De-coding Tires

[Randalla]

I always have to go to the internet to determine what all the numbers mean on the sidewall of tires, so I put together this cheat sheet and thought some of you might also find it helpful:

Tire Width (mm)- this number is usually the first one in the size description, 255/ 40/17

Sidewall Height (% of tread width)- this number is the second one in the size description 255/40/17

Wheel Size (inches)- this number is the last one in the size description 255/40/17

Date of Manufacture- the DOT Code shows the week and year of manufacture. A DOT code of 1015 means the tire was manufactured the 10th week of 2015.

Speed Ratings- single letter ratings on the tire indicate maximum speed rating. S- up to 112 mph, H- up to 130 mph, V- up to 149 mph, Z- up to 149 mph, W- up to 168 mph, V- up to 186 mph.

Temperature Grade- grades range from A to C, with A being the highest rating and C being the lowest.

Traction Grade- grades range from AA to C, with AA being the best wet traction and C being the worst

Tread Wear Grade- grades range from 100 to 600, with the higher number designating longer tread wear and harder compound, and the lower number designating shorter tread wear and softer compound. Note: tread wear numbers are only comparable within brands, not between brands.

[Turboman280]

Great info, Thanks Randy!

[L320-Dale]

Good information Randy! I'll just correct one detail if I may....

In your example 255/40R17..... The 40 is not mm, its the "Aspect ratio" meaning the sidewall height is 40% of the section width (255mm). In this example the aspect ratio would be 102mm.

So to find the approx overall height of this tire in inches would be.

255 (section width) X 40 (aspect ratio) X 2, divided by 2540 (converts metric to inches) + 17 (rim diameter) = 25.03 inches tall.

[Randalla]

You're right Dale. Thanks for the correction. I'm editing my post to reflect that change.