How to Read a Tire Sidewall
Decode width, aspect ratio, construction, rim size and service description in seconds.
The size code
In 225/60R17, 225 is section width in millimeters, 60 is the aspect ratio (sidewall height as a percent of width), R means radial construction, and 17 is the rim diameter in inches.
Prefixes
P marks P-metric passenger tires. LT marks light truck tires built for heavier loads and higher inflation. ST is special trailer and must not go on a passenger vehicle. No prefix usually means Euro-metric.
Service description
After the size you'll see something like 99H. The number is the load index, the letter is the speed rating. Match or exceed the OE service description when replacing.
Other markings
Look for the DOT code, maximum load and inflation, UTQG ratings on passenger tires, and the three-peak mountain snowflake symbol on severe-snow-rated tires.