Let me start by apologizing to Bosch for calling the new Performance CX motor the “gen5”. They insist the new motor is called the “BDU38”. I‘m not sure that’s going to stick as it’s referred to as the “gen5” by several brands releasing a new bike these days.
The batteries too have been updated. Thanks to improved battery cells, we get a new PowerTube 600 battery that is more than 600 g lighter than the old PowerTube 625. And the new PowerTube 800 is about 500 g less than the old 750 battery.
There are 3 batteries for the new Bosch CX motor, all using the 5.6 Ah cells. The battery packs all share the same battery connector. This means you’ll be able to use either battery in combination with both the SX and CX gen5 motors. Provided there is room in the frame of course.
It’s nice being able to combine the parts as one wish. Some manufacturers will let you buy a Bosch CX powered bike with the 400 Wh battery. Combine that with the PowerMore 250 range extender and you’ll have a light and strong bike with extra range when needed. Or you could combine the PowerMore with the big battery for 1kWh+ capacity.
Bosch decided the new PowerTube batteries needed to be grey, or silver. And that’s a wise decision. Having the raw metal finish means they won’t pain the battery. That makes the battery cheaper, easier to manufacture and it’s a bit better for the environment. I can’t think of any upsides to painting a battery that is hidden inside the frame.
Yeah, the motor programming and behavior is new. And, to me, that’s more important than increasing the maximum torque by 5-10 Nm. I’ve said in previous reviews that power is nothing without control. At least not for riding technical trails.
The first Performance CX generations would be a bit jerky when going on and off the pedals on a challenging trail section. This was greatly improved with the Smart System update in about 2022. The Bosch CX gen4 had basically caught up with easily controllable motors such as the Shimano EP8. We have ridden the new Performance CX, but we haven’t compared it directly to the EP8. My initial impression is the new Bosch CX could be the easier to control.
And it seems Bosch have succeeded. The motor activates immediately when we start pedaling. And it does so in a very controlled manner, there is practically no twitching from the motor if you rest your foot on the pedal while stationary. But as the cranks move ever so slightly, the motor is engaged. There is no uncontrolled burst of power as the motor kicks in. If we immediately remove the foot from the pedal, the power is gone, and the motor does do an abrupt or jerky motion.
There has always been talk about natural feeling motors, but what is a natural feel? To me, it’s having a motor that doesn’t do anything your feet doesn’t do. If you feel the motor powering on when you barely ease off the pedals, it doesn’t feel natural. If there is a surge of power when you start from a stand-still, it’s unnatural. The new Performance CX BDU38 (gen5) feels natural. “The pedals are glued to your foot” a Bosch rep said. And I agree the motor seems completely controlled by your feet, with no additional power delivery.
The Bosch rep, Stefan Schlie has been responsible for developing the motor assist modes. He goes on to say that the motor must have the right dose of power and the right timing. There can be no delays and no interruptions of motor power. The timing must be perfect. As a trials rider, he would know what he’s talking about.
This level of motor control is a huge improvement, it allows moves on an emtb that previously were very difficult or even impossible. This might feel like minor and supple changes, but the motor will allow us to do new things on an emtb. This is a big upgrade on the Bosch CX DBU38, it’s a better behaving and more versatile motor.
But if you pedal hard into the same rock garden, pushing extra hard on the final pedal stroke before leveling the pedals to coast. Then you’ll get a big amount of “extended boost”, the motor will keep the bike moving for a short while. But it could be enough to clear an obstacle and start pedaling again. Sure, you might not call it natural. But the Bosch CX is still a natural feeling and easily controllable motor when it matters.
So, how strong is the Bosch Performance CX really? I talked to a Bosch technician, and he drew a power curve for me. I was quite excited to finally see an emtb motor power and torque curve!
We start off at zero Watt when the motor is inactive, and the power ramps up linearly until we reach 600 W at around a cadence of 65 rpm. The first part of the torque curve is flat at 85 Nm. When the motor reaches 600 W at 65 rpm, the torque tapers off with just the right amount so the power output remains at 600 W until over 130 rpm.
