European tyre markings meet the ERE-R 30 standards. These standards specify markings at the tyre sidewall, where are the most important informations, like tyre size.
175 - width. Tyre width is given in millimeters. It is shown as the first value. Tyre width is changing by 10 mm. for example: 175/65 R14, 185/65 R14The actual width of the tyres usually is a little bit different, than it is shown. Differences depend on manufacturer. Marking 175 means the width of the tyre section, measured on the tyre fitted to a rim between the outermost point of the inner sidewall and the outermost point of the outer sidewall.
65 - tyre profile. Tyre profile is shown as the second value. Indicates the ratio of the hight to the width. It is measured in percent. For example for the size 175/65 R 14 tyre hight is 65% from the width 175 mm. In this case the real profile is 113,75 mm. Tyres with the low profile have markings: 45, 40, 50. Full-profile tyres usually don't have the profile value in their size.
R - means radial construction. Tyres with the radial construction are the most popular tyre models. Radial tyres represent 98% of total sales. In this design, the cord plies are arranged at 90 degrees to the direction of travel, or radially (from the centre of the tire). In the model 175/70 R14 carcass spreads radially from the center of the wheel.
14 - the value which informs about wheel diameter. It is measured in inches.