Bosch Performance Line SX Review

The last time I rode an eBike in the lightweight category, was when I was pregnant. Tired, out of breath and wanting to ride my bike up hills that demanded more than I could give, I realized that maybe eBikes might finally find a place in my life. However, I previously found lightweight bikes to be a bit…anaemic. While they can pack a punch in turbo mode, the low and limited support modes left me a little wanting in terms of the level of support and engagement I needed.

After a year or so, I'm still curious about eBike, but I've found the more powerful eBikes to be more in terms of travel and the 'pow' on the trails I ride and study I want. A hiker at heart, the Bosch Performance Line SX drive unit is one that – on paper – fits the bill, delivering a mountain biking experience with all the support you need, when you need it. I tested the drive unit inside the Canyon Neuron ON:Ffly CF 7. From bike racks to secret squirrel lanes and baby dumpsters, we've done it all.

A Closer Look

But first, why the SX drive unit? The Bosch SX drive unit is designed as a model that prioritizes the riding experience, shaving weight from the more torque-driven CX line drive unit, reducing bulk to deliver smooth lines reminiscent of the aesthetics of a sound bike. The slimline magnesium casing leads to a 2kg unit weight, a reduction of almost a kilogram compared to the new generation CX at 2.8kg. The thin, thin casing results in a small Q factor (or width between the cranks), allowing for a natural riding action similar to an analogue mountain bike.

In terms of battery life, the Bosch Performance Line SX drive unit is paired with a 2kg, compact 400-watt hour CompactTube 400 Battery. The CompactTube is the highest capacity of all Bosch batteries and charges to 50% in 1.5hrs and 100% in 3.5hrs, making it perfect for use on your travels or in an overnight flashpack. The lightweight package of the SX drive unit allows the bike to retain the 'feel' and handling of an acoustic trail bike with the power of the drive unit. For reference, the bike we tested weighs less than 20kg with pedals.

The 400Wh battery is on the small side for long trips, so for long-distance warriors, the PowerMore 250 range extender (weighing 1.5kg) takes you up to 650-watt hours of battery life, essentially giving you the cream of the crop for an eBike. This is placed in a bottle cage, so prepare your pack for big days out.

The SX drive unit is designed specifically for lightweight eMTBs but still uses the high 600W power output found in the creamier CX unit. The SX has a reduced torque of 55Nm (compared to the CX's 85Nm), and reaching the maximum 600w requires a cadence of more than 100rpm. At 70rpm, the maximum output power of the SX unit is 400w: still nothing to sneeze at, but a very different user experience from the 600W delivered at 70rpm with the CX drive unit. This cadence-driven power delivery is the main difference between the two drive units.

The Bosch Performance Line SX's power delivery is described as sensitive, requiring the rider to shift and focus on pedaling through the terrain instead of engaging gears. This may disappoint those who prefer to turn on the eBike and grind at 40rpm upwards, but for those who enjoy the feeling of oneness and the joy of effort that cycling brings, the SX drive unit allows it. an experience that immerses the passenger as the pilot and engine. As for the top speed, of course, it reaches 25km/h. The maximum support level comes out to 340%, and the SX drive unit retains a smart navigation feature, activated by the bar-mounted Mini Remote.

Helpful light indicators tell you when you're in Eco (green), Tour+ (blue), eMTB (purple) or Turbo mode: all available modes for a Bosch mountain bike. You can also change modes using the System Controller, in addition to the Mini Remote, and the SX system is still compatible with Kiox units. Want more customization? Of course! This is, after all, a Bosch product, and their excellent Flow system allows the rider to customize the levels of support and torque in each mode for an individual ride experience.

On the road

Bosch wanted a quieter drive unit with the release of the Bosch Performance Line SX, and they delivered. While the engine still has a slightly noticeable 'whirrr', which is more noticeable on the turbo, it's not distracting. You can feel the weak and uncoordinated engagement of the drive unit when traveling at a speed of around 25km/h or when crossing tracks, however that is not distracting and marks a departure from the previous generation Performance Line CX which is more responsive. drive unit.

Low torque is the main difference between the Bosch Performance Line SX and other drive units. With 55NM of torque, it's not sporty or ideal for sprinting off the line, but this results in a bike that delivers what it puts in. This translates to less skipping or dragging in the writing material and lower speed movement of the trace. With the engine tuned to provide more assistance at higher cadence, I found that the lower torque actually gave the rider a more compact, authentic riding experience and a smooth, natural power delivery.

In short, the feel of the Bosch Performance Line SX is one of amplification rather than raw power, for those who like to plow the trails with little effort on a cream-filled eBike this may not be the experience you're looking for.

However, this does not mean that the bike has no blood at all; after all, it still has a maximum power of 600W. The way divvy's the watts out, however, changes the behavior of the rider. For example, on my first ride I went out and like any rider with a new eBike: I found a very consistent, direct position to point the bike up.

How did it go? I managed 850m vertical in less than an hour in only 13km. At first, it was a strange feeling to get used to, hitting immovable mountains (well, immovable on an analogue bike) full of children's head stones and no separate line. On an analogue bike, you'd be pedaling with a low cadence to try to grind and maintain momentum, the SX doesn't thrive on grinding. In fact, it offers very little help with that kind of trolling behavior.

Instead, I had to change my behavior and move around whenever the surface was facing upwards, which seemed to be incompatible with such gradients, however it didn't take long to adjust and get more power from the unit.

Apart from this, on long drawn out climbs (think 10+ minutes) it is difficult for the mortals among us to maintain a cadence >100 as the aerobically taxing cost is too high. While still helpful at low cadences, to get the most out of the drive unit it's best to swing to win.

Considering the mountain bike cover, it would be wise to reduce the cadence required to get the full power in future drive unit updates, even if a modest drop to 90rpm would make a big difference to the rider's experience while maintaining the smooth and compact feel of the SX Unit.

When hitting technical, consistent trails, the drive unit really comes into its own as you find that rhythm and flow of pedaling, gathering speed and pedaling ahead of obstacles, and resetting to a neutral cadence. It was during these times that the drive unit really flourished, just a normal route ridden on winding tracks. The SX's drive unit works a lot like the ride itself, but better.

Spoke distance is difficult to define as absolute: like everything related to mountain biking, it depends on many variables. As a 63kg rider, I represent a good average female rider or light weight male rider, this will have a big impact on the battery and the feeling of the power delivery when the position is pointing up. In EMTB without a long distance, we managed to go around the hills for 40km. With the PowerMore range extender I actually ran out of time on my long battery drain trips. After more than three hours, 1600m straight and 60km of pony trails, bike park single track and sketchy off piste adventures, I had enough battery left to power the 1.6km/200m climb home and still had one red battery left.

Final thoughts

The Bosch Performance Line SX may not be for everyone, but it is for the dedicated mountain biker who enjoys the feel of an analogue mountain bike with the powerful assistance of an eBike. Instead of the 'power full off the line' experience offered by the CX model, the SX unit's power delivery is more sophisticated, while still packing a punch when it matters.

If you're a rider who wants to cruise to the top of a hill very quickly while going slow, this isn't the drive unit for you, but if you're someone who enjoys the feel and ride of a sound bike. paired with natural-feeling power delivery in a package that could pass as a motorless bike, then the exciting Bosch Performance Line SX could be yours.