On the side wall of the tyre is the tyre code, which tells the driver about the intended use of the tyre, its size, load capacity and durability during travel at high speed, which strongly heats up the rubber.
Since the tyre code contains information about the tyre’s most important parameters, it is subject in Europe to the rules contained in the ECE-R 30 standards.
Each tyre has its code given on its side wall.
The 205/55 R16 tyre has a width of 205 millimetres, because that value is given first in the side marking, expressed in millimetres. The width of the tyre cross-section is the distance between its extreme inner and outer points when mounted on a wheel appropriate for its size. Tyre codes change when the difference in their widths reaches 10 mm. The actual width of a tyre often differs by several millimetres from the value marked on the side, as this depends on the specifics of the given manufacturer.
The tyre aspect ratio appears second in the tyre code marked on the side. For the 205/55 R16 tyre the aspect ratio is 55, which means 55% of the width of 205 millimetres, as this value is the percentage ratio of the height of the profile (side) to the width of the tyre. In this particular case, the profile height is 112.75 mm. Low-profile tyre with values such as 40, 45 and 55 are available, as well as higher-profile tyres, which often do not have the aspect ratio indicated; for example, the 165R13 tyre has an aspect ratio of 80.
Tyres with a radial construction contain layers of fibres running in a radial direction, across the tyre, at a right angle. In the tyre code, radial tyres are denoted with the letter R. In the 205/55 R16 tyre the body runs radially from the centre of the wheel. Radial tyres account for 98% of tyres sold.
16, the final value in the tyre code, shows the diameter of the wheel rim on which the tyre should be mounted. Manufacturers indicate this in inches, as is indicated in the common names for tyres.