rear deraileurs

Anonymous

Just a quick one, whats the purpose of short medium or long cage rear mechs?, i'm going to buy 2 new mechs (both bottom normal instead of the top normal ones i have) and dont know whether to get short medium or long.

anto164

short, is normally used if you have a single ring, medium for dual and long for a triple.

BUT.. it depends on what ratio on the rear cassette you have. sometimes if you have a large range of gears on the back, and a single on the front, you need a medium cage, to keep correct chain tension all the way through the gears.

Really, though, on a FS, you dont normally run short cage, as the short cage tends not to give enough tension on teh chain all the way through the travel in all gears, or it may give too much tension, snapping the mech.

i think that makes sense...

Andy B

A basic rule is:

long cage with triple chainrings

Med cage with 2 chainrings

short cage with a single chainring.

this can vary depending on the cassette you're using, a ;normal 32(or34)/11 cassette will follow that rule, but a roadie cassette may need a shorter cage.

Edit: Bugger too slow!

TomR

As above, but you could also run a roady mech and cassette if you want to keep things tight, although obviously compromising on gear ranges.

supersonic

Look up mech 'capacity'

jayson

I have a triple chainset with an 11-32 cassette and i run a medium cage mech with absolutely no problems at all. Aslong as u dont run the 2 extreme crossover gears u can usually get away with it.

On my big ring i never go more than4 gogs up the block so the rear mech doesnt have to stretch and the changes are super quick and smooth with less chain and cage trailing.