Which Rear Derailleur Do I Get?

[vandeec5]

I have upgraded my shifter from an Sram SX-4 to a Sram X.7 and now I want upgrade the Sram SX-4 Rear Derailleur. I was browsing the internet and found a Sram X.7 Rear Derailleur for a good price but there are two size, Long and Medium and I am not sure which size I need. How do I determined which one I need?

[CalEpic]

If you have 3 chainrings on the front, get the long cage

[dubjay]

If you have a triple ring up front, more than likely you'll need the long version.

[El Gringo]

1 Chainring = Short Cage
2 Chainrings = Med Cage
3 Chainrings = Long Cage.

Remember the purpose of the cage is to regulate chain slack in the different gear combos. Hope that helps.

[CPATCRASH]

What they said.

[vandeec5]

Sweet, Thanks for the fast response Learning something new everyday.

[brett]

1=short, 2=medium, and 3=long is a huge over-simplification. Running a larger cage than is necessary allows you a more sloppy/fuller range of gearing choices without trouble but reduces clearance, increases chain slap, and changes the feel of the shifts. This has been discussed to death on, ahem, another website.

[foofighter]

so if you're running a 2x9 setup w/ a 32/22 chainring you technically can run a short cage and a medium right?

[silverspot]

Originally Posted by foofighter

so if you're running a 2x9 setup w/ a 32/22 chainring you technically can run a short cage and a medium right?

I am running that set up (2x9 32/22) and I use a med cage X-9 AND a Blackspire stinger chain tensioner to boot. No problems ever and I never drop a chain.

[brett]

Originally Posted by foofighter

so if you're running a 2x9 setup w/ a 32/22 chainring you technically can run a short cage and a medium right?

Technically, yes. I've been running 44/32/22 with a medium cage, trading the slack uptake in 22/11-17ish for the benefits of the shorter cage. I don't use the 44t at all so I went to 32/22 last week and will be putting on a short cage.

[BoingBoing]

Capacity is a specification of derailleurs. It's not always listed, but it is the difference between a short, medium, and long cage. If you are running 44/32/22 and 11-34 the derailleur must be able to take up (44-22) + (34-11) half-links of chain. In that case, 45 half-links (teeth) which is the difference between the big-big combo and small-small. Of course, you'd never shift into big-big on purpose, but you don't want stuff to break because of a shifting mistake.

[wheels]

ok, this just answered my other question I had posted...can the mod go delete the post called "the medium cage"

[DirtymikeTDB]

Absolutly, I think I frequent "Other" said website as well!!!

Originally Posted by brett

1=short, 2=medium, and 3=long is a huge over-simplification. Running a larger cage than is necessary allows you a more sloppy/fuller range of gearing choices without trouble but reduces clearance, increases chain slap, and changes the feel of the shifts. This has been discussed to death on, ahem, another website.

Depending on what cassette..... Yes

Originally Posted by foofighter

so if you're running a 2x9 setup w/ a 32/22 chainring you technically can run a short cage and a medium right?

What cassette are you running, I am just curious, also how do you like the stinger???

Originally Posted by silverspot

I am running that set up (2x9 32/22) and I use a med cage X-9 AND a Blackspire stinger chain tensioner to boot. No problems ever and I never drop a chain.

Extremly well said, I always forget the equation, thats why I have it written down!!!

Originally Posted by BoingBoing

Capacity is a specification of derailleurs. It's not always listed, but it is the difference between a short, medium, and long cage. If you are running 44/32/22 and 11-34 the derailleur must be able to take up (44-22) + (34-11) half-links of chain. In that case, 45 half-links (teeth) which is the difference between the big-big combo and small-small. Of course, you'd never shift into big-big on purpose, but you don't want stuff to break because of a shifting mistake.

One thing I want to add, I see ALOT of people coming in wanting a shorter cage derailer so they can shorten there chain lose a gram or two of weight. Just to make it extremly clear, chain length has NOTHING WHATSOEVER to do with your cage length. The proof is right in the "Manual" that comes with a derailer when you buy it, step one in setting up your chain/derailer is putting the chain on the bike, but not through the derailer in your two largest gears, wrap it as tightly as possible, and adding two links from there, then put the chain through the derailer. AGain one more thing added into the mix....... Full suspension.... STep one is to remove the shock, then do the same thing, but with the suspension in a position hat the axle is furthest from the BB during its travel......In other words, wrap the chain, then cycle the suspension and make sure that you find the longest stretch, then add two links!!!!!

[foofighter]

Originally Posted by DirtymikeTDB

What cassette are you running, I am just curious, also how do you like the stinger???

I am running a 34/11 cassette...