What do the numbers on your tyre's sidewall mean?

When you look at a tyre, you'll see it's got a whole load of numbers and letters printed on the side. You might think that random, or you might understand a few of them, but what do all those numbers and letters really mean?

Taking the tyres on my RS250 as an example, I'll explain what the numbers stand for.

On the rear tyre, it reads: Bridgestone Battlax BT090R Radial 150/60R17M/C 66H

Bridgestone is the manufacturer

Battlax BT090 is the commercial name of the tyre

R stands for radial. This means that the core of the tyre is constructed using a belt made up of several steel plies. This makes for a more rigid tyre construction.

150 is the specified width of the tyre in millimetres

60 is the tyre's height aspect ratio. This means that the height of the tyre is 60% of its width, i.e. 150 x 0.6 = 90. So the tyre is 90mm high.

17M/C designates that the tyre�s inner rim diameter is 17 inches and so is designed to fit a 17 inch motorcycle rim.

66 marks the load index. This means this tyre can carry a maximum load of 300kg when inflated to the correct pressure.

Typical Load Index Chart

58 236kg

62 265kg

66 300kg

70 335kg

74 375kg

76 400kg

80 450kg

84 500kg

H marks the speed index (SI). These tyres are rated to a maximum continuous speed of 130mph (210kph). Although the tyre is capable of achieving higher speeds, it cannot do so under its full load potential.

SI Chart:

J up to 62mph (100kph)

N up to 87mph (140kph)

P up to 93mph (150kph)

S up to 112mph (180kph)

H up to 130mph (210kph)

V up to 149mph (240kph)

W up to 168mph (270kph)

Z over 149mph (240kph)