 and 33/12.50/17.....But what's the difference and why are tires sold in these two different forms. It's making shopping for tires difficult.

Also I know that a tire in the 35 inch category can measure 34.5 or whatever. Is this the case with the other form of measurement? can a 33/12.50/17 measure only 32.5?

Thanks, and sorry if this is a dumb question.

 

I don't know why they use those kind of measurements. In my theory I would say because once you install supposed "same size" tires on different size rims, the air pressure will alter their supposed "exact" height and width. So the manufactures use these numbers in a ratio.

But, to make tire purchasing easy, I always use this sheet to get the tire size I truly desire...

http://www.bfgoodrichtires.com/specs...t-a-ko/44.html

 

Nice chart but that's just for BFGs......I wanted to go with Toyo open country M/T 34's but they are a $100 more per tire than a cheaper 35in. I'm looking at Cooper discoverer 34in....but i'm still in the 33s, 35s, or 33s dilema like most. But it comes down to moeny and that fact that I don't wheel that hard or often to warrant expensive tires.

 

BFG, Toyo, Goodyear, etc. They all use the same measurement.

So for example, lets say you want a tire that is exactly 33 inches and 11.5 inches wide. Just find the height then width, skim your finger across and see what the measurement is -- that measurement will be the same fore all other manufactures. I promise. The only difference is tread depth, which has nothing to do with height.