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Re: [rootsradicals] Chain Length Question

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  • Rick Pickett
    Links, Your chain will have some slack to it due to the unsupported span from chainring to cogset, and depending on the strength of your derailleur spring. For
    Message 1 of 7 , Mar 1, 2009
      Links,

      Your chain will have some slack to it due to the unsupported span from chainring to cogset, and depending on the strength of your derailleur spring.

      For proper length, shift the chain to the granny chainring up front and the smallest cog in the rear.  On the bottom section of chain, pull the chain forward until the chain is pulling the rear derailleur cage enough to not have contact btw your cage and chain.  Remove the links needed to achieve this tension.  If a small amount of rubbing is occurring, that's fine since you should never be in small/small.

      The reason you tension in this gear setup is because this is the most compressed your rear derailleur will ever get.  As you shift up in gears, both front and rear, more chain will wrap around the greater circumference of gears pulling more tension on your rear derailleur, bringing the cage forward.

      Just be sure that you can get into the largest cog in front and rear (although you should never ride in this setup for the same reasons as small/small (too much strain on the chain)).  If your derailleur is being overstretched due to too few links, you could destroy your derailleur, break a chain, etc.

      Hope this helps.  Anyone else toss in your 2¢ if I'm missing anything.

      Rick

      On Mar 1, 2009, at 9:04 PM, Beau wrote:

      I just got back my 700c model Xtra from the bike shop and the chain 
      has a lot of slack. I was wondering how long the chain should be? I 
      have a feeling too many links were added. Thanks.

      -Links


    • Bruno
      Hi! I was thinking about how your derailer cage length could be involved in this to see if there would be anything to add to what Rick already said (everything
      Message 2 of 7 , Mar 2, 2009
        Hi!

        I was thinking about how your derailer cage length could be involved in this to see if there would be anything to add to what Rick already said (everything needed to know) and found this post about cage length and chain lenght on http://forums.mtbr.com/showthread.php?t=284688 that can be an interesting read too.

        Cheers,
        Bruno
      • davidmoskovitz
        I saw a nice mod in the xtracycle forum to increase chain tension, and I tried it myself with excellent results. A picture is really the easiest way to
        Message 3 of 7 , Mar 12, 2009
          I saw a nice mod in the xtracycle forum to increase chain tension, and I tried it myself with excellent results. A picture is really the easiest way to describe it:

          http://tinyurl.com/baxjmk

          http://www.flickr.com/photos/davidmoskovitz/2375136151/

          Run a longish spring from the lower rear deraileur pulley to the rear bridge of the Free Rad, or BD. I did this by drilling a small hole in the derailleur cage behind the pulley, in an area that doesn't interfere with the chain. I used an M2 or M3 bolt to attach a Sturmey/Archer hub-gear barrel adjuster and chain, becuase it was handy, and becasue it provides an easy way to adjust the length of the spring or to detatch it altogether. Then I used a p-clamp or old tail-light bracket to attach the spring near the rear bridge. I ended up buying a handful of springs, but in the end I used a fairly stout spring.

          It works very well. There seems to be enough distance between the derailleur cage and the rear bridge so that the lateral motion of the derailleur cage is not significantly impeaded by the spring.

          I was almost embarrassed to post the picture, since it prominently displays a Tourney derailleur. For what its worth, it was free. It also works fine, and seems to soak up more chain than some higher-end rear gorillas I've used. There's an XT getting dusty on the mantle now.

          I'll try to put the photo in the Rootsrad-group-space, too.
        • John W
          Hi, One thing to keep in mind when reading the advice for shifting and chain length is that gears that are made unusable on short-tail bikes because of chain
          Message 4 of 7 , Mar 15, 2009
            Hi,

            One thing to keep in mind when reading the advice for shifting and chain length is that gears that are made "unusable" on short-tail bikes because of chain line issues may work perfectly well on long-tail bicycles because of the longer chain. For example, it is generally advised to avoid the large cog/large chainring combination because the chain has so far to go in a lateral direction it creates more friction, noise and stress on the entire drive train. But with a longer chain the angle of deviation from a perfect chain line is less so this is not as big an issue. You still have the chain tension issues but as mentioned in other posts this can be solved by a longer cage or other more clever means. So another advantage of a long-tail bike is you get more usable gears and consequently don't have to shift between chainrings as often, which is a nuisance in general but even more so under load.

            Aloha, - John

            --- In rootsradicals@yahoogroups.com, Bruno <bsantos@...> wrote:
            >
            > Hi!
            >
            > I was thinking about how your derailer cage length could be involved in this
            > to see if there would be anything to add to what Rick already said
            > (everything needed to know) and found this post about cage length and chain
            > lenght on http://forums.mtbr.com/showthread.php?t=284688 that can be an
            > interesting read too.
            >
            > Cheers,
            > Bruno
            >
          • Mark Garvey
            I rode recumbents for quite some time, and still have one in my garage awaiting some repair work to be functional. As a side note...The REASON it has been
            Message 5 of 7 , Mar 15, 2009
              I rode recumbents for quite some time, and still have one in my garage awaiting some repair work to be functional.

              As a side note...The REASON it has been sitting for over 2 years is because the Xtracycle and the E-assist are both on my upright (Wedgie, Ass hatchet) bike, and the X gets RIDDEN and the recumbent has been sitting!

              ANYWAY, on the extremely long chain lines on Trikes and recumbents, you nearly HAVE to have some sort of idler wheel.  They are easy enough to set up,   Make a plate with a bolt welded to it that fits a skate board wheel.  Clamp said plate to a convienent spot on the bike frame and run the chain over this wheel.  It helps if you make a groove in the wheel that will keep the chain tracking and an L bracket to keep it from bouncing off. If you make a double wheel you can have the chain run across it in BOTH directions.  My Terra Trike had TWO of these and it did not seem to detract from performance enough to feel.

              It worked great and was a fun bike!

              MArk

              On Sun, Mar 15, 2009 at 3:03 PM, John W <john.p.wendell@...> wrote:
              Hi,

              One thing to keep in mind when reading the advice for shifting and chain length is that gears that are made "unusable" on short-tail bikes because of chain line issues may work perfectly well on long-tail bicycles because of the longer chain. For example, it is generally advised to avoid the large cog/large chainring combination because the chain has so far to go in a lateral direction it creates more friction, noise and stress on the entire drive train.  But with a longer chain the angle of deviation from a perfect chain line is less so this is not as big an issue.  You still have the chain tension issues but as mentioned in other posts this can be solved by a longer cage or other more clever means.  So another advantage of a long-tail bike is you get more usable gears and consequently don't have to shift between chainrings as often, which is a nuisance in general but even more so under load.

              Aloha, - John

              --- In rootsradicals@yahoogroups.com, Bruno <bsantos@...> wrote:
              >
              > Hi!
              >
              > I was thinking about how your derailer cage length could be involved in this
              > to see if there would be anything to add to what Rick already said
              > (everything needed to know) and found this post about cage length and chain
              > lenght on http://forums.mtbr.com/showthread.php?t=284688 that can be an
              > interesting read too.
              >
              > Cheers,
              > Bruno
              >




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