Tire Size Decoded: What 225/65R17 Actually Means
August 1, 2026 · tires · buying guide · basics
Reading the sidewall
Take 225/65R17 102H. Every piece of that means something specific.
- 225 is the section width in millimeters, measured sidewall to sidewall.
- 65 is the aspect ratio: the sidewall height is 65% of the width. Lower number, shorter sidewall, sportier ride.
- R means radial construction. Nearly everything on the road is radial.
- 17 is the wheel diameter in inches.
- 102 is the load index, which maps to a maximum weight per tire.
- H is the speed rating.
Why you cannot just change one number
People love the idea of a taller tire. The catch is your speedometer, your ABS, and on newer trucks your transmission shift points all assume a specific rolling diameter. Go more than about 3% off stock and your speedometer starts lying to you.
Load index is not optional
On a half-ton truck or anything that tows, dropping below the factory load index is the single most common dangerous mistake we see. A tire that looks identical can be rated for hundreds of pounds less. Match or exceed the factory number, always.
Bring us the number off your door jamb and we will do the math for you.