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Thread: Help with XT rear derailleur please

  1. #1
    Senior Member axertes's Avatar
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    Default Help with XT rear derailleur please

    Edit: Problem Solvered

    but there's pretty pictures to look at still


    So I'm a noob at maintenance. I have a XT shadow long-cage.

    I slipped off a 6" high rock and landed straight on my rear derailleur. Now it skips regularly, about 4 times per chain revolution. It was working perfectly before it argued with the rock.

    I adjusted the H and L screws, because I initially thought that'd be out of whack, but it SHIFTS fine, but still skips. The skipping is equally bad in any gear.

    It skips on the pulley wheel indicated in this pic, but not the other. It consequently skips on the sprocket. Yes I know it needs a clean.



    The B-tension screw is not touching the mech no matter what sprocket I'm on. When I spin the pedals and 'adjust' the b-tension with my hand it doesn't get any better.

    What concerns me is that the cage itself doesn't seem to be straight compared to the angle of the chain on the sprocket. In this pic you'll see it's not 100% straight. Actually, the pic doesn't do it justice. It's 'un-straighter' than it shows.



    Should it be absolutely, 100% straight? If it should, I fear I bent the derailleur hanger, which I don't have the tool to fix (unless I do the ghetto shifter jobbie on it).

    Those sexy plastic things with reflectors are due to me being 'between pedals' (i.e. I was really clever and sold my old ones before I got new ones. Why? I have no idea). Shut up :p

    Help anyone?

    Thanks in advance,

    Geoff
    Last edited by axertes; 11-02-2008 at 03:08 AM.

  2. #2
    ex offender S.'s Avatar
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    The H and L screws are limit screws - they simply set the upper and lower limits that the derailleur can shift to. If the gears are skipping, they're NOT the cause - once they're set they should never need to be touched again.

    What's happened is that either your derailleur or your hanger (or both) is bent, or that somehow bashing your derailleur has managed to pull hard on your cable and either stretch the cable or compress the housing slightly. If the derailleur and hanger are both not visibly bent (there is a certain amount of tolerance for bending, ie a bent derailleur/hanger isn't necessarily inoperable) then you need to try adjusting the barrel adjuster for the cable. Shadows don't have barrel adjusters on the derailleurs (like SRAM stuff but unlike other Shimano stuff) so you have to use the one on the shifter (it makes no difference which you use, the shifter and derailleur barrel adjusters both do exactly the same thing). Check either the Shimano or Park Tools website for how to adjust this properly cos I cbf explaining right now.

    And yes if you're wondering, your derailleur cage should be straight up/down (looks like it's slightly twisted to me though?). Like I said, you can tolerate a certain amount of bending but once it gets beyond a certain point it'll never work no matter how you adjust it. The fact that you say it skips in all gears points to it being misaligned equally in all gears which makes me think it's probably just your cable needing adjustment. If the derailleur isn't sitting in line with the cogs on your cassette, the chain will be pulled slightly off the top pulley, so don't stress too much about that.
    Try adjusting the cable properly, if that doesn't fix it then something is bent - hopefully the $30 hanger not the $150 derailleur.

  3. #3
    Senior Member AngoXC's Avatar
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    Good point S
    From the pictures, the mech looks slightly twisted...although it could just be the angle of the picture. You could say heat the mech up (soften the metal...just like my glasses) and attempt to reallign it but it will never be perfect as such again.

    You might also want to check the links in your chain (any bent ones) as well as the teeth on the cassette...all are possibilities...that said, you have gone to a pretty big effort to decribe the said problem so one would think something would have been spotted then...couldnt hurt anyways.

    Other points to keep an eye on are your hanger. I twisted a Deore mech once while the Deore was fine, the hanger was twisted enough to raise alarm.

    Other then that, Im sorry I cant be a better help!

    (I lol at your pedals...)

