I set the S.I.R. 9 up as a 2-speed today- Mtbr.com
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  1. #1
    Nat
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    I set the S.I.R. 9 up as a 2-speed today

    In honor of both President Washington and President Lincoln, I set the Niner up as a 2-speed. I have a 32/22 off-road gear plus 36/18 commuting-slash-downhill gear. The cogs are Surly (22T) and King (18T) placed side-by-side without any intermediate spacer. The asymmetry of the Surly cog works in my favor here since it makes a little more room for the chain. The rings are both Salsa, with the outside (36T) turned inwards so that the chainring bolts set within the recessions and stabilize the ring nicely. The 1/8" chain even fits the setup as long as I turn the master link around to face inwards. There's barely any change in chain tension when I change gearing.

    Yes, I had the day off.
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    Last edited by Nat; 02-21-2006 at 08:56 AM.

  2. #2
    giddy up!
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    Cool setup...something like that would be nice for days when you feel like riding an hour or soo to the trailhead, riding in the dirt, and then riding home.

    B
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  3. #3
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    Very cool. Food for thought...
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  4. #4
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    Could I do that with a 32/18 and a 36/14 set up?
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  5. #5
    Nat
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    Quote Originally Posted by Enoch
    Could I do that with a 32/18 and a 36/14 set up?
    Probably. The necessary chain length might change a hair and you'd have to take up tension, but you might get lucky like me and not have to.

  6. #6
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    Add the teeth up...

    Quote Originally Posted by Enoch
    Could I do that with a 32/18 and a 36/14 set up?
    The idea behind the multi-gear, no chain tension adjustment necessary multi-gear setup is to have the number of teeth for each combination add up to the same number: So 32/18 and 36/14 should work since they both add up to 50 teeth. I've got my SIR9 set up with 32/20 and 34/18 and it works nicely. Just be sure to measure the chainline out for both combinations. One can usually just put two cogs side by side (if they're thick ~1/4"), but Endless recommends a 1mm spacer between their cogs, which is what I did. That lines up the cogs well with the chainrings.

    Go for it! It's awesome to not have to spin your a$$ off to get to the trail (and to have an easier or harder gear if you need it).

    Do note that there will likely be a slight chain tension variance between the two combinations, but it shouldn't be enough to worry about.

    Jeremy

  7. #7
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    very cool. I may need to try that with my commuter/cross rig which I take on occasional single track but would do so more often if it had more trail friendly gearing.
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  8. #8
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    Would it work on a single speed hub?

    I have a Paul Word hub, could it work on that if I swapped out the free hub for the gears? Or are cassette hubs the only way to do it? Great idea, I want !

  9. #9
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    Dos Eno Freewheel...

    Quote Originally Posted by moondoggy
    I have a Paul Word hub, could it work on that if I swapped out the free hub for the gears? Or are cassette hubs the only way to do it? Great idea, I want !
    Is the only way to run 2 gears on a threaded SS hub AFAIK.

  10. #10
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    Flip Flop

    It's the same idea oas a filp flop hub. Phil and WI both make a flip flop with threads for a freewhhel on both sides, I believe. Flip the hub and move the chain over to shift. I use an ENO flip flop on my Bontrager and I like a higher gear on the Fixed side. The chain still works out just fine, but the rear brake barely hits the machined surface, so I usually just ride with the cable open and use the front brake only. I don't go that fast on the fixie anyway....
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  11. #11
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    Quote Originally Posted by Enoch
    Could I do that with a 32/18 and a 36/14 set up?
    If you can tolerate some chain slack, around 7/8". The perfect chainstay size for 32x18 is 17.214", for 36x14 its 17.16".

    To keep an exact chain fit you must add the same number of teeth to the chainring and the cog. for instance 32x18, 34x20, and 36x22 all a need 17.214" chainstay.

  12. #12
    Nat
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    Quote Originally Posted by pacman
    If you can tolerate some chain slack, around 7/8". The perfect chainstay size for 32x18 is 17.214", for 36x14 its 17.16".

    To keep an exact chain fit you must add the same number of teeth to the chainring and the cog. for instance 32x18, 34x20, and 36x22 all a need 17.214" chainstay.
    If he has an EBB, sliding dropouts, or some other tensioning device, then the chainstay length isn't critical.

    Even though you keep the same sum of teeth, there's still some length difference due to the fact that necessary chain length is a function more of the chainring and cog radius (or perhaps better yet, radians -- y'all remember radians?) rather than quantity of teeth. On my bike, the high gear needs a slightly longer chain (a couple of mm. maybe) even though the number of teeth totals the same as the low gear, but the difference is small enough that I don't think I'll need to adjust the EBB.

