What 185/60R15 means
The inputs are 185 mm nominal section width, a 60-percent aspect ratio, and a 15-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 185 × 60 ÷ 100 = 111 mm. Adding two sidewalls to the 381 mm rim gives 603 mm (23.74 in) of nominal outside diameter.
A calculated reference
The 60-percent ratio gives a sidewall of 111 mm. Increasing the ratio to 65 at the same width and rim would add 9.25 mm per sidewall and 18.5 mm to overall diameter. You can explore that example in the editable tool without treating it as an installation recommendation.
Using a perfect-circle model, circumference is 1894.38 mm, equivalent to 527.88 revolutions per kilometer or 849.54 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 185/60R15, article 15576030000. 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