could someone please tell me when and why you use a short cage rear mech and when and why you use a long cage rear mech

i am looking for a rear mech for a Trek EX9 and I am unsure which one i need

i guess i will need the short because they seem to about £10 dearer that the long cage ones!

There's no real need for long cage mechs unless you run a 34T cassette or a 48T chainring.

Short cage (as in Sram Medium cage or Shimano non-shadow GS- NOT Shimano Shadow short, which is really a long) is better and will work in all your gear ratios if you run 22/32/44 chainrings and an 11-32 cassette- i.e., a normal set up.

Short cage mechs shift better, are less likely to break and look nicer.

short cage 1 front ring. (maybe 2 a roadie cassette)
Medium cage 2 front rings..
Long cage 3 front rings…

Though you can use a medium on a triple ring setup if dont ever go big ring, big ring.

What tinsy said. If you run 2×9 and do spring for a medium (why do they cost so much extra?) you can just get whatevers cheapest next time and re-use the medium cage, dead easy to switch. (assuming you didn't trash the cage).

I had a tried Shaddow mech on my hardtail and I couldnt work out why they bothered to have a new design and then I knicked it off my wifes bike for a try and it was lovely, so she got my XTR and I was happy to have the cheaper SLX, Shaddows are really quiet as the mech itself cant contact the chainstay like a normal one… Reccomended if your buying a new one anyhow.

i would if they did them in rapid rise (most under appreciated shimano technology ever)

old style XTR rapid rises are pretty good value on CRC…

As long as you don't cross-chain you can use short cage.

I have xt rapid rise medium cage on all three of my bikes.

bike 1 = 44/34/22 tripple 11-32 cassette
bike 2 = 1×34 single 11-32 cassette
bike 3 = 44/34 double 11-25 cassette

shouldn't ever run big chainring to top sprocket, you can find a ratio the same as that on the middle ring further down the sprocket. Same as small to small, shouldn't go down the cassette too far when on granny chain ring.

Kev

D0NK – Member
i would if they did them in rapid rise (most under appreciated shimano technology ever)

agreed.

have xt rapid rise 'short' on a two chain ring set up and it runs without problems. just make sure the chain is three links longer than it need be incase you let your mate, who is unable to convert pieces of verbal information into practicle advice, have a ride of your bike.