  13. #13
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    Having the chain a little slack on the faster gear would be just fine, The mountain/off road tension needs to be on the money. It's still obtainable either way since I have sliders on my bike. Thanks for the answers.
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    Quote Originally Posted by Nat
    If he has an EBB, sliding dropouts, or some other tensioning device, then the chainstay length isn't critical.

    Even though you keep the same sum of teeth, there's still some length difference due to the fact that necessary chain length is a function more of the chainring and cog radius (or perhaps better yet, radians -- y'all remember radians?) rather than quantity of teeth. On my bike, the high gear needs a slightly longer chain (a couple of mm. maybe) even though the number of teeth totals the same as the low gear, but the difference is small enough that I don't think I'll need to adjust the EBB.

    With horizontal drops do you think I'd need a chain tensioner device ?

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    Doesn't quite work like that see this recent thread on the SS forum.

    Doesn't take much adjustment though - I've been running this setup for quite a while on my bike.
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  16. #16
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    Quote Originally Posted by Nat
    If he has an EBB, sliding dropouts, or some other tensioning device, then the chainstay length isn't critical.

    Even though you keep the same sum of teeth, there's still some length difference due to the fact that necessary chain length is a function more of the chainring and cog radius (or perhaps better yet, radians -- y'all remember radians?) rather than quantity of teeth. On my bike, the high gear needs a slightly longer chain (a couple of mm. maybe) even though the number of teeth totals the same as the low gear, but the difference is small enough that I don't think I'll need to adjust the EBB.
    That's why adding the same number to chainring and cog works (perfectly). The radian effects cancel. But you do need to take/add chain links.

    On Nat's bike that small difference means ~3/4" of chain sag, but some misalignment of the chain line can compensate for that - make the chain tighter.

  17. #17
    Nat
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    Quote Originally Posted by moondoggy
    With horizontal drops do you think I'd need a chain tensioner device ?
    Horizontal drops count as your chain tensioning device, so you're good to go. I've never owned a bike with horizontal dropouts, but it seems as if it'd be a major pain to remove the wheel. Would you have to break the chain? You'd at least need tools, right? With a QR setup it takes me maybe 30 seconds (if even that) to switch gears. Do you have a freewheel or cassette type rear? I'm not sure why people prefer the freewheel style. The cassette seems to have more advantages.

  18. #18
    Nat
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    Quote Originally Posted by pacman
    That's why adding the same number to chainring and cog works (perfectly). The radian effects cancel. But you do need to take/add chain links.

    On Nat's bike that small difference means ~3/4" of chain sag, but some misalignment of the chain line can compensate for that - make the chain tighter.
    Hmmmm...I'm not sure I follow. 4 teeth on the ring takes up less distance around the circle (smaller percentage of the circumference) than 4 teeth on the cog (unless they're the same size), right?

    My chain sag is way less than 3/4". It's maybe 2mm. I don't need to remove or add any links. Are you using someone's calculator? Maybe there's a glitch in their programming?

  19. #19
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    Quote Originally Posted by Nat
    Hmmmm...I'm not sure I follow. 4 teeth on the ring takes up less distance around the circle (smaller percentage of the circumference) than 4 teeth on the cog (unless they're the same size), right?

    My chain sag is way less than 3/4". It's maybe 2mm. I don't need to remove or add any links. Are you using someone's calculator? Maybe there's a glitch in their programming?
    Enter your data here http://www.peak.org/~fixin/personal/fmu/php/javafmu.php
    When you click on the individual gearing the "perfect" chainstay will be displayed. And voila, the rule holds. As for the sag, the figure is for cog and chainring aligned, a small error in aligment can pull the chain tighter. One hopes the BB and axle are parallel. Your case is one or the other.

  20. #20

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    I can see how that works if the cogs are the same size, but if you did that you would need a longer chain anyhow.

    What we're trying to do here is get a different ratio with the same chain length and chainstay length. This is not possible precisely, the best you can do is the add two/four, take two/four and you get pretty close. But because you're dealing with different size circles and the same change to their circumference this change is going to effect the chainstay length (i.e. tension).

  21. #21
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    My LBS here in MN is now stocking Niners. Saw a freaky sexy "Kermit" green SIR yesterday. Wow. Very light relative to my KM. Light as in I would likely snap it light. I love 853 but fear I would terminate the frame on the first grunt inducing climb.
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