What 205/55R16 means
The inputs are 205 mm nominal section width, a 55-percent aspect ratio, and a 16-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 205 × 55 ÷ 100 = 112.75 mm. Adding two sidewalls to the 406.4 mm rim gives 631.9 mm (24.88 in) of nominal outside diameter.
A calculated reference
The 112.75 mm sidewall is calculated before rounding. Rounding it to 113 mm before doubling would inflate the final diameter by 0.5 mm. TireSpan retains the original precision for circumference, percentage and speed-ratio calculations.
Using a perfect-circle model, circumference is 1985.17 mm, equivalent to 503.73 revolutions per kilometer or 810.68 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 205/55R16, article 15576160000. 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