Bosch’s latest electric mountain bike motor, the Performance Line CX Race Limited Edition, is claimed to provide support for up to 400% of the rider’s power. It does this, according to Bosch, while slashing the claimed 2,900g weight of the standard Performance Line CX unit by 250g.
Although the new Race version of the Performance Line CX motor has the same 85Nm torque and constant 250W power rating as the standard model, this 400% increased assist is delivered from the initial pedal stroke through to the limiter of legally required speed.
Further tuning has been made so that the engine now offers usable support “even at [pedalling] speeds above 120 rpm”, where motor assistance generally runs out of steam.
The speed at which the engine growl is delivered adds to the increased power and extended assist. Motor response times have been sped up to the extent that Bosch says “only those who have [a] precise riding technique can control the direct response and power of Race mode.”
The new motor is compatible with the Bosch eBike Flow smartphone app. As with other Bosch Smart System motors, the downforce and how it responds to rider inputs, as well as other parameters such as maximum speed and torque, can be adjusted.
For the CX Race motor, app-based adjustments are limited to Turbo and Race modes, where Bosch’s impressive eMTB and Tour+ modes that adapt to rider input remain unadjustable. Gone is the Eco setting, however, emphasizing the new unit’s “race-focused eMTB” credentials.
Another racing bowstring from Bosch is the reduced unit weight, claimed to be 2750g. That’s just 150g more than Shimano’s EP-8 and the same as Yamaha’s PW-X3, fitted to Giant bikes, among others.
Bosch claims that this reduction will “optimize the handling of the eMTB on demanding trails” and that “the drive unit can be perfectly integrated into a sporty, slim frame design and enables particularly agile handling”.
To reduce weight, Bosch has “optimized” some of the internal component materials, although it did not disclose details.
Physically speaking, however, the new Performance Line CX Race is the same size and shape as the Performance Line CX engine.
Aesthetically, the two are distinguished from each other thanks to the “graphite gray metal finish” of the magnesium casing and the “logo and accent colors”.
Asked about the “limited edition” moniker to the name of the CX Race engine, Bosch said it “will be available in small quantities,” but did not comment on how many units will be produced.
We at BikeRadar doubt that Bosch will spend all that time and money developing a limited time motor and tuning, and we think it’s likely that the new motor will continue to be produced and specified on bikes in the future. .
Electric mountain bikes equipped with the Bosch Performance Line CX Race motor
Bosch was unable to provide a definitive list of manufacturers and bike models equipped with the Performance Line CX Race motor, but said “approximately 20 well-known manufacturers will specify the new drive unit.”
Since Bosch claims the motor is “designed for race-oriented eMTBs,” we think it would be safe to expect to see it fitted to high-end e-MTBs from Trek, Mondraker, Scott and others.
First impressions of the Bosch Performance Line CX Race motor
Before the official launch, Alex Evans tested the new Bosch Performance Line CX Race motor on his local trails in Scotland’s Tweed Valley. These are his first impressions.
The motor was installed on a Trek Rail 9.8 XT Gen 3, which is the brand’s latest long-travel enduro electric mountain bike.
Trek claims a 9.8 XT Gen 3 medium rail with a Performance Line CX motor weighs 23.4 kg (without pedals, tubeless tires). The Rail 9.8 XT Gen 3 I used to test the new motor tipped the scales at 23.6 kg (medium, without pedals and tubeless tires).
Some weight differences are unavoidable, but the weight savings of the CX Race engine were not apparent with this particular test bike.
On the track, Race mode ups the ante when it comes to sheer power.
It’s best described as an enhanced Turbo mode; the power comes stronger, sooner and lasts longer.
However, for people who have ridden the Performance Line CX, there is a real familiarity with the motor assist as it mimics rider input. The increase in pedal power is equivalent to a satisfying increase in engine power, but now there’s an extra sharpness.
Adjust the sliders to the right in the Flow eMTB app and that sharpness is increased, where even the lightest pedal presses deliver incredibly fast power.
This motor input is maintained up to the assist speed limit with no noticeable dips or flat spots. The claims of increased peak power add up, and the Race mode certainly delivers on Bosch’s promise of “uncompromising performance” when climbing.
Overshoot (how much and for how long the motor provides assistance after the rider has stopped pedaling) has also been increased on the CX Race.
It feels great on technical uphill trails, where tackling rocks, roots or steps is made easier because motor power is fed to the rear wheel for longer after the rider has stopped pedaling.
It’s the same story on flatter descents, where a half or even a quarter turn of the crank engages the motor. It allowed me to either pick up speed quicker or hold it in sections where I’m usually unable to complete full crank turns.
However, when the trails got steeper with lots of braking, I found the extended, more responsive overshoot to be a bit problematic.
Even adjusting the angle of the pedal cranks by pedaling forward a quarter turn – something cyclists do unconsciously when descending when entering turns, adjusting their balance or avoiding rocks and other obstacles on the ground – activated motor assistance.
It was a little off-putting in scenarios where I was hard on the brakes, trying to slow down rather than accelerate.
Switching the engine from Race to Turbo solves this problem because Turbo overshoot is less aggressive. However, changing modes while going through technical sections is more than tricky, and one wonders if this technique is practical on the trails.
Most likely, riders will have to decide if they want the increased power of Race mode, or the control of Turbo or less. This, of course, will be dictated by the terrain they ride on.
Reducing the sensitivity of Race mode in the eMTB Flow app also helped, but this dampened the uphill performance of Race mode and is likely a compromise that most riders looking to take advantage of the extra power won’t be willing to. to do.
How does the new Bosch Performance Line CX Race motor compare to the Bosch Performance Line CX and Shimano EP-8 motors?
Back-to-back testing with a Performance Line CX engine reveals the Race version to be faster.
On a 400m long, 60m ascent, the new motor was three seconds faster than the old when both were ridden in their maximum assist modes with the same power output and heart rate throughout the entire climb. duration of the climb.
In terms of feel, the Race mode increases power at lower, lighter rider inputs compared to the CX’s Turbo setting. Towards the top of the engine the difference is less marked, but the Race engine is stronger up to the rev limiter, compared to a slight slowdown felt with the standard version.
Compared to the Shimano EP-8, Bosch has taken the assist to the next level. The CX Race feels much stronger than the Shimano when both are set to their maximum support levels.
After doing several road drag races with friends who are 30kg lighter, on EP-8 engines, the power of the CX Race was so strong that I was able to keep up with them and pass them. Usually I am unable to keep up with them, let alone overtake them.
It certainly cements the CX Race’s absolute performance credentials as a class leader, but it takes more time with the engine to gain true mastery of its performance.
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