The drive with chain and derailleur is highly efficient with low frictional losses and can be produced cheaply on an industrial scale. But the system has disadvantages: It is prone to wear and tear, the rear derailleur is exposed and prone to failure and it adds weight to the rear wheel, which is detrimental to optimum suspension performance.

Therefore, it makes sense to think about alternative shifting concepts. The German manufacturer Pinion has taken the most radical, and so far quite successful, approach. Here, the gears are not located on the rear wheel, but centrally, with a low center of gravity in the middle of the bike as a gearbox. Pinion had already thought about the marriage of gearbox and electric motor - and presented a study at Eurobike 2011. Pinion has not yet brought these plans to market maturity.Kervelo from France is also building a Pinion-style gearbox - but the manufacturer is attracting even more attention with the launch of the Quartz integrated e-bike drive. This is based on the planetary gearbox of the gearbox, an electric motor positioned above the gearbox and, of course, a 48V battery. The motor delivers its power to the crankshaft via the planetary gearbox, thus providing plenty of pedal assistance. Speaking of assistance: Quartz delivers a maximum output of 250 W (400 W for the S-Pedelec version) and pumps up the slope with around 70 Nm. The versions available are Quartz 4 (4 gears, 200% range), Quartz 6 (6 gears, 323% range), Quartz 12 and Quartz 12 Speed (12 gears each with 545% range).

With these four systems, the Quartz system aims to meet the needs of urban e-bikers, e-road riders, e-mountain bikers and S-pedelec riders. The weights of the gear/motor unit are moderate and competitive at 3.3 to 3.9 kg.

kervelo.com