Actual size vs printed

My 00 XLT came stock with Good year Wranglers 255/70 R16 Wich work out to be just over 30" tall. I was just about to hit buy on Cooper 265/75 R16 which work out to be 31.6" tall when I decided to measure the tires on the truck. I got 28.5(being generous) what am i missing? I run the tires at 30psi and they are easly legal but warn. i find it hard to belive i've lost 3/4" of tread (top & bottem for 1.5") when thease tires don't have the deepst tread to begin with.

by Contrast i measured relatively new tires on a truck at work that are 265/70 R17 wich work out to be about the size of the coopers i'm looking at (31.6) and got 31.5...spot on.

I take it the printed measuments include tread? What other factors effect the size?

I want to get the biggest tires i can with my 2" lift (TT & shackles). According to the sticky thread thats about 32". 31.6 is as close as i can find in the tire i want.

 

[Anime]

When you roughly measure a tire that is worn, inflated, and mounted on a wheel, you're not even close to measuring what the manufacturing measurements are. When a tire manufacturer shows a chart of tire sizes, and lists things like the diameter, tread width, section width, weight, etc., those are the manufactured-to specs. If you used a gigantic caliper, (or a long measuring tape and some math), you can get the diameter of a brand new, unmounted tire, and it'd be pretty close to the spec.

Measuring this tire of one size on one vehicle and that tire of another size on another means very little. Everything from the width of the wheel the tire is mounted on, to the weight of the vehicle and cargo pushing down on it, completely changes the measurements of a tire. If you look at the tire manufacturer's measurement charts, you'll notice they list those measurements as being valid for a particular wheel width. Mounting the tire on a wider or narrower wheel will change those measurements. Inflating it more or less changes it more. Putting weight on it (especially a radial tire) distorts it to the point it's no longer even a circle.

You're best off using the information in the charts as a way to compare one tire to another. Using what you've already got, going with 265/75R16 is good if you want the biggest tire that will fit on there for whatever reason.

If you go with the LT265/75R16 Coopers, I'd suggest going for the ones that are Load Range C. They make that size in a Load Range C and a Load Range E. Load Range E is for heavy duty fullsize trucks that tow lots of weight, so that tire will be too firm and also extremely heavy, with no real benefit on an Explorer.

 

[Cstoliker]

Going by what I've already got, I could go much bigger. The tires on the truck look small in the fenders. If I'll loose 1.5" on the new tires (wich will be the same load range) I could go with 33"s and expect them to actually be 31.5?

My rims are 16x7.

 

[Anime]

The tires aren't actually 1.5" smaller. What you're measuring as being 28.5 isn't the actual diameter of the tire, it's a guess based on a visual reading of a tape measure.

To even come close to getting the diameter, you'd need to remove the tire/wheel, lay it flat, measure the circumference, and do the math to get the diameter. Then you'd have an idea of what the diameter of the worn, inflated tire is on a 7 inch rim.

Also, 32 inch tires are not exactly 32 inches in diameter. Most 32's are 31.6, 31.5, or even smaller.

This is the same for almost any tire size. 31's are really 30.5 inches. 33's are really 32.5 inches. It's not an absolute measurement and varies by manufacturer.


The largest tire that will fit for what you're interested in is 265/75R16, which is 31.5-31.6 inches in diameter.

 

[Cstoliker]

Thanks!