The Brose motor has been around for a while now, and we’ve tested a number of bikes using the system. The belt drive internals make for very quiet progress, and the motor has plenty of power on tap too.

Now Brose has a new version, called the S-Mag. The Mag stands for Magnesium: the whole of the outer shell has been replaced with a cast magnesium alloy unit that saves 400g. In total the weight of the motor has been reduced by half a kilo, from 3.4kg to 2.9kg.

Internally, the physical mechanism is the same: Brose is still using the same motor and a belt drive for quiet operation; it's always been one of the quieter motors out there. The performance of the motor has been improved, but that’s down to new electronics and control firmware.

There’s a new mode – flex power – that is designed for mountain biking and offers 30% more power than before when you’re attacking hills in a high cadence. The use of cadence in the power algorithm is new for Brose, which up until now has relied on torque sensing to apply the assistance

Brose is offering the motor with two mounts, the existing side mount that’s currently used, and a vertical mount that should make it easier for manufacturers to implement the motor. Brose is also developing its own series of displays for use with the motor.

We haven’t had a chance to try out the S-Mag motor yet but we’d expect the ride experience to be similar to the previous Brose motors, and that’s no bad thing. The higher performance and lower weight will certainly appeal to riders looking for top-end performance, so expect to see it on high-ticket city bikes and e-MTBs.