215/55R17 tyre size
A 215/55R17 tyre is 215 mm (8.5") wide with a sidewall height of 55 % of the width, i.e. 118.3 mm (4.7"), on a 17" (432 mm) rim. Overall diameter is 668.3 mm (26.3"), so the closest inch-style size is 26.3×8.5R17. Static circumference is 2100 mm; the ETRTO rolling circumference is 2038 mm, giving 491 revolutions per km (790 per mile).
Dimensions and rolling diameter
| Section width | 215 mm | 8.46″ |
| Sidewall height | 118.3 mm | 4.66″ |
| Rim diameter | 431.8 mm | 17″ |
| Overall diameter (static, unloaded) | 668.3 mm | 26.31″ |
| Static radius | 334.2 mm | 13.16″ |
| Static circumference (π × D) | 2,100 mm | 82.7″ |
| Rolling circumference (ETRTO 3.05 × D) | 2,038 mm | 80.2″ |
| Effective rolling radius | 324.4 mm | 12.77″ |
| Revs per km (rolling / static) | 491 / 476 | |
| Inch equivalent | 26.3×8.5R17 | |
| Approved rim widths (approx.) | 6″–8″ (measuring rim 7″) | |
A 215/55R17 tyre is 215 mm (8.5") wide with a sidewall height of 55 % of the width, i.e. 118.3 mm (4.7"), on a 17" (432 mm) rim. Overall diameter is 668.3 mm (26.3"), so the closest inch-style size is 26.3×8.5R17. Static circumference is 2100 mm; the ETRTO rolling circumference is 2038 mm, giving 491 revolutions per km (790 per mile).
Why two circumferences? The static figure is simple geometry (π × diameter). Under load a radial tyre flattens and rolls about 3 % less per revolution; ETRTO defines the rolling circumference as 3.05 × the nominal diameter, which is what manufacturers quote and what speedo and gearing calculations should use.
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