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  1. #1
    We're going down WHAT??
    Reputation: jonsocal's Avatar
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    Sram cassette 32tooth - What size "cage" derailer?

    I am refreshing my drivetrain on my Giant VT-1 and wanted to know what you all think is the best derailer for this set up? I have the new Sram PG-990 (the one with the red lockring and spine) 11-32 and a PC99 chain. Do I use the XT long cage or short cage rear derailer and why? (by the way, I am picking up all new chainrings for my Raceface Turbine crankset too.)

    Thanks,

    JK
    "Political correctness is tyranny with manners."
    - Charlton Heston

  2. #2
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    long (SGS)

    Unless you use less than 3 chain rings. The "short" mountain derailer is acturaly a medium cage (GS), Double chainring road bikes with tiny cassettes use SS cage (short).

    (# of teeth of largest cog - # of teeth of smallest cog) + (# teeth of big ring - # teeth of granny) = chain capacity.

    Don't buy into all the crap about the medium cage derailleur shifting better and "you shouldn't cross chain anyway". That is all B$. You will be in situations where you use the granny and the smallest cog. It happens. Your bike needs to be prepared.

    Just get a nice Deore derailleur, remove the cage (before you install it) and set the chain tension spring to the firm setting as you re-assemble it.
    Bankrupt the terrorists: commute by bike.

  3. #3
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    New question here. Deore??

    Quote Originally Posted by long_strange_ride
    Unless you use less than 3 chain rings. The "short" mountain derailer is acturaly a medium cage (GS), Double chainring road bikes with tiny cassettes use SS cage (short).

    (# of teeth of largest cog - # of teeth of smallest cog) + (# teeth of big ring - # teeth of granny) = chain capacity.

    Don't buy into all the crap about the medium cage derailleur shifting better and "you shouldn't cross chain anyway". That is all B$. You will be in situations where you use the granny and the smallest cog. It happens. Your bike needs to be prepared.

    Just get a nice Deore derailleur, remove the cage (before you install it) and set the chain tension spring to the firm setting as you re-assemble it.
    No kidding? Deore derailer? I am very fond of the deore disc brakes, but rear derailer? That is interesting. Does the XT have the same spring tension setting? I am probably going to go with the medium cage derailer. How do I know when my chain is tensioned correctly? That is the only thing keeping me from completing the bike refresh myself. "correct chain tension". What points of reference do I use?
    "Political correctness is tyranny with manners."
    - Charlton Heston

  4. #4
    1x9'er
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    Quote Originally Posted by jonsocal
    No kidding? Deore derailer? I am very fond of the deore disc brakes, but rear derailer? That is interesting. Does the XT have the same spring tension setting? I am probably going to go with the medium cage derailer. How do I know when my chain is tensioned correctly? That is the only thing keeping me from completing the bike refresh myself. "correct chain tension". What points of reference do I use?
    I think you're referring to chain length?

    I shorten the chain down to where there is enough chain to use the big front ring with the smallest 3 rear cogs and the small front ring the biggest 3 rear cogs and the middle ring with all the rear cogs. There is no need or reason to have the chain long enough to use the big ring and big cog together, that just contributes to extra chain slapping around and jumping off the front ring.

    The gear ratios start overlapping at about the 2nd to 3rd from smallest cog with the big ring, and 3rd to 4th from biggest cog and small ring, so there is no benefit to using big/big or small/small gear combos.

    Gearing example using typical 22-32-44 compact front rings and 11-13-15-17-20-23-26-30-34 9-speed rear cogs:

    Front:Rear = GearRatio (divide # of rear teeth by # of front teeth).

    22:34 = 1.55
    22:30 = 1.36
    22:26 = 1.18
    22:23 = 1.05

    32:34 = 1.06
    32:11 = 0.34

    44:11 = 0.25
    44:13 = 0.30
    44:15 = 0.34

    The gear ratio overlaps for cogs used with the big or small rings versus with the middle ring in this example start at the 7th cog/big ring and 4th cog/small ring (assuming cog # 1 is the biggest cog ). A typical 3x9, 27-speed bike really only has 14 different usable gear ratios. The other 13 gear combinations are just overlapping ratios that are not needed.

  5. #5
    Weird huh?
    Reputation: cmdrpiffle's Avatar
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    What Long Strange Ride said...

    Really sound advice!

    Don't buy into all the crap about the medium cage derailleur shifting better and "you shouldn't cross chain anyway". That is all B$. You will be in situations where you use the granny and the smallest cog. It happens. Your bike needs to be prepared.

    Just get a nice Deore derailleur, remove the cage (before you install it) and set the chain tension spring to the firm setting as you re-assemble it.

  6. #6
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    Quote Originally Posted by jonsocal
    ...Does the XT have the same spring tension setting? I am probably going to go with the medium cage derailer. How do I know when my chain is tensioned correctly? That is the only thing keeping me from completing the bike refresh myself. "correct chain tension". What points of reference do I use?
    Look at the exploded view diagram where it says 9. The right side of the line points to a theaded pin which holds the cage on. This pin is removed with a 1.5 mm hex. There are 2 holes in the cage plate which don't really show up. The unit comes with the spring set in the soft position hole.

    XT is the same as Deore. XTR cages are held on differently.

    Short-chaining your bike is risky business. I try to carry a few spare links on the trail so I don't have to run short chain even in emergencies.

    To combat chain slap, I shift ino large-large combos. I haven't had much trouble throwing or dropping the chain using my new XT top swing front D.
    Bankrupt the terrorists: commute by bike.

  7. #7
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    I'll give it a shot tonight!!

    Once I have handed out of my 10 bags of candy, I will get to this on my new derailer. Thanks fo rthe input. I like the idea of changing the tension instead of the short chain idea. I have broken a couple of chains in my day and don't want to end up having to puch my bike back to the trailhead anytime soon!

    John K
    "Political correctness is tyranny with manners."
    - Charlton Heston

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