Shimano EP8 (DU-EP800) – abrupt assist cut-off after service

[AlexBentley]

Hi everyone,

I have a Canyon e-MTB with a Shimano EP8 (DU-EP800) motor. I bought it second-hand, and after some time I started hearing a clicking/cracking noise from the motor when pedaling.

I took it to a workshop — they serviced the motor, cleaned it, and replaced the grease.

After the service, a strange new issue appeared:
The pedal assist now cuts off immediately at the slightest loss of pedal torque. Even a small unevenness in cadence or a tiny bit of slack in the crank rotation causes the assist to stop instantly. When I pedal continuously, the assist may cut out and re-engage repeatedly.

Before the repair, the motor behaved as expected — when I stopped pedaling, assist would continue for about one second before disengaging. Now it shuts off abruptly with no delay at all.

• No error codes are shown on the display or in the E-Tube app.
• Local workshops haven’t seen this before.
• I couldn’t find similar reports online.

Has anyone experienced something like this with the EP8? Could this be related to a torque sensor, firmware setting, or something that might have been affected during the service?

Thanks for any advice!

 

[Amber Valley Guy]

My EP8 has never given assistance when I stop peddling, which is annoying when trying to clear obstacles uphill, but it does keep going when you reduce pedal pressure, just less (torque sensing) when under the limit. Are you hitting the limiter? And do you have the firmware with the hard limiter (25kph/15.5mph) or the later firmware with the soft limiter (26kph/16mph)? The later one being much better.

 

[AlexBentley]

Hi! Thanks for your reply! The problem is that when accelerating, the motor can cut out and turn back on for a second. This happens at the slightest loss of torque while pedaling. If you shift gears with perfect timing, this problem rarely occurs. But riding like that is inconvenient – you have to shift too many gears even on flat roads to accelerate. It didn’t used to happen before. My speed limit is set to 25 km/h.

 

[Amber Valley Guy]

Sounds perfectly normal for an EP8, they're designed to mimic an analogue bike. But saying that they shouldn't cut out if below the speed limiter. Have you updated the software since the service? Maybe they reset it back to the initial firmware (which was buggy)?

 

[AlexBentley]

Sounds perfectly normal for an EP8, they're designed to mimic an analogue bike. But saying that they shouldn't cut out if below the speed limiter. Have you updated the software since the service? Maybe they reset it back to the initial firmware (which was buggy)?

Thank you for your reply! I wouldn’t have paid much attention to the motor’s behavior, but this didn’t occur before the repair. The firmware hasn’t been changed, and it hasn’t been connected to any programs. It’s truly a very unusual situation.

 

[Amber Valley Guy]

I'd try updating the all the firmware, via the app and see what happens?

 

[AlexBentley]

I'd try updating the all the firmware, via the app and see what happens?

Thanks! I’m planning to update, but the stories about bikes getting “bricked” during a Bluetooth update are a bit scary

 

[dezzracer]

What does “getting bricked” mean?

 

[Amber Valley Guy]

What does “getting bricked” mean?

Breaking something (usually whilst trying to repair it) whether physically or via firmware/software updates that go wrong, perpetually hang, no longer boot etc etc.

 

[AlexBentley]

What does “getting bricked” mean?

Specifically with Shimano motors, firmware updates are done either through a special PCE cable, which dealers have or can be purchased for around €300, or via the E-Tube app using Bluetooth. When using Bluetooth, however, there is a high chance that the update will be interrupted during the process, and the bike will stop responding to any actions. In that case, it’s impossible to resume the update, and you’ll need to go to a dealer and connect it to a PC.