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A coded string on a sidewall giving width, profile, construction and rim size.
Also known as: Tyre code, Sidewall marking, Tire size
The main string on a tyre sidewall — something like 205/55 R16 91V — is four separate facts run together. The first number is the section width in millimetres. The second is the aspect ratio, giving the sidewall height as a percentage of that width, so the same profile number means a different height on a wider tyre. The letter marks the construction, R for radial. The next number is the rim diameter in inches, which is why a metric string ends in an imperial figure.
Gives four facts in one string: section width in millimetres, aspect ratio as a percentage of that width, construction type, and rim diameter in inches.
Contexts: Road signage, Vehicle dashboard
Mixes metric and imperial deliberately, because rims have always been sized in inches and tyre sections were metricated later — which is why a size that starts in millimetres ends in inches.
Contexts: Road signage, Vehicle dashboard
Makes the aspect ratio relative rather than absolute, so a 55 profile on a 205 tyre and a 55 profile on a 225 tyre are different sidewall heights — the commonest misunderstanding when a driver changes wheel size.
Contexts: Road signage, Vehicle dashboard
A row of raised numerals and capital letters moulded into a curved rubber surface, separated by a stroke and a space.
Both are read from the same string on the sidewall.