225/50R17 tyre size
A 225/50R17 tyre is 225 mm (8.9") wide with a sidewall height of 50 % of the width, i.e. 112.5 mm (4.4"), on a 17" (432 mm) rim. Overall diameter is 656.8 mm (25.9"), so the closest inch-style size is 25.9×8.9R17. Static circumference is 2063 mm; the ETRTO rolling circumference is 2003 mm, giving 499 revolutions per km (803 per mile).
Dimensions and rolling diameter
| Section width | 225 mm | 8.86″ |
| Sidewall height | 112.5 mm | 4.43″ |
| Rim diameter | 431.8 mm | 17″ |
| Overall diameter (static, unloaded) | 656.8 mm | 25.86″ |
| Static radius | 328.4 mm | 12.93″ |
| Static circumference (π × D) | 2,063 mm | 81.2″ |
| Rolling circumference (ETRTO 3.05 × D) | 2,003 mm | 78.9″ |
| Effective rolling radius | 318.8 mm | 12.55″ |
| Revs per km (rolling / static) | 499 / 485 | |
| Inch equivalent | 25.9×8.9R17 | |
| Approved rim widths (approx.) | 6″–8″ (measuring rim 7″) | |
A 225/50R17 tyre is 225 mm (8.9") wide with a sidewall height of 50 % of the width, i.e. 112.5 mm (4.4"), on a 17" (432 mm) rim. Overall diameter is 656.8 mm (25.9"), so the closest inch-style size is 25.9×8.9R17. Static circumference is 2063 mm; the ETRTO rolling circumference is 2003 mm, giving 499 revolutions per km (803 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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