Tire Size Conversion

B-Cack · Dec 9, 2004

OK, just wanted to know if anyone knows off the top of their head what a Goodyear P-265 equates to? 31" or 33" Trying to decide what kind of tires I want to put on my 93, and I have the P-265 now, I think they look a little small......

Bradt · Dec 9, 2004

Need to know the rest of it.

The 265 tells us your tire size is 10.5 inches wide. The next number is the percentage of tread width that equals the sidewall height.

So if it is 265/75 you would have

((10.5 *.75) * 2) + rim diameter = total height.

For me:
((10.5 *.75) * 2) + 15 = 30

brad

EDIT- I guess I should say that the 265 is the tread width in milimeters.

Guest_B-Cack · Dec 9, 2004

Ok thanks, I guess I will get off my ass and go get the numbers........ hang on

Guest_B-Cack · Dec 9, 2004

P265 75 R15.............assume that is the size?

Bradt · Dec 10, 2004

It would be right at 30.75

I don't know if that would be classified as 30 or 31. Mine were supposed to be 31, and they are the same size as yours. Now that I think about it does anyone know if they round up or down for sizes?

Just for reference I'll go through the whole thing.

P265 75 R15

265 mm = roughly 10.5 inches of tread width
75 = percentage of tread width that equals the sidewall height
15 = rim diameter

( the P is for Passenger and the R is for Radial)

sidewall height = tread width * percentage
7.875 = 10.5 * .75

Since there is sidewall on both sides of the rim we double that to get
15.75

Add rim diameter
15.75 + 15 = 30.75

brad

Guest_B-Cack · Dec 10, 2004

Dude,
thanks, I knew that tire wasn't that big. A friend of mine just bought some tires for his Expedition and swears that they are 33's. they are the same damn size as mine and I know it isn't that big... hell.... they look ridiculous on the Expedition...... I have heard that a 33 will fit a stock Bronco... I have a 93 XLT... I am pretty sure it will fit, looks like I might have to remove the air damn though.... Hey, since you are a tire minded guy, could I fit say a BFG AT or MT on that 15 inch wheel or should I invest in something a little bigger?

Justshootme84 · Dec 10, 2004

That's a good explanation of the tire numbers!!! You will find that the same "size" tire like a 33x12.50R15 is not always 33 inches tall. Different brands will not all be that height. Going to a wider rim will also decrease the height a small bit. You can mount 33's to the factory 15x7" rim or a 15x8", but they will have some sidewall bulge. Good for mud but bad for rocks, as the sidewalls are rather thin on most tires.