The tyre code marked on the side contains information on the proper use of the product, its load capacity, size and durability at the high temperatures caused by fast driving. The code is regulated by the rules in the ECE-R 30 standards, applicable in Europe. These rules apply mainly to the marking on the side wall of the product. This tells us about the most important parameters of the tyre. The size of a tyre can be read off from its side.
185 – tyre width. The tyre code begins with information on the width of the tyre, expressed in millimetres. The difference between the tyre width designations is always 10 mm, as with models such as 175/65 R14, 185/65 R14 and 205/55 R16. The true width of a tyre usually differs somewhat from the value stated by the manufacturer. The number 185 means a distance of 185 mm between the most extreme point on the outer side wall and the most extreme point on the inner side wall, when the tyre is properly mounted on a wheel. This is the cross-sectional width of the tyre.
60 is the tyre aspect ratio. The second value in the tyre code is the aspect ratio for the tyre. This information allows us to quickly calculate the percentage ratio of the tyre’s height to its width. In simple terms, this number indicates what percentage of the width of the model is accounted for by the height of the side. In the example code 185/60 R14, the number 60 means 60% of 185 mm. This means that the actual height of the tyre wall is 111 mm. Tyres with low aspect ratios, with values such as 50, 45 and 40, are called low-profile tyres. In the case of higher-profile tyres the aspect ratio information is not included; for example, in the 165R13, the aspect ratio is 80.
The letter R designates tyres with a radial construction. These tyres contain layers of fibres running in a radial direction, across the tyre. A tyre marked 185/60 R14 has body layers running radially from the theoretical centre of the wheel. Radial tyres account for 98% of all tyres purchased by drivers worldwide.
14 indicates the diameter of the wheel rim on which the tyre should be mounted. Manufacturers give this parameter in inches.