[Swine]

So what would you do here...

So I am building 2 bikes, a long travel all mountain bike and my old zaskar. I have a new set of 2011 X9 shifters and short cage rear der, and some 2005/06 XTR shifters with a med cage XT rear der well used.

My original thought was to run the new X9 group on the AM bike, since it will be ridden the most and a new drivetrain would be most appreciated. But the fact that its a short rear cage has me worried about breaking stuff. Are these unfounded concerns?

 

[Pslide]

Depends on your front chain ring setup. If you are running a triple, I would not run a short cage. Two ring setup I would think would be fine with short cage though. Just my opinion.

 

[Swine]

Ahh good point, the AM bike is going to be a dual front ring, obviously the zaskar is going to be a triple.

 

[slyfink]

I run a dual-ring front (32t-28t), and a 34-11 cogset in the rear of my 2005 Enduro (150mm travel I think). I run a short cage saint derailleur. I have it set up so that in the big-big combo the derailleur is quite stretched, but not too much. The only problem I (would) have is if I ever were to go small-small (11r-28f). In that scenario, the short cage derailleur can't take up enough chain and it goes all slack. But in three seasons of running this setup, and have never had that problem.

I'd say your biggest issue is that you're running a SRAM product... not the length of the derailleur

 

[Dogboy]

Short cage rear derailleur with anything other than a single chainring is a bad idea. It comes down to capacity which is an easy calculation, but you will most likely be outside of what the derailleur can handle.

 

[syadasti]

I'd say your biggest issue is that you're running a SRAM product... not the length of the derailleur

Actually its the opposite, SRAM typically has greater capacity than Shimano does. In medium cage its 4-6T greater than Shimano (depending on model).

 

[scottbrixie]

Im running the X9 with the Hammerschidt and 10 speed rear cassette on my Butcher....no problems at all. Oh and I believe I have a medium cage

 

[Pslide]

I run a dual-ring front (32t-28t), and a 34-11 cogset in the rear of my 2005 Enduro (150mm travel I think).

That's an odd setup...why the 32T - 28T front?

 

[buildyourown]

Cage length is determined by gear spread, and nothing else. If you are running a single ring, short cage. Double, medium. Triple, long.
Sometimes you can get away with a short cage with a double and a tighter cassette, but what's the point

 

[marshalolson]

just make sure the derailleur can accommodate the gearing. its super easy to figure out.

(big.chainring - little.cassette) + (big.cassette - little.chainring ) = ???

Specs for SRAM Short Cage 9spd
Maximum capacity = 30T
Mininum sprocket = 11T
Maximum sprocket = 34T

so, hypothetically, if you had a 22/32 and 11-32

(32-11)+(32-22)=31

and you could just barely run a short, if you never ever cross chain ever, and do not have much/any chain stay growth. but it would be super tight.

any bigger of a range (ie. 22/36 and 11-34) would absolutely require a mid-cage

 

[slyfink]

That's an odd setup...why the 32T - 28T front?

I've just been playing with various size rings in the past few years. I find a 28t granny gets me up everything I need here, with a 11-34 cassette. I was running 36t-28t last year, but found I was spending too much time in the 38f-34r combo and wearing out just one cog. So this year I dropped down to a 32t "big" ring, and feel that I'm using far more of my cassette now. I've lost a tiny bit of DH speed, but I only notice it on the road, where it doesn't count! The 28t granny gets used in a few rare circumstances. I've been trying to get a feel to see if I can go 1x10 with a 32 t front and an 11x36 rear. I think I could do it, but in certain circumstances it would be painful, and I'm not sure it's worth the cash outlay. I guess it depends on how seksy the new Shimano Zee is, and how convincing it's siren song is...

any bigger of a range (ie. 22/36 and 11-34) would absolutely require a mid-cage

I ran an 36t-28t front and 11x34 cassette for two years with my short cage derailleur, no problems. Like I said previously, you would have to be careful when cross chained in the small-small combo, but it's really not that hard to avoid. It hasn't happened to me yet.

 

[marshalolson]

I ran an 36t-28t front and 11x34 cassette for two years

that is a 31t capacity, exactly my example

28/34 = .823
32/36 = .889

so, 32/36 is about 8% taller of a gear. equiv to a 28/31 gearing.

 

[Pslide]

if you never ever cross chain ever...

But nobody cross chains, right? I mean, apart from my wife on her commuter, we all know better right? So does that mean you can alter your equation to only include gear combinations we actually use?

 

[dropmachine]

You also have to take into account the design of the bike, particularly the suspension used. If its a design with a lot of chain growth, you can tear your deraileur in half if you compress things when your chain is tight. Happened to me on a Krap pile ARmaggedon.

If you're on a bike that actually has working suspension though, you should be all good.

 

[marshalolson]

But nobody cross chains, right? I mean, apart from my wife on her commuter, we all know better right? So does that mean you can alter your equation to only include gear combinations we actually use?

you can manipulate the capacity formula to just the gears you would actually use, no problem. big big is the limiting factor of chain-length of course. if you only use the 3 easiest cogs religiously, with the small front ring, like you *should*, you can run a short cage with a dual ring, but will for sure have a ton of slack in the line if you shift to to a taller gear in the granny ring.

but i personally have managed to get into some funky gears when my brain is zapped and i am in full lactic-pain, while racing some times, and i am sure others have too...

 

[dbozman]

My experience is short cage with anything other than a single front ring is a bad idea, assuming a "normal" range cassette. I'm sure others can offer experience to the contrary. Mine is that accidentally cross-chaining when tired, suspension compresses and "pow."

 

[Jm_]

You also have to take into account the design of the bike, particularly the suspension used. If its a design with a lot of chain growth, you can tear your deraileur in half if you compress things when your chain is tight. Happened to me on a Krap pile ARmaggedon.

If you're on a bike that actually has working suspension though, you should be all good.

This.

Can't believe the number of posters above saying it depends on "gear spread" or "single vs double" and "nothing else". Yes, there is something else, something pretty darn important. On many bikes and applications it won't be a big issue, but it can be.