Tire sidewalls are carrying more information than ever
Decoding the information on tire sidewalls is getting tougher and tougher for the layman. And no wonder: The number of different specifications is steadily increasing, which means tire manufacturers like Continental, who supply original equipment, have to add more indicators to the sidewall. These sequences of numbers, letters and in some cases symbols can help you identify the right tire for your car. By way of example, in what follows, Continental decodes the sequence “225/45 R 18 95 H SSR MOE M+S”.
The number “225” stands for the width of the tire in millimeters – so in this case the tire is 22.5 cm wide. The “45” that follows is the aspect ratio - the height of the tire sidewall as a percentage of its width. In our case that means 10.1 cm. Next up is an “R”, which means “radial” – today, radial tires have almost completely replaced the cross-ply tires that were the standard design until the 1980s. The figure “18” indicates the wheel rim diameter in inches, while “95” is the load index, indicating the maximum weight the tire can bear; 95 equates to 650 kg. Then comes the letter “H” which is the speed index, where “H” signals a maximum speed of 210 km/h. “SSR” indicates that this is a “SelfSupportingRunflat” tire. The abbreviation “MOE” tells us this is a Mercedes original equipment tire with runflat properties (E = extended mobility). The number of these manufacturer-specific codes is set to rise even further in years to come as more and more automakers submit their own specifications to the leading tire manufacturers. The final element “M+S” stands for “mud and snow” – so this is a winter tire or an off-highway model. Anyone looking for a safe winter tire should also look out for the snowflake symbol on the sidewall, because tires with this symbol have proven their grip on snow in a standardized test.
Along with this data, the tire sidewall carries lots of other information, too. One important item for drivers is the production date, indicated by what’s called the DOT code. It’s made up of the letters DOT and two pairs of figures, separated by a forward slash. The first two numbers show the week the tire was built; the last two indicate the year. So “36/16” means the tire was built in the 36th calendar week (i.e. between September 5 and 11) in 2016. Drivers looking for these codes on their tires should inspect both sidewalls, as there are indicators on both sides – which on the vehicle can mean on the inner wall, too.