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I've got a 1x10 set up. Sometimes I have a problem with the chain falling off at the front. I've been reading that a clutch mech will help to prevent this.

My mech is Deore long cage without clutch. What is the dis/advantages of a clutch mech vs a chain tensioner / chain guide?

Bike is 2006 Specialized Rockhopper Pro. Chain is correct for chainring. Its not worn, nor the chainring etc. Chain line looks fine, but maybe this could be tweaked slightly.

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    Before getting into the ins and outs of clutches etc, are you aware that most bikes with this setup don't need anything to stop the chain falling off? This indicates that the bike has pre-existing problems that you should correct, if possible.
    – PeteH
    Commented Jul 17, 2016 at 15:24
  • The bike has no problems. It only happens about once or twice per ride over very uneven terrain with particularly sudden direction changes etc. Commented Jul 17, 2016 at 15:26
  • @PeteH Is that really true? I thought chain dropping is a common problem for single-ring MTB setups; that's the whole reason that narrow-wide rings exist, after all. Commented Jul 18, 2016 at 10:41
  • @WillVousden unfortunately I don't know a great deal about clutch derailleurs, but certainly the chain dropping off that frequently made me guess that something else is coming into play (e.g. chain line), after all if you get a narrow-wide bike out of the factory, you don't expect this to happen. But mattnz's answer says this more informatively than I do.
    – PeteH
    Commented Jul 18, 2016 at 11:05
  • It is more likely to happen than with a triple ring set up. because of the f derailleur and two other rings that the chain can land on. Commented Jul 22, 2016 at 19:53

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"Once or twice per ride" - that is way beyond what I would consider only. That would destroy my confidence in the bike and ruin any enjoyment I got from riding.

A new dérailleur might help, but might not. There are other things I would look into first, PeteH in his comment is correct - the number of drops you are suffering is an indication something is very 'not right'. If a new Clutch dérailleur appears to fix it, its is probably just masking the problem. Chain guides hide all sorts of evils, but are a practical option that will work.

Shimano 1x10 was not an out of the box set up, what was the original setup and what has been replaced with what?

What chain ring are you running, is it damaged at all?. If you are running a normal 3x or 2x chain ring, a chain-ring for a single will help, especially a narrow/wide.

What is the chain line like. When you drop the chain, is it in normally in a particular range of gears

Along the same lines - is the chain length correct. As its a long cage dérailleur you have a lot of scope for too much chain.

How worn is the dérailleur - its more likely a new one will help of its been used a lot.

With so many unanswered questions, I would consider a new dérailleur if the other is well used, but would focus on chain (how old, does it need replacing and length) chain line and chain ring first. If these are all good (and the chain ring is dedicated for single, ideally narrow/wide), the choice is a new dérailleur which might work, a a chain guide while will work.

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  • Derailleur is deore - recently new, shimano Zee cranks and ring - almost new, 10 speed chain. Might be a chainline issue. Thanks for the help. Commented Jul 22, 2016 at 19:52
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A clutch derailleur does a better job of tensioning the bottom portion of the chain. This keeps one side of your chain more aligned, and it slaps around less when you ride over uneven terrain. People like clutch derailleurs because they also reduce the noise of your bike.

The problem is, this added tension doesn't help the top part of your chain, and that's usually where the chain falls off. Typically when a chain falls off, it bounces off of a tooth or two at the front chainring (the top portion of the chain). Then, when you pedal (moving the top part of the chain forward towards the chainring) that levers the chain off the teeth completely.

A clutch derailleur is not enough security for your chain if you are riding off-road. It only solves half the problem. This is why SRAM and Shimano make front chainrings specially designed to hold a chain more securely in a one-by setup. Some riders find these narrow-wide chainrings and clutch derailleur to be enough. In really aggressive terrain or depending on your bike (full suspension bikes cause more movement in a chain) you may also want a chainguide.

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