Tyre measurements explained

If you see a road tyre with the measurements in the format below:

205 /      55   R    /      16   91 W
A    /      B           /        C      D   E

Then the following process allows you to determine the dimensions of the tyre:



A = Width of tyre (in millimetres)
In this example it shows that the tyre is 185mm wide.

B = Tyre profile as a percentage of width (A).
In this example the ratio is 60% of 185mm. This works out as 111mm.

C = Diameter of inner rim (in inches).
In this example it shows that the rim is 15″ in diameter.

D = the load rating, e.g the maximum load that can be placed on the tyre.

E = Tyre speed rating.


Read the full article, including information on Loads per tyre, tyre speed rating, and cycle tyre measurements

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