What 225/55R17 means
The inputs are 225 mm nominal section width, a 55-percent aspect ratio, and a 17-inch nominal rim diameter. The R identifies radial construction. The width is not a wheel-width measurement, and the rim number is not the outside diameter of the tire.
Nominal sidewall height is 225 × 55 ÷ 100 = 123.75 mm. Adding two sidewalls to the 431.8 mm rim gives 679.3 mm (26.74 in) of nominal outside diameter.
A calculated reference
A 55-percent ratio gives 123.75 mm per sidewall. In the 215/55R17 comparison, the 10 mm increase in width becomes 11 mm of total-diameter change. The rim contribution stays at 431.8 mm for both entries.
Using a perfect-circle model, circumference is 2134.08 mm, equivalent to 468.59 revolutions per kilometer or 754.11 per mile. These are derived from unrounded diameter; actual rolling circumference also depends on the product and operating conditions.
Source and scope
General Tire’s AltiMAX RT45 source includes 225/55R17, article 15576400000. It was checked on October 27, 2026. That record verifies the published marking used here; it does not turn these calculated dimensions into that product’s measured specification or establish availability.
Use the exact product and vehicle requirements for load and speed ratings, permitted rim dimensions, inflation and clearance. Nominal geometry alone cannot verify fitment, braking behavior, handling or safety.
Sources and further reading
- AltiMAX RT45 — General Tire
- Tire Markings Explained — Michelin
- Tire glossary — Michelin