Sidewall, overall diameter, and circumference from a 205/55R16-style size.
| Sidewall | – |
| Diameter | – |
| Circumference | – |
Use this to compare two sizes or to feed the RPM-speed tool. Sidewall = section × (aspect ÷ 100). Overall diameter = 2 × sidewall + rim diameter. Circumference = π × overall diameter. A 205/55R16 is about 632 mm overall. Section is typically millimetres; the rim defaults to inches (ISO tire marking). You can switch either length to mm or inches. Speedometer error from a diameter change is not computed here.
Section: Width of the tire.
Aspect (%): Sidewall height as a percent of section.
Rim: Wheel diameter. Defaults to inches.
Sidewall / Diameter / Circumference: Geometry of that size.
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