Shimano rear mech clutch causing damage?

[aerodiamond]

Here's an interesting issue.

I've been chasing rattles on my '23 Cube reaction hybrid pro. I padded the battery housing, and tightened stuff up. I have it pretty quiet on the bridle ways apart from a rattle when it gets very bumpy. It sounded like chain whipping and stopped when I free wheeled but started again when pedaling...hmm!

The shimano Derailleur has a clutch which is supposed to stop this (it stiffens the chain tensioner in one direction). My thought was that because of this damping the whipping was being g transferred to the sprag clutch in the motor. To check this I turned the Derailleur clutch off and low and behold the noise stopped.

This behaviour could seriously shorten the life of the motor...if I'm correct.

Thoughts??

 

[theremotejuggernaut]

Have you serviced the clutch? They need a bit of maintenance once in a while. Water gets in and the pivot axle rusts.

When that happens, the mech doesn't return as quickly as it should leaving the chain slack at the bottom. Mine was so bad that the mech didn't return af all.

Solution was to remove the pivot axle (took a hammer and a punch to get out) and then soak it in vinegar over night. It was rust free by the morning and worked perfectly once it was greased and reassembled.

Switch the clutch on, manually move the mech forwards and see how quickly it springs back and see if it returns to where it should. I shift it to the 10t in the cassette. The mech should return to take up all the slack. If the chain is still loose then the mech isn't moving enough and needs some love.

 

[aerodiamond]

Thanks for your thoughts.

I did think of that, the mech moves OK but may be a bit slow. I thought the chain may be getting a bit long too, I ride on sandy soils and chain life is in months not years.

I still wonder at the usefulness of the clutch (especially if it is transferring shocks into the motor) in trail riding. I have never yet had a chain come off the front, broken a couple and wrecked a rear but not front. I can see fast downhill racing it might be an issue but muddy bridle ways....

Cheers

Nigel

 

[irie]

After 3,000 miles riding South Downs for 2-1/2 years in all weather my mech was so worn with so much play that it was irreparable. The clutch was so bad that the chain hung like a wet washing line. Claggy mud mixed with chalk and bits of broken flint ground into a paste did its worst.

 

[RustyMTB]

I wonder if the clutch is working as intended but amplifying the backlash present in all Bosch CX motors. Turn the clutch off, lower chain tension reduces & the chainring is subject to less rearward force.

 

[Bones]

If you go on the Shitmano website you can get the PDF of how to service the clutch and set it up.
When mine played up it made the chain jump off the chainring on long bumpy/ grassy decents.
That's when I took the chain guide off because it wasn't easy getting the narrow/wide setup right.
Anyway different subject, but if the clutch is working then you don't need the chain guide on as mines been off now for a couple of years without any issues.

 

[RustyMTB]

Clutches are also adjustable. There are videos out there showing them being set up with tension gauges which is a bit beardy but you can play around with the tension easily enough until it settles down to your satisfaction & as noted above, they do need an occasional service I.e. clean & regrease.

 

[S13]

I always ride with the clutch off. Just works better that way. Better shifting, never have a problem with chain falling off. And that is riding the Alps and Pyrenees.
And as the RustyMTB mentions, you can adjust the clutch. I adjust them so i get a little bit of clutch action in the off position. That is enough to stop the chain from slapping around and still allow for smooth easy shifting.