Drivers Technology.

 

Tyre Size Coding explained

A tyre is referenced as "185/60R/15H", here is an explanation.
A/B/C
A = Width of Tyre (mm)
In this example it shows that the tyre is 185mm wide.
B = Profile as a % of width.
(i.e. profile is 60% of width)
In this example the ratio is 60%. This works out as 111mm.

C = Diameter of inner rim.
In this example it shows that the rim is 15" in diameter.

From this you can also work out your rolling circumference.

e.g. (2 x B) + C = diameter = d

therefore (2 x 111 = 222) + (15" x 25.4 = 381) = 603mm

circumference = pi x d = 3.142 x 603 = 1895mm