    Good luck with it all mate.
    Last edited by AngoXC; 10-02-2008 at 10:57 PM. Reason: ...names

  4. #4
    Senior Member axertes's Avatar
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    Quote Originally Posted by S. View Post
    The H and L screws are limit screws - they simply set the upper and lower limits that the derailleur can shift to. If the gears are skipping, they're NOT the cause - once they're set they should never need to be touched again.
    Yeah, I thought if it only needed a slight adjustment I could adjust both limits slightly, but in hindsight I see how that is completely and utterly stupid. Now I have the chore of readjusting those too :(

    AND I SAID SHUT UP ABOUT MY PEDALS!

    Thank you both. I'll research how to adjust Mr. Barrel Adjuster. And report back with any results.

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    Check that you don't have a sticky link. Make sure when you take your chain through the rollers on your derailer the chain can bend enough to go around them smoothly.

    If not find the one that skips add lots of lube and bend sideways back and forth untill it moves smoothly.

    This used to happen to me all the time on my xc bike and I used to freak out that it was my derailer.

  6. #6
    Senior Member axertes's Avatar
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    Unfortunately it's not that, I already checked by putting a little mark on the links that skipped with a paint pen, and they were different each time.

    Still haven't learnt about barrel adjusters. Meesa lazy.

    Edit: regarding barrel adjustment.

    Park Tools webbie says this:

    Changes to inner wire tension are made at the adjusting barrel. Adjusting barrels may be located either at the rear derailleur or at the shift lever. The goal of adjusting the indexing is to find the tightest inner wire tension setting that will allow good shifting to the gears normally used. This will allow the longest lasting indexing adjustment as the system wears and the cable system stretches with use. To find the tightest inner wire setting, you will purposely make the setting too tight then relax tension slightly. There are two basic symptoms for a "too tight" inner wire. These are a rattling noise from the chain rubbing against the next cog inward, and a slow or hesitant outward shift. These are symptoms for rear derailleurs that sit outward when inner wire tension is released.

    1. Set limit screws (if not already done).
    2. Shift chain to outermost rear sprocket (smallest). Shift chain to outermost (largest) chainring in front.
    3. Test initial inner wire tension. Pedal a normal cadence and shift rear derailleur with one click on lever. Use care to only move lever one position. If derailleur moves one sprocket, tension is adequate.
    4. If derailleur fails to shift one sprocket, inner wire may be too slack. Turn barrel adjuster fully into derailleur body (or shift lever) then turn counter clockwise two turns to allow for index adjustments. Loosen inner wire pinch bolt and gently pull on inner wire with fourth hand tool or pliers to remove slack. Tighten inner wire pinch bolt.
    5. If derailleur will not shift one sprocket after removing slack in "d", return lever back to outermost sprocket position and increase inner wire tension by turning barrel adjuster counter-clockwise 1/4 turn and attempt shift again.
    6. Shift to second sprocket in rear. Pedal and increase inner wire tension by continuing to turn adjusting barrel counter-clockwise until a definite rattling is heard. Rattle is from chain scrapping against next sprocket.
    7. Once a too-tight rattle is achieved, turn barrel adjuster 1/4 turn clockwise, to release inner wire tension, and pedal again. Listen and look for signs of scraping or rattling. Continue turning barrel adjuster 1/4 turn clockwise at a time until rattle disappears.
    8. Shift derailleur one sprocket inward at a time, listening for signs of rattle, indicating a too tight inner wire. Turn adjusting barrel 1/4 turn clockwise to eliminate rattle. Note: Do not attempt shift to largest rear sprocket while in largest front sprocket. This gear is normally not used and adjusting tension to this shift may compromise other commonly used gears.
    9. Shift to innermost (smallest) chainring and check gears again. If no rattling is present, index adjustment is done.
    That doesn't seem to mention anything that pertains to my predicament.

    BUT when it's in the highest gear (smallest sprocket), there's lots of slack in the cable. Like, enough that I can put my hand between it and the top tube without stretching the cable. It still changes fine though. Is that normal? I've never noticed that slack before, but I've never really adjusted this derailleur before either.
    Last edited by axertes; 11-02-2008 at 01:38 AM.

