Gen 4 klunk when you start pedaling? if i am on a small cog and coast and then statrt pedaling

[Third-Reef]

My bike, 2021 TREK Rail 9.7 seems to have developed sort of a clunk or thud. If i am on a small cog and start to pedal it feels like there is a slight delay and then thud as the power starts to apply, coast and then start pedaling and it does it again. Anybody else have this. wondering it it has been there all along and i am just now noticing it. the bike has about 125 Mi. of semi hard riding on it.

 

[Gyre]

There's some kind of "freewheel"-like clutch in the Bosch Gen 4 motor - when the motor comes on it takes up a tiny bit of "slack" (for lack of a better word) and then you feel it engage. The engagement is subtle, so I definitely wouldn't call it a "clunk" or "thud" though. If that's what you're experiencing I'd say you have a warranty situation.

 

[Third-Reef]

i think you are referring to the sprag clutch. I am going to take it back to the LBS where i purchased it and have them ride it. It may be normal, but as an engineer I am cursed with the "why does that happen?" thought process all the time. If it stayed as is for the rest of time it would be OK.

 

[Gyre]

Not arguing over the clutch type, but if it's a sprag clutch it's interesting that it makes a distinct ratcheting sound when you backpedal. Anyhow, sounds like a good idea to take it back to the LBS. Maybe they have another Gen 4 bike there you can test ride for comparison.

 

[Dave_h34]

My bike, 2021 TREK Rail 9.7 seems to have developed sort of a clunk or thud. If i am on a small cog and start to pedal it feels like there is a slight delay and then thud as the power starts to apply, coast and then start pedaling and it does it again. Anybody else have this. wondering it it has been there all along and i am just now noticing it. the bike has about 125 Mi. of semi hard riding on it.

I'd say yes, 2021 Trek Rail 7. Noticed it on first or second ride, happens very sporadically so convinced myself it wasn't a problem. Interested to see how you get on. ?

 

[markloch]

i think you are referring to the sprag clutch. I am going to take it back to the LBS where i purchased it and have them ride it. It may be normal, but as an engineer I am cursed with the "why does that happen?" thought process all the time. If it stayed as is for the rest of time it would be OK.

Same here - about 150 miles on a Rail and noticing the same, most notably in emtb-lite mode (just had trek shop swap emtb-lite to replace tour; I don’t think I noticed it prior to the swap, but I was rarely out of emtb before the swap, now I go to lite fairly often).

Let us know how it goes At the LBS.

 

[aimage]

I have a new Rail 9 with the exact same issue. Only done 50km and its noticeable in any mode with the motor engaged. As in works normally when it's off. Advise from Bosch is run it in to 200km then they will look at it. Anyone been down this path and found a source/solution?