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· Registered
121 Posts
Discussion Starter · #1 ·
I have a conundrum here. I'm working on building up a bike and I want to get a short cage RD so that it stays far away from the logs and granite boulders that tend to eat said component. This is a big issue where I ride, and I really want to make a short cage work.

(forgive me for the dissertation, but this will take a little explaining) :nonod:

Here's the dilemma:

after some research, I found that (SRAM) Short cage RDs hold about 30T of chain, Med. hold about 37T. Now I want to use a 11-34 cassette, w/ a 22-32-bash up front. BUT I would like to be able to slap on a 44t ring for commuting occasionally.
Now, what I found was that to find out what length RD you need, you use the following formula:

(largest chainring - smallest chainring) + (largest cog - smallest cog)

so in my case it would be (32 - 22) + ( 34 - 11) = 10 + 23 = 33
and for commuting (44 - 22) + ( 34 - 11) = 22 + 23 + 45

now to the crux of the matter. would using a chain tensioner, the BS Stinger in particular, help to take up the extra few T of slack when the chain is in the granny gear and is working its way toward the 11t cog? and conversely, would it keep the chain too tight to allow it to smoothly move toward the 34t cog, while the front is in the middle (now big) ring ? I'm also well aware that ANY cross chaining is out of the question with a setup like this.

as for a commuting setup, I know that there would be some impossible combos with a 44t big ring, basically it would preclude the whole 34t end of the cassette. what I was thinking was: remove chain from Stinger, leaving Stinger mounted, swap bash for chainring, re-index FD for big ring, tape note on handle bars reading: DUMBASS! DON'T SHIFT PAST 5 !!! ( or something to that effect), ride.
My ( probably faulty) logic is that while on the middle ring, the higher gears would be a little sloppy, but being on flat ground, that's not too bad. By the time you need the big ring, you're already going fast enough that you should only need the cogs on the 11t end of the cassette.

[ Don's NOMEX suit] what do you guys think?

· Just a flesh wound
2,367 Posts
So many things..

I use a XTR mid cage on my Prophet after trashing two long cages. It has 33T capacity. Set it up originally for 3 X 9. Big big +1 or 2. Don't use Granny with any of the smaller cogs, middle is suspect in 7 (slap), no good in 8 or 9 (sloppy chain). But this is just a chain etiquette issue, shift smart and keep your chainline as straight as you can.

I switched to 2 X 9 when I mangled the big chain ring. It's a 43 tooth log gripping bash guard now. Shortened the chain to fit the new mid big and it is great with the short cage (Shimano version).

Commuting is a different story. I suppose you could use a chain tensioner and remove it when you install the big chainring. Or you could use two quicklinks at the ends of a length of chain that you could insert into the shorter 2 X 9 chain length.

Good luck!
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