[Closed] long or medium cage rear derailleur ???

You will need a long cage. It is really that simple, long cage for a triple, medium cage for a double and short cage for a single ring. You can use long for a double etc but the changes won't be as precise. I'm sure someone will copy and paste the wonderful equation to do it exactly but you will have the same answer.

I'm not convinced it's as simple as double = medium anymore. In 9-speed days double usually meant taking the big ring off and cassettes did not have such big ranges therefore it was fine.

A 10-speed double setup using a 11-36 cassette and 38/26 rings is outside the stated chain capacity for a medium cage Shimano mech. Whether that means it won't work I don't have practical experience of. My feeling thought that with a double where you will actually want to be able to use the big/big combo a long cage is needed. Also with Shadow + clutch mechs I'd be less inclined to go outside of the manufactures stated capacity.

That's all based on my theory rather than actually trying it so I'm sure some one will come along in a mo and say 38/26 + 11-36 with a medium cage clutch mech is fine!

I looked into this, and this is my limited understanding.

I use all the cassette when using the middle ring,
Top three gears only when using the big ring and only the lowest three gears when using the granny.

Using a long cage, gearchanges are not as quick and precise as they would be with the med but if I did through lack of concentration or accidental shifting find myself using all the cassette in all of the rings it would not be ideal, noisier and putting more wear on the drive train, but over a short period of time no real damage done.

With a med cage and 3 rings if i shifted correctly using only the ideal ring cassette combos you should be ok but if you accidentally found yourself in the granny ring/high gear combos for instance the deraileur would not have the lengh to take the required amount of slack out of the chain and it could drop off.

I think.

Very good explanation here - http://forums.mtbr.com/drivetrain-shifters-derailleurs-cranks/when-use-long-cage-vs-short-cage-derailleur-205890.html

In common with lots of people I've run a medium cage with a triple for many years with no issues. The only potential downside is that not all gears are available as you can't run big-big and small-small can be an issue too. This is all on 9-speed but I doubt that running 10-speed would be significantly different.

muffsthemonkeyhanger - Member
You will need a long cage. It is really that simple, long cage for a triple, medium cage for a double and short cage for a single ring. You can use long for a double etc but the changes won't be as precise. I'm sure someone will copy and paste the wonderful equation to do it exactly but you will have the same answer.

Not completely true. My Pitch came with a medium fitted and a triple. No gears were unavailable, but then ratios of small small or big big aren't advisable anyways.

I use a medium cage for a triple 22-32-44/11-32 set up. It does limit the available sprockets when in granny ring and big ring though - ie. pretty much what Chip says ^^ up there ^^ I can only use the top 3 in granny ring, possibly 4 or the chain slackens off too much and on the big ring I don't go near the top four or I'll stretch the mech too far. It works for my riding, I use a rapid rise mech too.

That's all based on my theory rather than actually trying it so I'm sure some one will come along in a mo and say 38/26 + 11-36 with a medium cage clutch mech is fine!

And here I am ... 😀

Yep 38/24 with 11/36 and a medium cage XT RD. And I use [i]all[/i] my gears!

Running 11/32 out back and 24 / 36 / 46 on a medium cage with no issues at all.
Depends how much attention you pay to what gear you're in.
If you ever end up in big big / small small then probably not a good idea.
If you have a bit of mechanical sympathy you'll be fine.

That's all based on my theory rather than actually trying it so I'm sure some one will come along in a mo and say 38/26 + 11-36 with a medium cage clutch mech is fine!

And here I am ...

Yep 38/24 with 11/36 and a medium cage XT RD. And I use all my gears!

Balls! Out if interest is that on a full-suss.? The changing chain length through the rear suspension travel was an additional concern I had.

Balls! Out if interest is that on a full-suss.? The changing chain length through the rear suspension travel was an additional concern I had.

Yes its on an Anthem 29er, so relatively short travel (100mm) but full suspension nonetheless.

I'm gonna be converting my other bike (a Trance with 125mm travel) to 2x10 over the weekend, and I'm going to be using 22/36 on the front plus 11/36 on the rear with a medium cage SLX Shadow + RD. I'll let you know if that [s]explodes into a milion pieces[/s] [i]breaks the chain[/i] (edited out of respect for our American friends 😳 ) once I've had a chance to try it...

As per usual these threads get out of hand.
Basically mate try the long cage mech you already have. If you are missing gears you need or would like to have then sell it and get a medium.

If you didn't have the long cage, I'm assuming you did as you have a triple. And you have a choice it's medium cage, end of

How would you be "missing" gears using a long cage?

Thanks for all the advice.

I never use the large front chainring
but often use the granny with the 2nd largest rear cog (lots of nasty long hills STEEP hills).
So sounds like I am best to go for a long cage to make the most of the low gears.
I can put up with less crisp gear changing if it means I have better access to the lowest few gears.

A medium cage mech will be fine, just dont put in the extremes (big big / small small)
Either mech will work fine. If you've got a long cage one use that, if you've got a med cage one use that.

Promised to report back on whether my latest build works with a medium cage...

Giant Trance 26" with 5" suspension travel, 2x10 SLX drivetrain, 11/36 cassette, 22/36 chainrings (so a 39T difference), M675 SLX shadow+ medium cage RD (which Shimano say has 35T capacity).

Works great - but I'll admit it's close, very close... 😀

I'll admit to being massively thick here but isn't chain length also a factor?

I'll admit to being massively thick here but isn't chain length also a factor?

Well yes of course you have to size the chain correctly, and the closer you get to the capacity of the cage then the more critical it becomes to get the chain length exactly right.

Suspension travel and design is another important factor (which is why I mentioned what mine was above) because it will cause 'chain growth'.