1. The most important thing about buying a new bike is to make sure it fits. The only way you'll know if the bike is right for you is to size up the bike and make sure that the bike's geometry matches your body's geometry. Ask questions and do some research.
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  1. #1
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    WTF am I doing? Rear Derailleur HELP!

    Okay, so I'm still in the learning phases - I've watched the video's on youtube and I've read the forums, why is this still so confusing to me?

    I am understanding how to fine tune your derailleur's, thanks to the wealth of adjustment videos on youtube and the knowledge here. However I'm having a problem with my LX rear derailleur.

    When I'm in the smallest/lowest sprocket in the front, and the smallest/highest sprocket in the back the rear derailleur has the chain touching itself. (should you even be in this gear config when riding? is that crossing the chain? if so what exactly does that mean?) Getting back to what I mean about touching - the two small cogs on the rear derailleur are almost on the same horizontal level, the bottom small cog being in the rear. This causes the chain on the way to the small lower cog to touch the chain that just left the lower cog thats on its way to the front of the drivetrain to touch. This is confusing I know, maybe I'll try to get a picture up or something. How do you adjust the derailleur angle to fix this problem?

    Any help is appreciated.

  2. #2
    g3h6o3
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    Quote Originally Posted by silkworm13
    Okay, so I'm still in the learning phases - I've watched the video's on youtube and I've read the forums, why is this still so confusing to me?

    I am understanding how to fine tune your derailleur's, thanks to the wealth of adjustment videos on youtube and the knowledge here. However I'm having a problem with my LX rear derailleur.

    When I'm in the smallest/lowest sprocket in the front, and the smallest/highest sprocket in the back the rear derailleur has the chain touching itself. (should you even be in this gear config when riding? is that crossing the chain? if so what exactly does that mean?) Getting back to what I mean about touching - the two small cogs on the rear derailleur are almost on the same horizontal level, the bottom small cog being in the rear. This causes the chain on the way to the small lower cog to touch the chain that just left the lower cog thats on its way to the front of the drivetrain to touch. This is confusing I know, maybe I'll try to get a picture up or something. How do you adjust the derailleur angle to fix this problem?

    Any help is appreciated.
    This happens when you're not using the right length of derailleur cage or if your chain is too long. What are your cassette and chainring sizes? What length cage RD are you running?
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  3. #3
    FasCat Coaching
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    First, that's major cross gearing and you shouldn't be riding in those gears. Secondly, you should adjust your chain length so that there is tension on the derailleur. Sounds like your chain is a bit to long
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  4. #4
    tlg
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    Quote Originally Posted by silkworm13
    When I'm in the smallest/lowest sprocket in the front, and the smallest/highest sprocket in the back the rear derailleur has the chain touching itself. (should you even be in this gear config when riding? is that crossing the chain?
    Yes this is crossing. Don't do it. Stay away from small/small and big/big.

    if so what exactly does that mean?
    This is your situation.

    Chains are meant to carry their loads in a straight line. The more side load you create (as above) the weaker the chain is. You'll cause more chain wear, ring/sprocket wear, and possibly pop a chain link.

    Getting back to what I mean about touching - the two small cogs on the rear derailleur are almost on the same horizontal level, the bottom small cog being in the rear. This causes the chain on the way to the small lower cog to touch the chain that just left the lower cog thats on its way to the front of the drivetrain to touch. This is confusing I know, maybe I'll try to get a picture up or something. How do you adjust the derailleur angle to fix this problem?
    Very confusing but think I get what you're saying.

    Are you sure you have the chain routed properly through the derailleur?

    Does your derailleur look something like this?

    It shouldn't if you're in small/small.

  5. #5
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    Quote Originally Posted by tlg
    Yes this is crossing. Don't do it. Stay away from small/small and big/big.

    This is your situation.

    Chains are meant to carry their loads in a straight line. The more side load you create (as above) the weaker the chain is. You'll cause more chain wear, ring/sprocket wear, and possibly pop a chain link.

    Very confusing but think I get what you're saying.

    Are you sure you have the chain routed properly through the derailleur?

    Does your derailleur look something like this?

    It shouldn't if you're in small/small.
    It actually looks like the opposite of that. When I'm on the small sprocket in the front and the small sprocket in the back (which i now know to stay away from).

  6. #6
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    Quote Originally Posted by silkworm13
    It actually looks like the opposite of that. When I'm on the small sprocket in the front and the small sprocket in the back (which i now know to stay away from).
    so it looks like the diagram and not the photo? your 2 jockey wheels are touching? You need a chain breaker. Do you have shimano or SRAM chain? you most likely need to remove a few links until there is tension on the derailleur pulling it away
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  7. #7
    Dirt Deviant
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    Did you recently replace your chain? Or derailuer?
    Did you do it yourself? Or did a shop do it?
    Sounds like your chain is a few links too long. Chains come longer than they normally need to be, and you must remove a few links to get proper tension.

    The way I determine how many links need to be removed is to put the front in the small chainring, and the rear in the smallest cog, then take up a little slack by hand in the chain until the chain is not touching itself, and the jockey pulleys are not horizontal.
    This usually equates to removing 3 links.
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  8. #8
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    the gear setup is like the first diagram, and the derailleur is too loose - not pulled tight towards the bottom bracket like the second picture, but all the way back with the "bottom" wheel back behind the "top" wheel.

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