Bosch Performance SX: Bosch's new e-bike motor for light bikes put to the test
Update January 2024: We have now been able to test five different bikes with the new Bosch Performance SX light motor and gather extensive practical experience in a wide range of riding situations. Not yet familiar with the Bosch Performance SX or looking for basic information on riding behaviour or performance in the lab? Then scroll on here.
Light E-MTBs have been the hot topic in the industry for years. Fazua showed with the Evation the first suitable drive at that time, Specialized made the category big with the Levo SLShimano's EP8 is used in light bikes from Orbea until Red deer and most recently the new drives Ride 60 from Fazua and HPR 50 from TQ light bikes a new lease of life. However, motor giant Bosch, of all companies, has so far been left out.
Now the Swabians are finally presenting their first light drive and it really packs a punch. With a peak output of up to 600 watts, the e-bike motor should deliver as much power as the large Bosch Performance Line CX, at least for a short time, but be significantly lighter. This would put it well ahead of other light drives in terms of performance. The Performance Line SX also aims to score points in terms of ride feel and noise levels. To achieve this without the drive overheating or immediately running out of battery, Bosch is focussing on another trend theme: Artificial intelligence.
The Bosch Performance Line SX: The facts at a glance
- Continuous load: 40 Newton metres / 450 watts motor power (manufacturer's specification)
- Short-term peak values: Up to 55 Newton metres / 600 watts motor power (manufacturer's specification)
- Motor weight: 2.07 kg (EMTB measured value)
- New battery: Compact Tube 400 Wh, 2075 grams (EMTB measured value)
- Range extender Power More 250: 250 Wh
- Q-factor: 172 mm (EMTB measured value)
- Part of the smart system
- Compatible with all corresponding batteries, controls and features
Clever little chap - how the Bosch Performance Line SX motor works
Is the world really turning at such a pace that - regardless of age - we can no longer really keep up? A few months ago, the topic of artificial intelligence popped up. No sooner have we come to terms with the fact that AI will eventually arrive in our own lives than Bosch pushes its new Performance SX light motor through the door. And the way it works makes it clear: it's got AI in it! With a weight of 2.07 kilos and a maximum output of 508 watts measured in our lab test, the Bosch SX sets a new benchmark. Bosch even claims 600 watts of peak power. Never before has there been so much power per kilo. But how is such a compact motor, with a small battery to boot, supposed to cope with such power? This is exactly where AI comes into play.
At Bosch, the software has its own adaptive will. The prerequisite for delivering full power is that the AI interprets the average rider performance, the current force on the pedal and the cadence in such a way that it gives the go-ahead for the short-term turbo. When Fazua Ride 60 as well as the TQ HPR50 in the Red Deer R.X 275 you press a turbo button to get extra power. Not so with the Mini-Bosch. The SX decides for itself whether to give the driver normal light power or real turbo boost.
Bosch Performance Line SX: Power only when it's really needed
The idea: the rider only gets the right amount of power when they really need it - without having to worry about operating a boost switch in a tricky riding situation. In order to make the right decision, the software constantly detects the rider's torque and cadence. Only when both parameters exceed an average value is the turbo ignited. In practice, this happens imperceptibly - almost like an extended E-MTB mode. If you give a lot, the motor also gives a lot. What's new here is that the motor adapts to the rider's power and riding style. This means that not only super athletes with Schurter legs can call up the maximum power. It also prevents such powerhouses from riding at full throttle all the time and draining the battery in fast motion - and perhaps even overtaxing the motor. This also means that depending on the average riding style on the tour, relaxed or full throttle, the drive can react differently to the rider's powerful acceleration. So much for the theory.
Quiet and easy to modulate: how the new Bosch SX e-bike motor rides on the trail
And in practice? On flat terrain, the e-bike motor is quite quiet with little power input and only pushes forward gently. The riding noise is well below the level of the Bosch Performance Line CX, but the mini-Bosch is not as quiet as the class leader TQ. As the terrain becomes steeper and the rider's input stronger, the noise increases to an audible but not unpleasant hum and the assistance power increases significantly. We really liked how quickly the power is applied when setting off and how smoothly and imperceptibly the Bosch SX drive fades in and out. The electric motor hugs the foot really well and can be modulated excellently. In this respect, Bosch is setting new standards with the SX.
At high cadences (beyond 90 RPM), the motor is definitely more powerful than both the Fazua Ride 60 (also with Boost!) and the Shimano EP8 RS - the previous powerhouses among the light drives. However, the peak power is only available for a short time. The fact that the motor gradually reduces the power again is noticeable after just a few seconds. And in some situations you feel completely let down by the AI. Because on really steep, technical climbs, where high cadences are not possible, there is very little thrust. No matter how hard you pedal. Unfortunately, these are the moments when you want power. Pushing the e-bike over a step or a root at a low cadence is sometimes more difficult than with higher-torque drives.
