The most important facts in brief

When testing Bergstrom's latest model, we were able to gain a first impression of the "Bosch Performance Line SX". The time frame was too short for a full test and the bike was a little overweight at 21.6 kilos. The SX is aimed at light eMTBs under 18 kilos, where the weight saving of the motor - compared to the Performance CX - has a positive effect on handling.

With a weight of around 2 kilos and 55 newton meters of torque, the new SX is a mid-assist motor. With a maximum output of up to 600 watts, it actually plays in the big leagues. Bosch wants to appeal to sporty riders with this motor. Because for it to really take off, it needs a good portion of revolutions under its own power. If you want to be "pushed up", you have to reach for the big brother CX.

In use

The most powerful support mode shows what a motor is capable of. With Bosch, this is the "Turbo". A bike tour usually starts on asphalt, which is how the first ride with the Bergstrom bike began. On flat terrain, the SX accelerates very "naturally" and dynamically, but noticeably more powerfully than other motors with similar torque. You quickly reach the 25 km/h limit. If the road rides steeply uphill, you have to pedal at a cadence of around 95 rpm to keep up the pace. Unfortunately, the engine doesn't like this and becomes quite loud. On a similarly steep gravel road, where the rolling resistance slows down the speed and the cadence drops, the noise also disappears. If you pedal a little more relaxed or use the E-MTB mode (in the factory setting), the noise is limited. The same applies when the SX reaches operating temperature, in which case it is quieter than when it is still cold.

The Bosch Flow app allows you to adjust the support levels individually. If you set the Turbo dynamic to the maximum (5), the motor becomes almost aggressive. If the pressure on the pedals changes, it reacts immediately. In addition, the suspension must be adjusted to the more biting support and the compression stage increased. Very experienced bikers can handle this power, while experienced and less experienced riders can select dynamic level 2 for Turbo and E-MTB mode. This results in a little more bump than in the factory setting, but not so much that the rear wheel spins on wet stones or roots. In addition, the motor then provides consistent power and is less sensitive to fluctuations in human assistance.

Conclusion

The Bosch Performance SX combines two worlds. Its weight enables lightweight e-bikes that are a lot of fun. At the same time, it has a lot of power for its category and delivers more than just a "tailwind" uphill, yet you are not pushed uphill. The motor performs best at a high cadence, but then it drains the battery really quickly. Long tours should be done in E-MTB mode with moderate power input, otherwise the power may not reach the top of the mountain. The SX is the right choice for anyone looking for a lightweight e-bike with plenty of oomph.

Manufacturer

www.bosch-ebike.com