  7. #7
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    Quote Originally Posted by S.
    The H and L screws are limit screws - they simply set the upper and lower limits that the derailleur can shift to. If the gears are skipping, they're NOT the cause - once they're set they should never need to be touched again.

    What's happened is that either your derailleur or your hanger (or both) is bent, or that somehow bashing your derailleur has managed to pull hard on your cable and either stretch the cable or compress the housing slightly. If the derailleur and hanger are both not visibly bent (there is a certain amount of tolerance for bending, ie a bent derailleur/hanger isn't necessarily inoperable) then you need to try adjusting the barrel adjuster for the cable. Shadows don't have barrel adjusters on the derailleurs (like SRAM stuff but unlike other Shimano stuff) so you have to use the one on the shifter (it makes no difference which you use, the shifter and derailleur barrel adjusters both do exactly the same thing). Check either the Shimano or Park Tools website for how to adjust this properly cos I cbf explaining right now.

    And yes if you're wondering, your derailleur cage should be straight up/down (looks like it's slightly twisted to me though?). Like I said, you can tolerate a certain amount of bending but once it gets beyond a certain point it'll never work no matter how you adjust it. The fact that you say it skips in all gears points to it being misaligned equally in all gears which makes me think it's probably just your cable needing adjustment. If the derailleur isn't sitting in line with the cogs on your cassette, the chain will be pulled slightly off the top pulley, so don't stress too much about that.
    Try adjusting the cable properly, if that doesn't fix it then something is bent - hopefully the $30 hanger not the $150 deraileur
    Another great response by the infamous S.

    Something else to consider and inho most likely is that you have bent your hanger (as mentioned) and/or your frame (hopefully not and very unlikely the latter).

    Your LBS will have a tool to determine if this is the case. Get it looked at as it was something I physically couldn't see but was enough for my shifting to be very ordinary.
    Last edited by Emmett; 11-02-2008 at 01:38 AM.

  8. #8
    Senior Member axertes's Avatar
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    Quote Originally Posted by Emmett View Post
    Something else to consider and inho most likely is that you have bent your hanger (as mentioned) and/or your frame (hopefully not and very unlikely the latter).
    A bent frame would be extremely unlikely. It was a low velocity slip-off-a-rock-and-land-on-my-derailleur incident.

    It was such a minor impact that I'm surprised it would be able to bend the derailleur hanger, actually, even though so far that is the most likely scenario.

    I looked down and just saw the derailleur bent up as far as it would go, with my 80kg of manliness baring down upon it.

  9. #9
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    Quote Originally Posted by axertes View Post
    A bent frame would be extremely unlikely. It was a low velocity slip-off-a-rock-and-land-on-my-derailleur incident.

    It was such a minor impact that I'm surprised it would be able to bend the derailleur hanger, actually, even though so far that is the most likely scenario.

    I looked down and just saw the derailleur bent up as far as it would go, with my 80kg of manliness baring down upon it.
    I have bent a hanger before and had absolutely no idea how it happened. All i knew was that my shifting was non-existant. As said previously, get it checked out at your LBS and measured as I personally wasn't able to see it when it happened to me.

    I have also bent an XC 6061 frame (without bending the hanger) and didn't feel it.

  10. #10
    Senior Member axertes's Avatar
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    Problem Located!





    How much is a new pulley wheel and/or LBS labour likely to set me back?

    If I remove the little 3mm allen bolt that holds the pulley wheel in am I going to send loaded springs flying all over my workshop*?

    Edit: upon further examination I realised that no, I won't. So THAT'S what hat little Phillips-head-screw-pin-thingy is. So can you replace the wheel bit and keep the little ceramic bush and stuff?



    I might have to further embarrass myself with plastic reflecty pedals.




    *kitchen. I also have a great maintenance stand* in it

    *door frame to hang bike from by saddle
    Last edited by axertes; 11-02-2008 at 02:31 AM.

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