Our laboratory analysis below shows that this is not due to a weakness in the software, but simply the character of the power delivery. In terms of torque, the Bosch Performance Line SX is rather mediocre. Obviously, even without a lab test: The little Bosch SX rattles on trail descents. As with its ample power, it has obviously taken an example from its big brother, the Performance Line CX, in this respect too. A pity, really.
Our test bike
Bosch provided us with a prototype from a German bike manufacturer to test the Performance Line SX. There is no official information or release date for this 150 mm bike yet. What we can say: A Compact Tube 400 is permanently installed in the full carbon frame. The scales in the EMTB lab stopped at 18.3 kilos - and that with very high-quality and robust all-mountain equipment. Riding fun? Absolutely there!
Power only at high cadence: The Bosch SX motor on the test bench
The special characteristics of the Bosch SX motor present our laboratory team with a particular challenge. This is because constant operation, as is usual on the test bench, only elicits very tame values from the clever little chap with his intelligent software. This is shown by the solid lines in the first diagram.
A maximum of 39 Newton metres and an output of a good 300 watts at a cadence of 80. These values reflect what the motor delivers in constant, moderate riding mode. In order to stimulate the AI, we deliberately controlled the new SX e-bike motor dynamically on the roller dynamometer in the PT Labs laboratory and thus came closer to its maximum values. 50 Newton metres and 508 watts were on the clock after our test runs. Bosch itself states that the maximum values should be even higher. The torque is 55 Newton metres, the power exactly at the level of the Performance Line CX drive, which would mean around 565 watts in our test procedure.
In practice, it is quite possible that the software reacts to an explosive acceleration with even more power. The dashed lines in the diagram above would then be slightly higher. However, these peak values can only be called up in certain situations and not permanently. The software not only recognises the two states A or B. Rather, the range between the lines is selected dynamically - depending on how the AI interprets the current driver input in relation to its average values. This is not noticeable in driving practice, resulting in a very dynamic and never abrupt driving experience. The engine power always remains excellently modulable.
Best peak power, but little torque: The new Bosch motor compared to the competition
The second special feature of the Performance Line SX is also clearly evident on the test bench. The maximum output of over 500 watts puts all other light motors in the shade. However, it is important to understand that this value only really comes into its own at very high cadences. At low cadences and in constant operation, the SX Bosch motor provides less thrust due to its comparatively low torque. Fazua Ride 60 and Shimano EP8 RS in particular deliver noticeably and measurably more torque.
The competitors of the Bosch SX in a detailed test:
From the test bench to practice: Fazua wins points with a slow kick
In addition to the test bench values, the practical experience of all our test drivers clearly shows this. The diagram above illustrates this. In constant operation, the Bosch Performance Line SX can only outperform the Fazua Ride 60 (without boost function) at a cadence above 90. At slower pedalling speeds, the Fazua is clearly above SX level. Even with dynamic rider input, the small Bosch doesn't come close to the values of the Ride 60. In practice, this is always clearly noticeable when the riding situation does not allow for a high cadence. This is often the case on technical climbs. Bosch's new SX drive then only pushes moderately over edges and obstacles - despite the record maximum power.
Update January 2024: Long-term check of volume, power and range
We have already tested a total of five bikes with the Bosch Performance SX in various riding situations. These include touring-orientated e-mountainbikes such as KTM's Macina Scarp SX, all-rounders like the new Centurion No Pogo SL and long-travel enduro bikes like the new Ryvon LT from Conway. Many of the initial impressions that we were able to gather with the new light motor from Bosch proved their worth.
The particular strength of the Bosch SX, even in long-term operation, is its dynamism. When the riding situation is right, the dwarf drive from Reutlingen impresses with its astonishing performance and puts a big grin on the rider's face with its lively acceleration. Even if it doesn't release its maximum power permanently, the Bosch is in a different league to the minimalists in the light segment such as TQ and Specialized. Riding tours together with conventional E-MTBs in the 85 Newton metre class is therefore rarely a problem with the Bosch SX if you are fit enough. The Bosch never tries to hide its nature as an E-MTB motor. The extremely dynamic power delivery is absolutely successful, but the buzzword "discreet support" would never come to mind.
Especially as the Performance SX is quieter than Bosch's CX power motor, but the drive noise is by no means inaudible. The SX reacts particularly strongly to the riding situation. With little assistance, the lightweight Bosch is often quite quiet and there are some real aha moments. However, the sound is not very discreet when its high power is utilised. Unusual: On longer tours and longer climbs, the drive gets louder over time. It is then clearly audible even with moderate support. If you're seriously interested in the SX, you shouldn't just rely on a car park test at the dealer when it comes to sound. Overall, we would place the SX in the middle of the light category in terms of volume. It is quieter than the classic CX, but it doesn't come close to the equally powerful Fazua. And the whisper TQ is in a different noise league anyway. Although Bosch has been able to reduce the rattling downhill a little compared to the CX, it remains clearly audible on all Performance SX models that we have tested so far.
