295/40R20 tyre size
A 295/40R20 tyre is 295 mm (11.6") wide with a sidewall height of 40 % of the width, i.e. 118.0 mm (4.6"), on a 20" (508 mm) rim. Overall diameter is 744.0 mm (29.3"), so the closest inch-style size is 29.3×11.6R20. Static circumference is 2337 mm; the ETRTO rolling circumference is 2269 mm, giving 441 revolutions per km (709 per mile).
Dimensions and rolling diameter
| Section width | 295 mm | 11.61″ |
| Sidewall height | 118.0 mm | 4.65″ |
| Rim diameter | 508.0 mm | 20″ |
| Overall diameter (static, unloaded) | 744.0 mm | 29.29″ |
| Static radius | 372.0 mm | 14.65″ |
| Static circumference (π × D) | 2,337 mm | 92.0″ |
| Rolling circumference (ETRTO 3.05 × D) | 2,269 mm | 89.3″ |
| Effective rolling radius | 361.2 mm | 14.22″ |
| Revs per km (rolling / static) | 441 / 428 | |
| Inch equivalent | 29.3×11.6R20 | |
| Approved rim widths (approx.) | 10″–11.5″ (measuring rim 10.5″) | |
A 295/40R20 tyre is 295 mm (11.6") wide with a sidewall height of 40 % of the width, i.e. 118.0 mm (4.6"), on a 20" (508 mm) rim. Overall diameter is 744.0 mm (29.3"), so the closest inch-style size is 29.3×11.6R20. Static circumference is 2337 mm; the ETRTO rolling circumference is 2269 mm, giving 441 revolutions per km (709 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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