2008 Mercedes S-Class Owner's Manual - Page 570

Operation Tires and wheels Tire width The tire width 1 ( page 568) indicates the nominal tire width in mm. Aspect ratio The aspect ratio 2 ( page 568) 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 The tire code 3 ( page 568) 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" ( page 570). Rim diameter The rim diameter 4 ( page 568) is the diameter of the bead seat, not the diameter of the rim edge. Rim diameter is indicated in inches (in). Tire load rating The tire load rating 5 ( page 568) 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 lbs (615 kg) the tire is designed to support. See also "Maximum tire load" ( page 573) where the maximum load associated with the load index is indicated in kilograms and lbs. Warning! G The tire load rating must always be at least half of the GAWR ( page 576) of your vehicle. Otherwise, tire failure may be the result which may cause an accident and/or serious personal injury to you or others. Always replace rims and tires with the same designation, manufacturer and type as shown on the original part. Warning! G Do not overload the tires by exceeding the specified load limit or total load limit as indicated on the Tire and Loading Information placard located on the driver's door B-pillar ( page 553). Overloading the tires can overheat them, possibly causing a blowout. Overloading the tires can also result in handling or steering problems, or brake failure. 569