Little torque, range in the light midfield
The fact that the Bosch SX is no revelation in terms of torque has also been confirmed. It can only really play its trump card of high peak power at a high cadence. When it comes to pushing over obstacles with a low cadence on technical climbs, motors like the Fazua Ride 60 are better positioned. The competitor from Ottobrunn is also slightly ahead of the SX in terms of performance with low rider input. This doesn't make a big difference in touring practice, but the difference is measurable, as our range test shows, for example. Under identical test conditions - 90kg rider weight, 80 cadence, 150 watts pedalling power - the Fazua travelled at an average of 12km/h instead of 11km/h.
In terms of range, the Bosch Performance SX with its 400 watt-hour battery is well positioned and climbs 1000 to 1100 metres in the standard test scenario mentioned above on a steep asphalt climb. However, intermediate sprints are not built in here. If you push the SX to peak performance, you will have to reckon with less range in practice. Fazua's Ride 60 is clearly ahead of the SX with over 1200 metres of climbing and is also faster with full support. In our test, Specialized's SL 1.2 drive unit achieved almost the same range as the SX with its 400 watt hour battery, even with a smaller 320 watt hour battery, but with a lower power output. TQ's HPR50, with 360 watt hours in the battery, usually brings up the rear in terms of range and speed. To give you an overview, we have listed some of the most relevant comparison drives with their average ranges below.
Comparison of ranges
- Bosch SX: 1060 vertical metres at approx. 11 km/h
- Fazua Ride 60: 1280 vertical metres at approx. 12 km/h
- Specialized SL 1.2: 1020 vertical metres at 10.1 km/h
- TQ HPR 50: 930 vertical metres at 9 to 10 km/h
- Bosch CX: 1950 metres in altitude at approx. 14 km/h
Conclusion Christian Schleker, test author EMTB
With the SX, Bosch has created a motor with its own character. A light motor has never been so lively and powerful. However, the AI-controlled superpower has logical limits. Due to the moderate torque, not much of it can be felt at low cadence - then other light drives can do more. The noise level is on a par with the competition and the driving experience is outstanding. Unfortunately, the SX rattles downhill.
Strengths:
- lively and dynamic driving experience
- Extreme peak performance
- High fun factor
- great modulation
Weaknesses:
- could be more compact
- Torque and power at low cadence
- Noisy in some driving situations, rattles downhill
Driving performance instead of a beauty contest: An interview with Bosch CEO Claus Fleischer
EMTB: Now Bosch also has a light motor with the Performance Line SX. How important is the minimal-assist bike segment for Bosch?
Claus Fleischer: We consider this segment to be very important, as it combines the advantages of two worlds like no other: a particularly natural riding experience on lightweight e-bikes with geometries and looks close to conventional bikes, coupled with the opportunity to experience the maximum riding pleasure of a "full-power" e-bike. What's more, e-biking and e-mountain biking are becoming increasingly specific and customised. The classic e-bike systems and therefore also e-bikes have become increasingly heavier due to higher battery capacities and more power. This also means that lighter e-bikes can only be realised by reducing the maximum power. We have now transferred the typical Bosch quality, reliability and riding performance to this relevant category. Low weight meets high riding pleasure: that's the Performance Line SX!
What can the new Bosch motor do that other light drives can't?
The SX is a small power package. We can get the finest riding fun out of just two kilograms with more than 400 watts and up to 600 watts of maximum power. In addition, the SX sets standards in terms of response behaviour and natural riding feel. It is therefore probably one of the most powerful drive units in this still young market segment and is characterised by a special riding experience, especially with the dynamic Tour+, EMTB and Sprint modes.
The installation space is rather large compared to other light drives. What's behind it?
At around two kilograms, the SX is the lightest and smallest drive unit in the Bosch product portfolio. It was important to us to achieve an optimum balance of performance, noise and thermal derating with the SX, and thus to inspire customers. The "beauty contest in the 2 kg segment" may go to other systems; the noticeable riding performance is more important to us.
Another special feature is the intelligent engine control, which only delivers maximum power in special situations. What exactly is the idea behind it?
When developing the SX, we addressed the triangle of driving performance, optimised derating behaviour and maximum range with a small battery. The solution for us was a new type of software that always provides the rider with maximum torque or maximum power exactly when it is actually needed.
The drive noise is much more pleasant and quieter than with the Performance Line CX. How did you achieve this?
To match the performance of the SX, we specifically opted for a different motor-magnetic circuit design and a matching gearbox concept, which significantly reduces the perceptible noise of the drive. We have also focussed more on the design of the gearbox and in particular the tooth geometry and tooth surfaces. As a result, we have now been able to virtually eliminate noise influences from the gearbox.
In our ride tests, the motor rattled on trail descents. What makes it so difficult to remedy this problem, which many other engines also have?
Basically, this is a vibration caused by the chain, which can lead to transmission noise in certain riding situations, for example on a root carpet. With the SX, we have already succeeded in significantly reducing this noise and we are working on eliminating it completely in the future.
