How to Read a Tire Size (P, LT, ST and Commercial Sizes Explained)
June 22, 2026
Decode any tire sidewall — width, aspect ratio, construction, rim size, load index and speed rating.
The basic format
In 225/65R17, 225 is the width in millimeters, 65 is the sidewall height as a percentage of width, R means radial and 17 is the rim diameter in inches.
LT and ST tires
LT means light truck — a stronger tire for heavy loads. ST means special trailer and should only be used on trailers.
Load and speed
The numbers and letter after the size, like 102H, are the load index and speed rating.
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