As above what effects the length of the rear cage you can use on a bike? I see my D/H mates using short mechs i guess because they have small cassettes and only one front ring. Whats the correct rule to determine what cage length??

rear mechs generally have a capacity measured in teeth numbers, can’t remember off the top of my head how it works out, but isgoverned by the relationship between small-small and big-big combinations. A long cage mech has a higher capacity so can deal with bigger differences between cassette and chainring sizes, but shorter mechs can be used(with a shorter chain)without running into slack chain problems as long as you don’t use big-big combinations.

If you never cross-chain you can use a short mech with a standard triple plus wide range cassette. If, however, you sometimes stray into those awkward gear combinations (biggest and biggest or smallest and smallest front & rear) then you need the long cage.

I like short cage – set up with a shorter chain = less chain slap. Looks better too!

I’m with glenp

I use a short mech, prity much the same setup too, but if you have your chain to the right lenth to can get all the gears, but it does take some settgin up with getting the correct chain lenth.

Nezbo.

medium cage just about covers all bases? short cage for a single/double