Bosch Performance SX Motor | Electric Bike Report

Featherweight performer

The Performance Line SX motor weighs just 4kg, as does its Powertube battery. Motor plus batter plus controller weigh a nick less than 9 lbs. total. That sounds great, but the implications are impressive. An eMTB built with this Performance Line SX motor and battery have the potential to allow an eMTB maker the ability to produce an eMTB with a higher power-to-weight ratio than anything currently on the market.

For comparison, the Specialized SL 1.2 motor and battery are nearly identical in weight to the Performance Line SX motor and battery; Specialized claims a weight of 2kg for the battery and 1.95kg for the motor, while Bosch claims 2kg each for the battery and motor, a difference of 50g.

Performance wise, the Specialized’s SL 1.2 motor produces the same nominal wattage: 250. However, its torque is almost 20 percent lower, at 45Nm. More dramatic, though is that while the Specialized SL 1.2 maxes out at 320W of power, the Bosch Performance Line SX can deliver almost double that—600W.

Better power at high cadences

One issue that many mid-drive motors have is that they operate best at a fairly narrow range of cadences. They often struggle to produce optimal wattage at cadences below 80 rpm and above 100 rpm. It’s a range that works well for many riders, but for cycling enthusiasts—especially road and gravel riders—their cadences tend to run closer to 100 rpm; for veteran road riders, a cadence of 120 rpm is not uncommon.

Most mid-drive motors see a substantial fall-off in power above 100 rpm, but not the Performance Line SX motor. For this reason, it shows promise for spec in more than lightweight eMTBs, particularly road and gravel e-bikes.

Simple, but powerful, controller

The controller for the Performance Line SX is mounted in the e-bike’s top tube, just behind the head tube, putting it in a location where it is easy for the rider to reach as well as see, but also out of the way of knocks and dings to decrease the chance of damage in a fall.

The controller is simple to operate; it features just two buttons: one for power at the top of the panel and another to select PAS level. Unlike many current Bosch systems, the controller for the Performance Line SX gives riders five PAS levels: Eco, Tour, Tour+, Sport and Turbo.

The LED lights for the controller also give riders the battery’s current charge. Five blue lights means 100 percent charged. At 90 percent the display shows four blue lights and one white light, showing a 10 percent reduction in charge.

Of course, Bosch offers more support for riders than that one controller. They offer the “Mini Remote” which is a wireless trigger for the controller so that riders can increase or decrease their assistance without taking a hand off the bar.

Bosch also makes a smartphone app for iOS and Android called Flow which allows riders to fine-tune performance parameters, and also use their smartphone as a security key. The Flow+ premium service adds an alarm and tracking function for riders.

Bosch offers riders a walk mode to aid riders should they need to do some hike-a-bike in steep terrain and they add another feature found in many cars today: hill holder. This feature will prevent the e-bike from rolling backward should a rider need to dismount on challenging terrain.