BMW - Toothed Belt Drive


The innovative rear wheel drive, in which a toothed belt transfers engine power to the rear wheel, ensures clean and maintenance free power transmission. Together with the single sided swing arm of light alloy, it is an entirely new concept in motorcycle design. With this combination, the secondary drive can be regarded as the equivalent of the clean and low maintenance shaft drive. Specially developed for BMW Motorrad, the toothed belt not only runs extremely quietly, but is also extremely durable owing to its aramid fibre reinforcement. After the correct tension has been set during the first service, it is checked every 10,000 km, with a routine replacement at 40,000 km. The toothed belt is tightened over the bearing that guides the rear wheel in the single sided swing arm. The mono swing arm ensures that the rear wheel is always positioned perfectly. The belt is constantly under tension, therefore minimising any load change reactions. This is a major advantage over the conventional chain drive. The load change reactions are further reduced by means of a jerk damper fitted with four elastomer blocks. The durability of the drive system is ensured by the toothed belt wheel in stainless steel and the output pinion gear with a steel inner core. The sprocket consists of a sintered metal alloy. This combination ensures minimum wear. These weight savings compared with the chain drive also help to reduce centrifugal forces and so improve the efficiency of power transmission.