What 245/45R19 means
The inputs are 245 mm nominal section width, a 45-percent aspect ratio, and a 19-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 245 × 45 ÷ 100 = 110.25 mm. Adding two sidewalls to the 482.6 mm rim gives 703.1 mm (27.68 in) of nominal outside diameter.
A calculated reference
The curated comparison with 255/40R19 is useful because the second tire is nominally wider but smaller in diameter. A lower aspect ratio can outweigh a width increase even when the rim size stays the same.
Using a perfect-circle model, circumference is 2208.85 mm, equivalent to 452.72 revolutions per kilometer or 728.59 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 245/45R19, article 15577590000. 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