Trek Allant 8s Random Assist Cutoff

[biker1234]

Hello, I have issues with the Bosch powertrain on my Trek Allant 8s. The assist cutoff on my model Is 28 mph. It worked perfectly for a while but over the last few days I've been struggling to get above 25mph. I noticed the speedometer becomes very erratic around that speed (will display say 29, 22, 25mph within the same second). I'm supposing that since it goes above 28 for a brief moment while I'm in fact going only 25 probably triggers the support withdrawal. Could this just be a speedometer sensor issue?

 

[Stefan Mikes]

This has been already discussed. See this thread:

Trek Allant+8S crank resistance in turbo at top speed

Hello, I bought a Trek Allant+8S a few weeks ago and like it a lot. I've had one issue with it, though, when riding at top speed in turbo. The crank becomes hard to turn and the speedometer jumps wildly from 35kph - 45kph. This doesn't cause the generation of any error codes in the app and the...

electricbikereview.com

Not sure if that was ever resolved. What does the LBS say?

 

[biker1234]

No read that thread. They sent me here!

 

[Alaskan]

This has been already discussed. See this thread:

Trek Allant+8S crank resistance in turbo at top speed

Hello, I bought a Trek Allant+8S a few weeks ago and like it a lot. I've had one issue with it, though, when riding at top speed in turbo. The crank becomes hard to turn and the speedometer jumps wildly from 35kph - 45kph. This doesn't cause the generation of any error codes in the app and the...

electricbikereview.com

Not sure if that was ever resolved. What does the LBS say?

Stefan, I suggested the OP take the discussion into the Bosch sub forum as it is more likely to get some help from the Bosch team.

Of course, as this is a new bike, it is best the bike be taken in for warranty service, to the bike shop where it was purchased .

 

[Stephen - Bosch Team]

Hello, I have issues with the Bosch powertrain on my Trek Allant 8s. The assist cutoff on my model Is 28 mph. It worked perfectly for a while but over the last few days I've been struggling to get above 25mph. I noticed the speedometer becomes very erratic around that speed (will display say 29, 22, 25mph within the same second). I'm supposing that since it goes above 28 for a brief moment while I'm in fact going only 25 probably triggers the support withdrawal. Could this just be a speedometer sensor issue?

Ahh, thanks for the detail! You seem to have the same hunch as I. My gut says your speed sensor **may** be failing. On the Allants, this sensor is actually a Trek part. I would take it into your local Bosch/Trek dealer to have them troubleshoot the sensor/magnet. It should be a quick fix if it is that.

 

[Alaskan]

@Stephen - Bosch Team and @biker1234
I have an Allant 9.9S. The magnet is in a fixed position, built into the brake rotor. The speed sensor is just behind the brake caliper
and is quite small.
https://bike.shimano.com/en-US/product/component/e-bike-e5000-series/RT-EM600.html
The magnet is between two bolt holes almost at 12 o'clock in the image below. I would think the sensor is more suspect than the magnet.
This is definitely not standard Bosch stuff. I strongly suspect that this is a Trek proprietary sensor that you will have to bring it into the Trek shop to fix.