How to read a tire sidewall
Take 225/45R17 94V XL as the example.
Size
- 225: section width in millimeters.
- 45: aspect ratio, the sidewall height as a percentage of width. Lower numbers mean a shorter sidewall, sharper handling and a harsher ride.
- R: radial construction. Effectively all modern tires.
- 17: rim diameter in inches.
A P before the size (P225/45R17) marks a passenger tire; LT marks a light-truck tire with a stiffer, heavier construction and different pressure requirements. Don't mix the two on one car.
Load index and speed rating
- 94: load index. Each number maps to a maximum weight per tire; 94 is 1,477 lb. Never go below the index on the door-jamb sticker.
- V: speed rating. S is 112 mph, T 118, H 130, V 149, W 168, Y 186, with Z used for anything over 149. The rating also reflects construction and heat tolerance, which is why we give it a small weight in the score.
- XL or Extra Load: reinforced for higher pressure and load. Required on many EVs and heavier crossovers.
DOT code
The string beginning DOT identifies the plant and the week of manufacture. The last four digits are the week and year: 2326 is the 23rd week of 2026. Tires harden with age; six years is a common replacement threshold regardless of tread.
UTQG grades
Treadwear, traction and temperature, like 640 A A. See UTQG explained.
Winter markings
M+S means the tread shape qualifies as mud-and-snow; no test is involved. The three-peak mountain snowflake means the tire passed a severe-snow traction test. See 3PMSF vs M+S.
Other markings you'll see
- Max press. / max load: the tire's limits, not the pressure to use. The correct pressure is on the door jamb.
- Rotation arrow or "Outside": directional or asymmetric tread; mount accordingly.
- Run-flat: often marked RFT, ROF, ZP, SSR or DSST depending on the maker.
- Tread-wear indicators: raised bars across the grooves at 2/32 inch, the legal minimum. Most wet-grip loss happens before that; many testers suggest replacing at 4/32.