Bosch Performance SX in laboratory and practical tests: Powerful thrust in a compact box

Ever since Bosch entered the market with the Performance SX, the light e-mountainbike segment has been gaining massive momentum. Almost every well-known manufacturer now has a light e-mountainbike in its range. The Bosch interpretation of a light drive is special. Visually, the SX is not very different from its big brother, the CX, making it almost clunky in comparison to the Light. However, the SX has by far the highest peak power of all Light drives. Bosch even speaks of the same maximum power as with the large Performance CX. We tested how this can be - and whether the SX can fulfil its full-bodied promises - in the laboratory and in practice.

The facts about the Bosch Performance SX

• Weight: 2.1 kilos
• Battery sizes: 400 Wh (2.1 kg)
• Optional: Range extender with 250 Wh
• Drive levels: Eco / Tour (+) / EMTB / Turbo
• Performance data (max.) from the laboratory: 49 Newton metres, 521 watts
• System updates possible via the app

The character of the Bosch Performance SX

The modulation of the Bosch unit is outstanding. It literally hangs on the foot, reacting directly and yet very smoothly to the rider's impulse. No other e-bike motor can do this so brilliantly. Another unique feature is the progressive design, which makes the thrust particularly dynamic. The more the rider accelerates, the more the SX accelerates. Anyone familiar with Bosch's EMTB mode will recognise this effect. With the SX, this phenomenon is even more drastic. The background noise of the Mini Swabian is very different. If you pedal comfortably away from the car park, the SX is almost inaudible. Under load, however, it is almost as loud as the power classics from Bosch and Shimano. Unfortunately, it has also inherited the annoying rattling downhill from them.

The power delivery of the Bosch Performance SX

The hard facts sound too good to be true: 521 watts on the test bench, which puts the Performance SX among the power engines. But there is a but. The small Bosch only develops its full power at very high pedalling frequencies and lively starts. If you pedal at a leisurely pace, you get significantly less thrust than, for example, from the Fazua Ride 60. With this sporty character, Bosch wants to inject its lightweight (2.1 kilos) with real e-bike thrust and uphill flow.

However, the concept only works to a limited extent on difficult climbs. You can gain momentum dynamically and master many a nasty step. However, if the riding situation doesn't allow for a high cadence, the SX lets you down a little. The more technical the climb, the less convincing the SX is. High cadences also increase the risk of the cranks bottoming out. In some situations, this makes the Mini-Bosch feel a little unharmonious. This is because it is easy to crank a high cadence on shallow forest tracks. Then the motor feels extremely powerful. If it gets steeper and more difficult, the cadence also drops - and with it the power of the motor. You have to consciously pay attention to high cadences. Even if you like high cadences: The SX encourages unnaturally fast cranking, as it continues to increase power well above 100 rpm.

Display and remote

The "little" Bosch is compatible with all the components of its big brother. Including all displays and batteries. However, the vast majority of bike manufacturers rely on the minimalist system controller with LED display in the top tube, especially for the SX motor. This fits in with the sporty and minimalist approach of the light bikes. A Kiox display can also be combined as an option, which is also available for retrofitting. A special feature of the slimline mini-remote: it works wirelessly, something that hardly any other manufacturer offers.

The batteries for the Bosch Performance SX

Bosch has introduced the Compact Tube 400 (2.1 kg, 400 Wh) to match the small motor. Even though the motor is theoretically compatible with all other Bosch batteries up to 750 Wh from the Smartsystem, all E-MTBs with an SX motor currently come with the 400 Wh battery. Many bikes have the battery permanently installed. However, the option of the 250 range extender Bosch Power More 250 is particularly exciting. This makes it easy to extend the range.

App and connectivity

The little Bosch is also very close to its big brother when it comes to the app. Like the CX, the SX also uses the Bosch eBike Flow app. Fine-tuning the support levels, using the smartphone as a key, navigation and updates "over the air": there are many functions here. However, communication with third-party devices such as Garmin bike computers is also significantly limited on the SX. Here you have to rely on the infrastructure and components from the Bosch portfolio.

EMTB review of the Bosch Performance SX

Strengths

• Dynamic thrust
• High maximum output
• Excellent modulation

Weaknesses

• Not very compact in a light comparison
• Loud under full load
• Rattles downhill

Conclusion on the Bosch Performance SX

Sporty light motor with high peak power, excellent modulation and dynamic thrust. Rewards sporty commitment from the rider and really revs up at high pedalling frequencies. But rather large and sometimes noisy. Too bad: rattles downhill. Made for all those who are looking for a lightweight bike but don't want to do without the e-bike feeling and uphill flow.

Bikes with Bosch Performance SX

Bikes with Bosch's Performance SX are literally springing up like mushrooms. Although the small Bosch is the youngest light motor on the market, the selection of models is already quite large. Industry giants such as Bulls, Canyon, Cube and Flyer are also already using the SX. The links provide all the information and details on some e-mountainbikes with Performance SX:

• Bulls Sonic Evo AM SX
• Canyon Neuron:On Fly CF
• Centurion No Pogo SL
• Conway Ryvon
• Cube AMS Hybrid One44
• Flyer Uproc SL:X
• KTM Macina Scarp SX
• Nicolai Saturn Swift
• Norco Fluid VLT