2007 BMW 7 Series Owner's Manual - Page 206

Wheels and tires Temperature The temperature grades are A, B, and C, A being highest, and represent the tire's resistance to the generation of heat and its ability to dissipate heat when tested under controlled conditions on a specified indoor laboratory test wheel. Sustained high temperature can cause the material of the tire to degenerate and reduce tire life, and excessive temperature can lead to sudden tire failure. The grade C corresponds to a level of performance which all passenger car tires must meet under the Federal Motor Vehicle Safety Standard No. 109. Grades B and A represent higher levels of performance on the laboratory test wheel than the minimum required by law. The temperature grade for this tire is established for a tire that is properly inflated and not overloaded. Excessive speed, underinflation, or excessive loading, either separately or in combination, can cause heat buildup and possible tire failure.< Minimum tread depth The tread depth should not fall below 0.12 in/ 3 mm, although, for example, European legislation only specifies a minimum tread depth of 0.063 in/1.6 mm. At tread depths below 0.12 in/3 mm, there is an increased risk of high-speed hydroplaning, even when only small amounts of water are present on the road surface. Winter tires display a noticeable loss in their ability to cope with cold-weather driving conditions once the tread wears to below 0.16 in/ 4 mm. To ensure continued safety, you should always have such tires replaced. RSC Run-flat tires You will recognize run-flat tires by a circular symbol containing the letters RSC on the side of the tire, refer to page 205. M+S Winter and all-season tires. These have better winter properties than summer tires. Wear indicators at the tread-groove base, refer to arrow, are distributed over the tire's circumference and are marked on the side of the tire with TWI - Tread Wear Indicator. If the tire tread has been driven down to the wear indicators, a tread depth of 0.063 in/1.6 mm has been reached. Wheel/tire damage Please note that low profile tires make wheels, tires, and suspension parts more susceptible to road hazards and consequential damages. Unusual vibrations encountered during normal vehicle operation can indicate tire failure or some other vehicle defect. This can, for example, be caused by driving over curbs. These kinds of problems may also be signaled by other changes in vehicle response, such as a strong tendency to pull to the left or right. In these cases, reduce speed immediately and have wheels and tires thoroughly checked. Drive carefully to the nearest BMW center or tire shop that works according to BMW repair procedures with correspond- XL Indicates specially reinforced tires. Tire condition Inspect your tires frequently for tread depth, signs of damage and for foreign objects lodged in the tread. Check the tread depth. 204 Online Edition for Part no. 01 41 0 013 316 - © 02/07 BMW AG