Tyre size conversion US / European system

The sizes of some tyres are indicated in inches in accordance with the American measurement system.

It reads : 32 x 11.5 R 15 LT - total height of the tyres x width R diameter :

• 32 : Tyre diameter in inches.
• 11.5 : Tread width in inches.
• R : Radial tyre.
• 15 : Interior tyre diameter or rim diameter in inches.
• LT : U.S. term for "Light Truck".

The conversion into the European metric system is simple enough since :

1 inch = 2,54 cm

For example the US size 32 x 11.5 R 15 corresponds to the following size in Europe :

Sidewall height :

( (heightUS x 2.54 - diameter x 2.54) / 2 ) / (widthUS x 2.54) = height in %

((32 x 2.54 - 15 x 2.54) / 2 ) / (11.5 x 2.54)= 74%

Then, you only have to round it up to the closest existing height : 75

Tyre width :

11.5 x 2.54 = 29.21 cm = 292mm

You then have to round it up to the closest existing width : 295mm

The diameter stays the same.

The US 32 x 11.5 R 15 size corresponds to the European size 295/75 R 15