205/55R16 tyre size
A 205/55R16 tyre is 205 mm (8.1") wide with a sidewall height of 55 % of the width, i.e. 112.8 mm (4.4"), on a 16" (406 mm) rim. Overall diameter is 631.9 mm (24.9"), so the closest inch-style size is 24.9×8.1R16. Static circumference is 1985 mm; the ETRTO rolling circumference is 1927 mm, giving 519 revolutions per km (835 per mile).
Dimensions and rolling diameter
| Section width | 205 mm | 8.07″ |
| Sidewall height | 112.8 mm | 4.44″ |
| Rim diameter | 406.4 mm | 16″ |
| Overall diameter (static, unloaded) | 631.9 mm | 24.88″ |
| Static radius | 316.0 mm | 12.44″ |
| Static circumference (π × D) | 1,985 mm | 78.2″ |
| Rolling circumference (ETRTO 3.05 × D) | 1,927 mm | 75.9″ |
| Effective rolling radius | 306.7 mm | 12.08″ |
| Revs per km (rolling / static) | 519 / 504 | |
| Inch equivalent | 24.9×8.1R16 | |
| Approved rim widths (approx.) | 5.5″–7.5″ (measuring rim 6.5″) | |
A 205/55R16 tyre is 205 mm (8.1") wide with a sidewall height of 55 % of the width, i.e. 112.8 mm (4.4"), on a 16" (406 mm) rim. Overall diameter is 631.9 mm (24.9"), so the closest inch-style size is 24.9×8.1R16. Static circumference is 1985 mm; the ETRTO rolling circumference is 1927 mm, giving 519 revolutions per km (835 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.
Buying tyres for your business?
Onyx Tyres supplies workshops, retailers and fleets across Australia at wholesale prices. Open a trade account to see stock and pricing and order online.