Can anyone tell me what the differences between the different length rear mechs are and why you’d choose a particular style? Do different bikes/ setups need different lengths?

Thanks

Andy

the longer the mech the bigger the range of gears you can accommodate.

so for a triple mtb set up you need a long cage

for a double mtb or a triple road set you need medium

for a standard double road set you need a short

this is for optimum performance, a shorter mech can be forced to operate over a bigger range to help prevent chain slap etc but it will wear out/snap quicker

Many thanks

Andy

I run a triple and an 11-34 cassette on my full suss.
I’ve had no problems running a medium cage X9. It does have some play in the bushes now but it is 3 years old (still shifts without a second thought). Pretty bashed up too now so feel I’ve had my money’s worth out of it. I went for the medium to increase clearance/reduce chain slap. I don’t cross my gears so never force it over a bigger range anyway. But I did make sure my chain was long enough so that every gear worked just in case. So lack of range has never been an issue but the pros have been welcome.

I run a medium cage X0 mech with a triple chainset and 11-34 too, with no problems.

Should have mentioned the increased chain tension doesn’t just reduce slap it helps to keep the chain on. I found the chain droped too often in my prefered gear for trail centre descents, but after swapping to medium cage I don’t recall an issue.

Replaced my X7 rear mech with a long cage X9 on a triple with 11-32 as I thought/assumed that whas what was on the bike. X9 was longer so I guess the original was medium and worked fine with all sorts of accidental small-small and large-large incidents (usually at night).
Does a full suss bike with chain growth make a difference? Mine is a hardtail.

I’ve got a SRAM medium cage mech with an 11-34t rear and triple up front on my FS. Never had a single shifting isuue that I can recall

You want to read THIS ARTICLEabout gear cage length.

It’s about having a usable range of gears without knackering your chain.

Good article. Basically says for the gear range you actually use, a long cage is unnecessary. Who would run 22T to 11T on a triple anyway? So go for a medium cage for all the benefits it gives. Quote from article:

Benefits of a shorter cage length?
– snappier shifts
– better chain tension
– less chain slap / greatly decreased drivetrain noise (!)
– better obstruction clearance / improved spoke clearance.
– slight weight loss — but you gotta be a real weight weenie to appreciate this one