Car tyres can be placed into three categories: summer tyres, winter tyres and year-round tyres. Winter tyres have a more rough-textured profile than summer tyres and are made of a softer rubber compound. In braking tests, they show a shorter braking distance than summer tyres in outdoor temperatures lower than 7° C. Summer tyres are made of a harder rubber compound and are suitable for use in higher outdoor temperatures.
Here is an example of a tyre marking 185/65 R 15 85 H:
185 is the width of the tyre tread in millimetres.
65 is the percentage ratio of the tyre's width to its cross-section.
R gives information on the design, R means radial.
15 is the diameter of the rims in inches.
85 is the load-bearing index, in this instance 515 kg.
H is the speed index and indicates maximum permitted speeds. In this instance, it is 210 km/h (Q = 160 km/h, T = 190 km/h, H = 210 km/h, V = 240 km/h, W = 270 km/h).