Bosch Gen 4 CX binding, no error code.

[veearrsix]

I was out on my Cube 140TM this morning, just refreshed the drivetrain as my cassette had given up after 1400miles. All was well until i wanted to change gear going up a slight gradient.

As I changed gear it felt like my chain/derailleur had become jammed, I changed back down and pedalled to a flat spot. Checked everything over, nothing wrong. No catastrophic failures, not even a quiet ping from anywhere.

What appears to be happening is that, when I have zero assistance the crank arms feel like they are binding (when turning in a clockwise direction), pedalling backwards does not bind at all. It was hard to spot as when under load and the motor is assisting, the cranks feel like normal, but every now and again I would get what felt like a burst of extra boost, but that was the crank not binding for a split second. So, this isn't me hitting the limit and feeling the weight of the bike, I know what that feels like, plus I can replicate the binding clockwise cranks by going down a gradient in a spinny gear (where you wouldn't expect any assistance) and trying to pedal, the cranks don't want to turn, its possible to overcome the binding but it is definitely there.

I have no error codes, never been jet-washed, and it wasn't caked in mud, not weird sounds from any bearings, it all looks fine. Any ideas, anyone else experienced this?

 

[Shark58]

Did you try removing the chain and then turn the cranks? If you can still notice the binding it comes from the motor. If not it comes from the cassette or chain.

 

[veearrsix]

It was a false alarm with the motor, turns out the cassette had managed to undo itself (xd driver) and was binding up against the derailleur hanger.

It never even crossed my mind that this would even be possible as it has never happened to me before with decades of using shimano cassettes, but you live and learn. I know need to figure out what the cause was, as I tightened it back on, only for it to undo again today. The new cassette (2 rides) is now toast, as the driver has gouged out the cassette where it would normally engage with it. The threads on the driver don't look great, so maybe there wasn't enough thread and the cassette "popped" off. Or it could well have been user error when I fitted the new cassette. Even so I have no idea how it would have backed off the thread... Weird!

 

[irie]

It was a false alarm with the motor, turns out the cassette had managed to undo itself (xd driver) and was binding up against the derailleur hanger.

It never even crossed my mind that this would even be possible as it has never happened to me before with decades of using shimano cassettes, but you live and learn. I know need to figure out what the cause was, as I tightened it back on, only for it to undo again today. The new cassette (2 rides) is now toast, as the driver has gouged out the cassette where it would normally engage with it. The threads on the driver don't look great, so maybe there wasn't enough thread and the cassette "popped" off. Or it could well have been user error when I fitted the new cassette. Even so I have no idea how it would have backed off the thread... Weird!

I've put cassettes on wrong but fortunately realised when I had a spare spacer left in my hand, and another time didn't line up the smallest 3 sprockets correctly!

 

[Mikerb]

your problem is/was with the XD freehub.....presumably pawls not disengaging when you freewheel.

 

[veearrsix]

your problem is/was with the XD freehub.....presumably pawls not disengaging when you freewheel.

Thats really interesting, is that something thats happened to yourself? If so, was there anything obviously wrong with the free-hub body? Mine feels absolutely fine and it wasn't caked in grease or anything.

 

[Mikerb]

Thats really interesting, is that something thats happened to yourself? If so, was there anything obviously wrong with the free-hub body? Mine feels absolutely fine and it wasn't caked in grease or anything.

No...my bikes use DTSwiss ratchet XD feehubs.
I was surmising that for the cassette to unscrew from the freehub......its a standard thread......the freehub would need to turn with the wheel whilst the cassette is not turning (ie freewheeling). That could be momentary but enough to start loosening it. So either the pawls are not disengaging or the freehub bearings are seized/ partially seized.

 

[veearrsix]

Certainly makes sense, the freehub looks fine, but it is really quiet, so I don't know if I'd be able to tell if it was stuck.

I've managed to rescue the cassette, and double/triple checked I've fitted it correct and to the correct torque, so I'll try and listen out on the next ride.

So tempted to swap over to microspline!