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rear derailleur

Discussion in 'Chit-Chat' started by cruiserman, Jul 19, 2005.

  1. cruiserman

    cruiserman

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    I've adjusted the rear derailleur on my bike as best I can, but it rides on the frame when the chain is on the small cog. I've gone to the limit of the b-screw adjustment, and I've checked the chain length several times. I'm thinking the derailleur spring is worn. Any way to verify it without plunking down the $100 for a new one?

    Part is XTR M952.

    thx, eric
     
  2. wesintl

    wesintl

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    Turn clockwise the lower ot right limiting screw. A worn spring should not affect the limiting screws. I would suspect worn bushings at the hanger screw. If you hold the deraileur cage from the rear do you have alot of slop side to side? You really shouldn't have any and it does affect shifting since there is side play. How many miles or how old?
     
  3. Owyhee Jackass

    Owyhee Jackass

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    Don't put the chain in the small cog ;)


    I suck at bike maintenance and adjustments. Right now I can't ride in my middle chain ring and it takes a minute and a half to shift to the lower ring.
     
  4. Cruiserdrew

    Cruiserdrew On the way there SILVER Star

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    XTR stuff is so excellent, that I doubt the spring is bad. It sounds like your chain may be too long. Was it replaced previously? If you have the tools to cut the chain, try taking out 2 links and see where you are. Any chance you could post a picture? Do you have the indexing set right so that it shifts exactly at the "click". You shouldn't be using the small chainring small cog, but then I assume you know that.
     
  5. Cube Dweller

    Cube Dweller Moderator

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    Check the alignment of the derailler hanger. If the chain hits the frame on the small cog, something else is going on if you can't adjust it out.
     
  6. MJM

    MJM SILVER Star

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    Limit is it

    The limit is the issue put chain in center front cog, while turning crank adjust the scew in your derailure will go into place. FYI a trick that I have done in the past for worn out springs is to Zip tie the middle of it it works great for grip shifts.
    MJM
     
  7. roscoFJ73

    roscoFJ73

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    Maybe a good clean would help,anyway derailleurs arent expensive.
     
  8. cruiserman

    cruiserman

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    I'll post a pic tonight after I get home.

    The bike is used and I suspect abused. I broke the chain and replaced it with a whipperman. At the same time I replaced the cogs (XT). I matched the length of the old chain, and it was wrong. I used the big cog, big chainring method to determine length, and I've gone 1 link more and less. I just read on a site about seeing if the derailleur is straight up and down with cog in 5th and on 2nd chainring. Will also verify alignment. It looked good last night.

    Limit screws seem fine. It shifts great down to 2nd smallest cog, then the derailleur hits the frame as it tries to move to the small cog.

    I haven't taken a derailleur apart before, and I'm not inclined to do so, since I'd be time ahead just replacing the thing. Cheapest one I've found is $80 + shipping on closeout. I was going to stick with same part rather than go to 960 rapid rise variety ($135).

    I'll check side to side play.

    thanks for the help.
    eric
     
  9. cruiserman

    cruiserman

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    Not sure what you mean. Can you elaborate? by front cog do you mean chainring? Which adjustment screw? Where do you put the zip tie?
    eric
     
  10. DenverCruiser

    DenverCruiser

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  11. Hakkalugi

    Hakkalugi

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    Sell that heap off and buy a singlespeed! :D
     
  12. cruiserman

    cruiserman

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    OK. Vertical alignment from the rear looks good. With chain on 2nd chainring and 5th cog, the cage is nearly vertical viewed from the side.

    Here is a picture of the derailleur in 2nd chainring and small cog. Notice how the cage around the upper pulley contacts the frame? That's keeping it from properly shifting to the lower cog.
     
  13. Mr. Toad

    Mr. Toad

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    Solution is here!

    Your chain's too long.

    Re-size the chain by placing it on the big front chainring and the smallest rear cog. The length is correct when the pulleys are vertical in this configuration.

    Trust me, I'm a roadie. ;)
     
  14. wesintl

    wesintl

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    First off you can't work on a bike upside down. :rolleyes: :D

    and take the pic of the gears vertically from rear to front. :grinpimp:
     
  15. miked

    miked

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  16. cruiserman

    cruiserman

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    Roadies don't have suspension movement ;). Cage is vertical with chain on big ring and little cog.

    I played with it a bit, and it will shift to low cog now. Vertical alignment looks good. I'm not happy with it close to the frame, but it works. LBS said they have a b spring in stock, and I will probably replace it.

    However, I neglected to mention another very disconcerting problem: the chain will skip under load while on the 2nd chainring. Not on 1rst or 3rd chainring, just 2nd. I imagine the chainring is worn, but it's hard to tell. It doesn't skip up or down the cog.

    All part of the fun of buying a used mountain bike. I should have kept my old one.
     
  17. Cube Dweller

    Cube Dweller Moderator

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    Skipping under load on the middle chainring after replacing a chain typically means the chainring has stretched along with the old chain. Toss it.

    To ballpark chain length put the chain on the largest chainring and smallest cog. The derailler cage should be perpendicular to level ground. This will get you close, assuming you run a std cluster, like 13-30. You may need to add or subtract a couple links.

    Make sure the derailler hanger is perpendicular to the axis of the rear wheel. Make sure your wheel is centered in the dropouts and the wheel is dished. Make sure the axle spacing is accurate.

    Enjoy.
     
  18. wesintl

    wesintl

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    Yep. replace middle chain ring. FWIW I stick with matching mfg on the chain and cog. Over the years i've come to find a shimano chain works best on a shimano cog. JMHO.
     
  19. T Y L E R

    T Y L E R

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    Just cram a washer on the 13 side .. move the frame out a little. :D



    TY
     
  20. cruiserman

    cruiserman

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    Got any chainring recommendations? I'm not inclined to go XT again, and they are hard to find anyway. XTR is too expensive, and I suspect won't mount to my XT cranks.

    Blackspire and Syncros get good reviews, but not easy to find online.

    My current set is 4 bolt, 22/32/44.