Also, I appreciate the reduced motor noise and the absence of motor rattle. The motor noise didn’t bother me that much, it just blended with the sounds from tyres, cables and the chain. But when riding a more silent bike, it just feels more pleasant. I get a sense of relief for every sound that is eliminated. It makes the entire bike feel more solid and well designed.
Motor and battery highlights
So, the new Bosch Performance CX looks similar to the previous one, which Bosch says isn’t actually named gen4 but “BDU37”. The new motor has a maximum torque of 85 Nm and peak power is still 600 W. But the noise level is improved, and the weight has changed. There are a few numbers floating around, but I believe 2.85 kg is correct. That’s about 100 g less than the previous Performance CX.The batteries too have been updated. Thanks to improved battery cells, we get a new PowerTube 600 battery that is more than 600 g lighter than the old PowerTube 625. And the new PowerTube 800 is about 500 g less than the old 750 battery.
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Next generation motors and batteries
The smaller and milder Bosch Performance SX was launched just over a year ago. It had only two motor mounting points, one less than on the CX gen4. And it was a sign of what was to come. The new Performance CX has the exact same mounting points. That’s bad news for backwards compatibility. But Bosch says the new way of mounting the motor should bring advantages as it’s easy designing a frame around it. And I guess this explains much of the weight reduction.There are 3 batteries for the new Bosch CX motor, all using the 5.6 Ah cells. The battery packs all share the same battery connector. This means you’ll be able to use either battery in combination with both the SX and CX gen5 motors. Provided there is room in the frame of course.
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It’s nice being able to combine the parts as one wish. Some manufacturers will let you buy a Bosch CX powered bike with the 400 Wh battery. Combine that with the PowerMore 250 range extender and you’ll have a light and strong bike with extra range when needed. Or you could combine the PowerMore with the big battery for 1kWh+ capacity.
Bosch decided the new PowerTube batteries needed to be grey, or silver. And that’s a wise decision. Having the raw metal finish means they won’t pain the battery. That makes the battery cheaper, easier to manufacture and it’s a bit better for the environment. I can’t think of any upsides to painting a battery that is hidden inside the frame.
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Purion 400 display
Bosch brings out a new display designed for the Performance CX line. The Purion 400 is compact and sits well protected next to the stem, just like the Shimano EP8 display. The 1.6” display provides fitness data and trip numbers such as speed, range and power. Did you notice the displays says "Trail Pro"? That's the new ABS system, we'll get back to that in a separate article.Is the Bosch Performance CX gen5 actually new?
The peak performance numbers are the same and the motor looks similar. Is anything new at all?Yeah, the motor programming and behavior is new. And, to me, that’s more important than increasing the maximum torque by 5-10 Nm. I’ve said in previous reviews that power is nothing without control. At least not for riding technical trails.
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The first Performance CX generations would be a bit jerky when going on and off the pedals on a challenging trail section. This was greatly improved with the Smart System update in about 2022. The Bosch CX gen4 had basically caught up with easily controllable motors such as the Shimano EP8. We have ridden the new Performance CX, but we haven’t compared it directly to the EP8. My initial impression is the new Bosch CX could be the easier to control.
Motor behavior
To achieve this, Bosch tells us they’ve included more sensors in the new motor. There is a new cadence sensor that measures even the tiniest movement of the cranks. And there’s an inertial sensor that measures acceleration, rotation and the angle of the terrain. This is used to determine where and how the bike is riding and adjust the motor behavior accordingly.|
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And it seems Bosch have succeeded. The motor activates immediately when we start pedaling. And it does so in a very controlled manner, there is practically no twitching from the motor if you rest your foot on the pedal while stationary. But as the cranks move ever so slightly, the motor is engaged. There is no uncontrolled burst of power as the motor kicks in. If we immediately remove the foot from the pedal, the power is gone, and the motor does do an abrupt or jerky motion.
