2010 Mercedes C-Class Owner's Manual - Page 249

Tires and wheels Letter "T" preceding the size designation: Temporary spare tires which are high pressure compact spares designed for temporary emergency use only. Tire width Tire width : indicates the nominal tire width in millimeters. Aspect ratio Aspect ratio ; is the dimensional relationship between tire section height and section width and is expressed in percentage. The aspect ratio is arrived at by dividing section height by section width. Tire code Tire code = indicates the tire construction type. The "R" stands for radial tire type. Letter "D" means diagonal or bias ply construction; letter "B" means belted-bias ply construction. At the tire manufacturer's option, any tire with a speed capability above 149 mph (240 km/h) can include a "ZR" in the size designation (for example: 245/40 ZR 18). For additional information, see "Tire speed rating" (Y page 247). Rim diameter Rim diameter ? is the diameter of the bead seat, not the diameter of the rim edge. The rim diameter is indicated in inches (in). Load index and Loading Information placard on the driver's door B-pillar. Overloading the tires can overheat them, possibly causing a blowout. Overloading the tires can also result in handling or steering problems, or brake failure. 247 Load index A is a numerical code associated with the maximum load a tire can support. For example, a load rating of 91 corresponds to a maximum load of 1356 lb (615 kg) the tire is designed to support. See also "Maximum tire load" (Y page 242) where the maximum load associated with the load index is indicated in kilograms and lbs. For additional information on the load index, see "Load identification" (Y page 249). Speed symbol G Warning! Even when permitted by law, never operate a vehicle at speeds greater than the maximum speed rating of the tires. Exceeding the maximum speed for which tires are rated can lead to sudden tire failure, causing loss of vehicle control and possibly resulting in an accident and/or serious personal injury and possible death, for you and for others. G Warning! The tire load rating must always be at least half of the GAWR of your vehicle. Otherwise, tire failure may be the result which may cause an accident and/or serious injury to you or others. Always replace rims and tires with the same designation, manufacturer and type as shown on the original part. Regardless of the tire speed rating, local speed limits should be obeyed. Use prudent driving speeds appropriate to prevailing conditions. Speed symbol B indicates the approved maximum speed (tire speed rating) for the tire. Summer tires Index Q R S T Speed rating up to 100 mph (160 km/h) up to 106 mph (170 km/h) up to 112 mph (180 km/h) up to 118 mph (190 km/h) Z G Warning! Do not overload the tires by exceeding the specified load limit as indicated on the Tire Operation