Tire size confusion

So…Michelin is one of the only, if not the only, manufacturer to use a 275/80-22.5 tire designation. Literally everyone else calls it a 295/75-22.5. If you buy literally any other brand of “lo pro” 22.5, other than Michelin, it will have the latter size designation.
The first number in that designation is the tire carcass width in millimeters, the second number is the sidewall height aspect ratio expressed as a percentage of the carcass width, (in this case 75 or 80% of the width), and the last numbers are the rim diameter.
So….if you do the math, a 275/80-22.5 has an unladen overall height of 39.82” with a 10.82” carcass width, and an 8.66” sidewall height.
A 295/80-22.5 is 39.92” overall unladen height, 11.61” carcass width, and an 8.71” sidewall.
That means (theoretically) that there is less than 1/8” height difference between the two sizes.

 

My comparison was for 295/80/22.5 vs. 295/75/22.5. I missed that the OP has 275/80/22.5’s. That’s good. The speedo and tach will be accurate.

 

Also two tires with the same sidewall numbers can have different RPM (rotation per mile) Cooper and Michelin tire for example 11r 22.5 H load 497rpm vs 503rpm.

 

I wonder what Big Maude's "aspect" ratio is? Hmmm...

 

The 275 & 295 is the width sidewall to sidewall in millimeters. Not tread width because that can vary between makes and models of tires. The 75 & 80 are the aspect ratio of sidewall height to the width in %.

 

Thats a lot to do with tread pattern and types. Tread depth varies between type and maker. Most steers start at 19/32 to 21/32’s range. Most drives or 28 to 32. Keep in mind 32/32 is 1 inch deep.

 

Both examples I listed are steer tires H load. The Michelin is 19/32, the Cooper is 18/32. 1.2% difference in rotation per mile or 1200 miles in a 100k year.

 

Correct. Also another thing is there is an allowable tolerance scale within an inch the manufacturers use. Like an 11-24.5 for example. Some makers build them on the low side so 11 is actually 10.25 inch. While Michelin and Bridgestone build them on the high side so they can actually be 11 or very very close. Cooper is owned by Goodyear since 2019 so they will very close coming from the same plants. Gdy usually built mid range on the scale.