shouldo i be worried?

[JamesW]

New cube bike, Bosch performance line motor, 200 miles so far. Cycling to work this morning came to a stop ( for traffic lights) on the last hill before work and dropped down 2 gears from top gear. I was in turbo mode as I needed to get to work really fast and the extra booist away from the lights/junctions always helps if this is the case. Lights changed and I put my right foot down hard to start up the hill and the rear wheel locked ( which really hurt!) Had to edge to the side of the road and walked it up hand over the crossing. Checked the derailleur for the expected jammed chain and nothing. Turned electric off to see if I could cycle unpowered. And succeeded. Turned electrics back on and bike is fine again.

So what happened to my bike that nearly pulled my hamstring?
Did a clutch in the motor get jammed and free itself? Did I push too hard? Do I need to worry about this happening again? Has anyone else experienced this?

Help

James

 

[Hatters]

On 3 occasions over the last 2 years I have lost engagement between the crank & chain ring on my Bosch Gepida. The crank just spins in either direction whether power is switched on or off yet the motor will still operate on the walk mode switch. The only remedy is a couple of sharp taps on the crank with a stone or heavyish implement. Is there a sprag type clutch in the motor which is hanging up? Can it be accessed & cleaned or greased? Could a pawl break off & seize system up ? Anyone stripped a Bosch motor down?

 

[Emo Rider]

Had the bike already physically downshifted and was in the lower gears or did you downshift while stopped and then proceeded?

 

[Hatters]

Who you asking Emo?

 

[Emo Rider]

Who you asking Emo?

Asking the O.P. If he tried to pedal away without the chain engaged in the selected gear, that might have been why it jammed. The thin chain and narrow spacing of the 10spd cassette are not as accommodating to that type of use as are other setups. Still, ideally, you should always be in gear before proceeding.

 

[Hatters]

Fully agree, particularly if you are in turbo mode. Have you any knowledge on my Bosch query?

 

[Emo Rider]

On 3 occasions over the last 2 years I have lost engagement between the crank & chain ring on my Bosch Gepida. The crank just spins in either direction whether power is switched on or off yet the motor will still operate on the walk mode switch. The only remedy is a couple of sharp taps on the crank with a stone or heavyish implement. Is there a sprag type clutch in the motor which is hanging up? Can it be accessed & cleaned or greased? Could a pawl break off & seize system up ? Anyone stripped a Bosch motor down?

I have not heard of this problem and never stripped a Bosch down as any problems resulted in sending it back. Perhaps starting a new thread of your own with this query could result in some help from the knowledgeable bunch here.

 

[JamesW]

I had already effected and competed the gear change before coming to a stop for the lights.

 

[Hatters]

Thanks Emo

 

[Emo Rider]

I had already effected and competed the gear change before coming to a stop for the lights.

Sadly I have no answers to this. Perhaps contacting Bosch directly could help. I have not read about any similar problems but a search of previous threads may help as well.

 

[Deleted member 4366]

I reckon it was a case of chain suck, where the chain sticks to the small drive sprocket and wraps round it until it meets the chain on the lower run and jams the sprocket. The people that ride in the mud get it a lot. It's a real problem with the small sorocket on your type of Bosch. It won't happen on the crank motors with big chainrings like the old style Bosch.

 

[RobF]

I reckon it was a case of chain suck, where the chain sticks to the small drive sprocket and wraps round it until it meets the chain on the lower run and jams the sprocket. The people that ride in the mud get it a lot. It's a real problem with the small sorocket on your type of Bosch. It won't happen on the crank motors with big chainrings like the old style Bosch.

Very likely, particularly accelerating hard in turbo which means the teeth of the sprocket are harder against the rollers of the chain, making it harder for the chain to release from the sprocket.

There's also less time for that to happen than when accelerating gently.

I've ridden with - not against - a couple of roadies.

Pulling away from rest is one of the few opportunities to gain a few metres on them.

But I would question if accelerating hard would have any meaningful impact on the OP's journey to work time.

 

[EddiePJ]

As has already been said...If the chain had been muddy or very greasy, then I'd be thinking chain suck. It would have released itself the moment that your foot was off the pedal, so you wouldn't have seen it.
If the condition of the chain is fine and clean, is the front sprocket hooked and worn. If it is, then that won't help things.
If your rear derailleur has a clutch, engage it, as that goes a long way to help prevent it.

 

[LEBC Tom]

Seen this a few times on the Bosch with the granny cog, chain suck. Keep the chain mud and gunk free.

 

[JamesW]

Don't think it was chain suck. Cleaned the bike again last weekend (it's a weekly thing for me as riding on roads I don't get quite as muddy as EddiePJ) degreased chain and relubed with wet lube only 30 miles ago. Haven't been anywhere muddy. Bike has only just topped 220 miles total today and still looks like its just done 1 short dusty ride home from the shop where I went down a dirt track this evening.
Will have to ask about the clutch thing on the derailleur tomorrow when I pop into the bike shop again to tell them I've found the source of a rattle I'd been associating with the front brake - loose spoke not picked up at first service today.

 

[EddiePJ]

Giving more thought, and the fact the bike is new and immaculate.Check that you don't have a tight link in the chain.

 

[KTM Bike Industries UK]

Sadly I have no answers to this. Perhaps contacting Bosch directly could help. I have not read about any similar problems but a search of previous threads may help as well.

Bosch don't deal with the public direct I'm afraid, your first port of call with questions / issues like this is always the bike shop you bought the bike from. But as you've added, the internet can often provide a solution or narrow down the issues.

 

[JamesW]

Giving more thought, and the fact the bike is new and immaculate.Check that you don't have a tight link in the chain.

OK I will have to work out how to do that - ill ask at the bike shop this pm. Thanks Eddie