There has always been talk about natural feeling motors, but what is a natural feel? To me, it’s having a motor that doesn’t do anything your feet doesn’t do. If you feel the motor powering on when you barely ease off the pedals, it doesn’t feel natural. If there is a surge of power when you start from a stand-still, it’s unnatural. The new Performance CX BDU38 (gen5) feels natural. “The pedals are glued to your foot” a Bosch rep said. And I agree the motor seems completely controlled by your feet, with no additional power delivery.
The Bosch rep, Stefan Schlie has been responsible for developing the motor assist modes. He goes on to say that the motor must have the right dose of power and the right timing. There can be no delays and no interruptions of motor power. The timing must be perfect. As a trials rider, he would know what he’s talking about.
This level of motor control is a huge improvement, it allows moves on an emtb that previously were very difficult or even impossible. This might feel like minor and supple changes, but the motor will allow us to do new things on an emtb. This is a big upgrade on the Bosch CX DBU38, it’s a better behaving and more versatile motor.
Motor overrun
All of this doesn’t mean the motor overrun, or extended boost, is gone. There is nothing natural about having a motor that continues to push after we stop pedaling. But Bosch pulls this off. Depending on how you pedal, you may have lots or no overrun. When track standing in a rock garden, you will most likely only do short pedal strokes before backpedaling. And you will likely not push very hard. Now the motor is easy to control without any unforeseen shoves.But if you pedal hard into the same rock garden, pushing extra hard on the final pedal stroke before leveling the pedals to coast. Then you’ll get a big amount of “extended boost”, the motor will keep the bike moving for a short while. But it could be enough to clear an obstacle and start pedaling again. Sure, you might not call it natural. But the Bosch CX is still a natural feeling and easily controllable motor when it matters.
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Hill start
Do you ever struggle when starting a steep climb mid-hill? I can’t really say it’s a huge issue. But the new hill start function is one of those things you might not see the need for, but soon come to love after having tried it. When getting on the bike in a steep section, hold down the “minus” button and the display will let you know that hill start is active. If you were holding the brake, you can let it go and the bike will remain stationary. The system is ready to go and waiting for you to start pedaling. You’ve got the full 85 Nm available immediately.|
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Much improved noise levels
The first thing we checked was the motor rattle noise. Had Bosch been able to reduce the rattle? No, they didn’t just reduce it, the rattle is completely gone. We lifted the bike and smashed it to the ground, we rode stairs and rock gardens, and the motor was quiet! And the motor whine, the noise when the motor is pushing hard at higher cadence, was greatly improved. We couldn’t compare the new Bosch CX to other motors, but I believe it’s more silent under load than the Bosch SX 55 Nm.Motor power
This new motor isn’t stronger than its predecessor, but that doesn’t mean the 2025 Performance CX won’t develop over time. The old CX gen4 started off as a 75 Nm motor with rough characteristics in Boost mode. First it was updated to 85 Nm and then the Smart System refresh brought more refined motor behavior. I wouldn’t be surprised to see the latest CX develop over time.So, how strong is the Bosch Performance CX really? I talked to a Bosch technician, and he drew a power curve for me. I was quite excited to finally see an emtb motor power and torque curve!
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We start off at zero Watt when the motor is inactive, and the power ramps up linearly until we reach 600 W at around a cadence of 65 rpm. The first part of the torque curve is flat at 85 Nm. When the motor reaches 600 W at 65 rpm, the torque tapers off with just the right amount so the power output remains at 600 W until over 130 rpm.
My take
After seeing the specs, some might have decided there is nothing new with the CX gen5. We’re used to seeing ever increasing torque figures, but not this time. What do we gain by increasing the power? We’ll be able to maintain pace a bit closer to cut-off speed, at the cost of battery consumption. I prefer the Bosch approach. The motor shouldn’t limit what we can do on an ebike. If possible, it should assist us in developing our skills and doing new things.Also, I appreciate the reduced motor noise and the absence of motor rattle. The motor noise didn’t bother me that much, it just blended with the sounds from tyres, cables and the chain. But when riding a more silent bike, it just feels more pleasant. I get a sense of relief for every sound that is eliminated. It makes the entire bike feel more solid and well designed.
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