It happens out of the blue and is not even audible. Suddenly you step into the void, as if the chain had broken. But it's not the chain, it's the drive belt inside the Brose Drive S-Mag motor - the part that makes the Brose so quiet compared to the competition. Experts are debating the reasons for the defect: some speak of tolerance problems, others blame the power peaks at high torques in the low cadence range for the mishap. The fact is that some motors have lasted for years without any problems, while the defect recurs in others.
Brose has now reacted. The 7.3.6 software update cuts the small power peaks and thus protects the motor from excessive loads. The update can be installed at the dealer, and we have also learnt from company sources that the warranty for S-Mag engines is to be extended. In order to determine the effects of the software update on driving performance, we carried out an extensive before/after check with the Drive S Mag, both in practice and on our laboratory test bench.
Price: free of charge
Info: www.brose.com
Markus Greber, test editor EMTB:
Does the update make the S Mag weaker? To answer this anxious question, we tested two motors - one with and one without the update.
ConclusionThe motors functioned noticeably differently in terms of their characteristics. It is not possible to say whether this is due to the update or to the well-known series variation at Brose. In our comparison, the motor with the update even felt slightly more powerful. However, the update delivered a real surprise on our test bench: the Rotwild RX 750 Ultra only ran out of steam after a whopping 1801 metres of climbing. We tested the comparable setup, but without the update, in EMTB Issue 01/20 in a Rotwild RC 750 Pro: at that time, it only delivered 1587 metres of altitude. The result confirms Rotwild's practical tests, according to which a significantly greater reach height is now available thanks to the update. However - as our test bench also confirms - the motor switches to energy-saving mode much earlier with the update. From an altitude of around 1500 metres, only a significantly reduced amount of power is available.
