255/55R19 tyre size
A 255/55R19 tyre is 255 mm (10.0") wide with a sidewall height of 55 % of the width, i.e. 140.3 mm (5.5"), on a 19" (483 mm) rim. Overall diameter is 763.1 mm (30.0"), so the closest inch-style size is 30x10R19. Static circumference is 2397 mm; the ETRTO rolling circumference is 2327 mm, giving 430 revolutions per km (691 per mile).
Dimensions and rolling diameter
| Section width | 255 mm | 10.04″ |
| Sidewall height | 140.3 mm | 5.52″ |
| Rim diameter | 482.6 mm | 19″ |
| Overall diameter (static, unloaded) | 763.1 mm | 30.04″ |
| Static radius | 381.5 mm | 15.02″ |
| Static circumference (π × D) | 2,397 mm | 94.4″ |
| Rolling circumference (ETRTO 3.05 × D) | 2,327 mm | 91.6″ |
| Effective rolling radius | 370.4 mm | 14.58″ |
| Revs per km (rolling / static) | 430 / 417 | |
| Inch equivalent | 30x10R19 | |
| Approved rim widths (approx.) | 7″–9″ (measuring rim 8″) | |
A 255/55R19 tyre is 255 mm (10.0") wide with a sidewall height of 55 % of the width, i.e. 140.3 mm (5.5"), on a 19" (483 mm) rim. Overall diameter is 763.1 mm (30.0"), so the closest inch-style size is 30x10R19. Static circumference is 2397 mm; the ETRTO rolling circumference is 2327 mm, giving 430 revolutions per km (691 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.