Grey lever on Deore derailleur

[mark a.]

Can anyone tell me what this lever does on the Deore 10-speed derailleur?



It moves up (in the direction of the arrow shown) but it's not obvious that it does anything.

I've only had the bike for over a year and I've only just noticed it. Sincere apologies for the mech not being spotlessly clean

[simonineaston]

If its the same as on my Zee mech., it's the 'clutch' - it's supposed to increase friction to the rotation of the cage, the idea being to control excessive movement of the chain.

[ElCani]

It's the clutch for the derailleur. It keeps the lower chain run taught to reduce chainslap and the chances of the chain coming off the front ring(s) when you go over bumpy ground. Causes a tiny amount of energy loss, but still worth leaving in the ON position at all times, IMHO.

[mark a.]

Ah, so it's a clutch mechanism. Great, I just never knew I had one.

Which is the on position?

[thelawnet]

On is up, that is off.

Turning it on and it will be quite obvious if you bounce the rear wheel on the ground as there will be much less chain slap.

Also removal of the wheel will be difficult with it on.

Not all Deore 10 speed derailleurs have a clutch, fwiw.

[simonineaston]

Well, I wouldn't have thought such a device provides much benefit to a road cyclist, but hey - what do I know... ? Cycling Weekly discussed this a couple of years ago.

[mark a.]

Thank you. I'll flip it back on. I was struggling to get the wheel back on after fixing a puncture (some lovely person scattered thumb tacks over the cycle path this morning) so perhaps I'd had the clutch on.

The bike is a Tern GSD with a long chain (and a chain guide pulley halfway along the top run) and small wheels, so I imagine the clutch is actively useful with all that chain flapping around.

[mark a.]

Well, it's certainly quieter. I'm not sure the clutch has ever been on until now. Thanks everyone.