Brose’s new eMTB motor is smaller, lighter and even more compact than any of the models previously released by the German manufacturer. Yet it was developed to be even stronger than the current in-house alternatives. We tested the brand new Brose Drive S Mag on different bikes and can tell you what it’s really capable of.

With a compact magnesium housing and a system weight of 2.9 kg Brose’s new Drive S is a true featherweight. This version is not intended to replace Brose’s popular Drive S model but offers a high-end alternative for top-end eMTBs. It churns out 90 Nm of torque and virtually quadruples your leg power with up to 410% of support. Most importantly the magnesium housing is significantly more compact and lighter than the aluminium counterpart you find on the Drive S. All of the above, combined with a number of new sensors and slimmer circuit boards allows the new motor to unleash the additional power without the risk of internal overheating.

Like all Brose motors the Drive S Mag is an open system. This means bike manufacturers can freely choose the components according to their needs — everything from remote controls to batteries, except for the actual motor. Apart from that, a number of housing designs allows them to choose from different mounting options and build lighter, more efficient frames. These features, combined with the reduced size of the motor could help improve the geometry and handling of future eMTBs.

But enough with the theory. How did the Brose Drive S Mag perform on the trail? After riding for just a few metres and spending a couple of minutes familiarising with the Drive S Mag, you’ll forget you’re actually sitting on an electric mountain bike. That’s not because the motor doesn’t feel powerful enough, but because both the Drive S and the Drive S Mag offer a very natural ride-feeling. If it wasn’t for the permanent low-level buzzing-noise of the motor you’d feel a bit like Nino Schurter on EPO. The Brose Drive S Mag delivers its power almost instantly and you won’t even notice it engaging. When the motor decouples completely at the 25 km/h threshold, it happens so smoothly that the transition is almost imperceptible. And what about that painful Bosch-like resistance? Nope, thanks to the belt drive and two freewheels this is not the case!

A number of new sensors in Brose’s new motor help measure the rider’s input with even more precision. The engineers also developed a new support mode which uses real-time torque and cadence data to limit the power output. When riding in the new Flex Power mode, the motor responds quickly to your input and delivers lots of power even at low cadence. In addition you can on the motor to deliver maximum power even at very high cadences. If you need to pedal hard uphill to build up momentum to pass an obstacle, you will quickly reach a cadence in excess of 90 rpm. In similar circumstances, many of the other motors from the competition — for example the Yamaha PW-X — tend to run out of steam and start to feel like they’re suffering a substantial loss of performance. But just like a Shimano STEPS E8000, the Brose Drive S Mag still pushes hard and helps you overcome the obstacle.

The Brose Drive S Mag is a real cherry picker. It combines many great features of other motors in one package, without succumbing to any weaknesses.

On steep climbs the motor provides efficient, powerful and very predictable support at low speeds. This prevents the wheels from spinning on slippery surfaces like wet roots or loose rock-sections. When riding at full steam in the maximum support-level, the Drive S Mag is so powerful that it will cause the rear wheel to spin out of control and the front end to rise on tricky climbs if you don’t pay attention. Having said that, the motor delivers enough power for technical steep uphills in the second-highest support mode. “Full throttle” in the Flex Power mode only makes sense on forest paths, on which you’ll be cruising at 25 km/h without any problems — provided it’s not too hot on that day. When riding under full load on very hot days, the Drive S Mag suffers and you may experience a temporary reduction of power. However, Brose’s overheating issues from the early days seem to have been addressed.

With the new Drive S Mag Brose’s engineers have successfully managed to combine all of the best features of existing systems and transplant them into a new motor. The Drive S Mag is light, compact and gives bike manufacturers a lot of freedom with their frame designs. Even at low cadence, the Drive S Mag gives you a mighty push and allows you to cruise relaxed — it reminds us a little of the Yamaha PW-X. But unlike most of the motors from the competition, the Brose doesn’t run out of steam at high cadences and easily keeps up with Bosch’s Performance CX motor. The new magnesium motor has inherited the natural drive-feeling of the Drive S.

The new Brose Drive S Mag is a true godsend for the electric mountain bike world. It’s compact, light and very powerful — this should allow manufacturers to create even better eMTBs in the future. On the trail it managed to convince us with great amounts of power and a very natural ride-feeling. Whether you’re riding relaxed or pushing full steam ahead, the Brose Drive S Mag is impressive both on forest paths and demanding technical terrain.

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This article is from E-MOUNTAINBIKE issue #015

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Words: Photos: Valentin Rühl