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Thread: 12-26 to 11-28

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    CAT5 joe_5700's Avatar
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    12-26 to 11-28

    I switched my cassette on my Jamis from a 12-26 to a 11-28. My Jamis has 2200 8 speed shifters, 2200 FD and 5600 105 RD. When I changed the cassette I knew I would need to add a few links. I tried the 12-26 chain just to see what would happen and it was a mess. I had a new chain, so I cut it like the 12-26 but with 2 more links. The shifting is fine on the 28 side of the cassette, but once you get to the middle the RD skips gears like crazy and it seems like I am always in between gears in the middle of the cassette on to the 11. Do I need to add more links, or does the RD simply need adjustment for the 11-28? Yes, the 11-28 casssette is an 8 speed like the 12-26.

    thanks,
    Joe

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    Did you need the extra links ( you probably did, but shouldn't be guessing? you need to get the chain length, right, how to guides can be found on the Park tools website. For the chain skipping, this is more likly an adjustment issue, rather than a chain length issue, again, check the Park site for RD setup details.

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    Ride, Wrench, Swap, Race dddd's Avatar
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    Very likely the derailer cable (and limit screws) would need some fine-tuning, but probably not much at all unless the cassette were a different brand.

    The derailer should also have it's B-tension screw adjusted so the pully doesn't quite touch the tips of the largest sprocket's teeth.
    The head of this screw faces the rear of the bike, but it's not screwed into the derailer knuckle like the other two screws. Check this clearance while in both chainrings, but check the small ring first.

    Could the new cassette not be stacked perfectly with the spacers? Does the space between cogs seem to vary as the cassette turns?

    Looking at the chain (from BEHIND the bike) can you see even gaps between the chain and the next-larger sprocket (and between that same bit of chain and the thicker of the two derailer cage plates?
    Those are good visual checks for the cable adjustment! Check this with the chain on one of the larger sprockets, but not the largest.
    <<Very dirty sprockets would need to be scraped clean first>>.

    Tug on the exposed cable wire along the chainstay, and observe smooth sliding of the cable through the cable housing loop going to the derailer. The cable should not have much friction. Smooth take-up, and smooth return. Also do the same check along the downtube, checking now for friction in the cable guide below the bottom bracket. These often get gunked up with drink residue.

    A new chain on well-used sprockets would tend to skip under load, worse when you pedaled hard, and worse in the smaller chainring where max chain tension is greater.

    If you have removed the cable from the pinch bolt on the derailer, note the cable must be positioned accurately in the groove (or between guide pins) where the cable pinch bolt/washer secures the cable. This affects the leverage (travel ratio) of the shifter/derailer and assures accurate and consistent indexing.

    I'm also tending to think the cable housing perhaps got pulled out of one of the ferrule caps and is now not seating in fully.

    Also, were any spacer rings present with either cassette that fit on the inner end? Are the cogs all secured tight?
    Are the chains both of similar outside width?

    Note that a 2-tooth change in cassette sprocket size only changes the chain length requirement by 1 single link, but you can't adjust 1 link only pairs.
    Last edited by dddd; 10-19-11 at 04:39 PM.

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    Cable adjustment or a worn chain.

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    joe: Is the 11-28 cassette new or used? Your new chain on a worn cassette could be trouble. Is the cassette assembled correctly, that is, are any needed spacers present and in the correct positions? If everything is assembled correctly, including the cable attachment and all ferrules present and correctly seated, and there is free movement of the cable (especially check the last loop going into the derailleur) you should be able to get it right by adjusting the system. Follow these instructions from start to finish without skipping any steps: http://www.parktool.com/blog/repair-...nts-derailleur

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    CAT5 joe_5700's Avatar
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    I should have mentioned that I am using a brand new chain and cassette (Forte brand). The extra links were needed because when I used the chain that was being used on the 12-26 the shifting was a complete mess. The shifting is good with the new chain and cassette only on the upper part of the cassette in both cogs.

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    I find the "Largest Cog and Largest Chainwheel Method" to work well for chain length
    http://www.parktool.com/blog/repair-...-length-sizing
    scroll down a bit

    after that, go through the derailleur adjustment process dsbrantjr posted above
    http://www.parktool.com/blog/repair-...nts-derailleur
    Last edited by imi; 10-20-11 at 07:57 AM.

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    Senior Member oldbobcat's Avatar
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    Quote Originally Posted by joe_5700 View Post
    I should have mentioned that I am using a brand new chain and cassette (Forte brand). The extra links were needed because when I used the chain that was being used on the 12-26 the shifting was a complete mess. The shifting is good with the new chain and cassette only on the upper part of the cassette in both cogs.
    Inconsistent shifting on opposite sides of the cassette usually indicates a bent derailleur or derailleur hanger. The reason you're only seeing this after swapping the chain and cassette is probably because of the changed angles of the derailleur pulley arm.

    Rear derailleurs are not rocket science if you have the right tool. Have your local shop check your alignment.

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    CAT5 joe_5700's Avatar
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    Quote Originally Posted by oldbobcat View Post
    Inconsistent shifting on opposite sides of the cassette usually indicates a bent derailleur or derailleur hanger. The reason you're only seeing this after swapping the chain and cassette is probably because of the changed angles of the derailleur pulley arm.

    Rear derailleurs are not rocket science if you have the right tool. Have your local shop check your alignment.
    No, the RD is not bent at all. My shifting was perfect with my 12-26 setup.

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    Senior Member mikeybikes's Avatar
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    If your chain was too short, you would have only noticed problems in the big chain ring and the largest cog on the cassette.

    Sounds like your derailleur is poorly adjusted.
    My Bikes: 2009 Breezer Uptown EX | 1980 Miyata Six Ten | 1970 Hercules Three-Two-Speed
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    Ride, Wrench, Swap, Race dddd's Avatar
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    Typically, derailers which appear to be straight, i.e. the pullies (as a pair) are in-line with the engaged sprocket, will work as good as they look. A clean cassette makes this easier to see, especially over the larger cogs.
    I have yet to encounter a shifting problem that was caused by a bent derailer or hanger which wasn't apparent to the naked eye.
    One does have to look from the top down, with the pullies arranged vertically, AND from the rear of the bike with the pullies arranged horizontally, so some shifting to different sprocket sizes makes this inspection possible.

    It is also possible that the derailer and hanger could be bent in opposite directions, but this doesn't seem to happen and in this case the alignment would be seen to go out of whack when the pulley cage rotated to different positions.
    I will say again, one needs to look from behind, observing the clearance gaps to each side of the chain on the short span from the top pulley to the cassette. Clearance there should allow the chain to engage fully and quietly.

    Do also check that the pulleys both turn freely, as any friction will rob tension from the chain precisely where it needs to be tensioned as it engages the cassette!

  12. #12
    Senior Member oldbobcat's Avatar
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    Quote Originally Posted by joe_5700 View Post
    No, the RD is not bent at all. My shifting was perfect with my 12-26 setup.
    Duh. That's what I'm trying to tell you. Just because the derailleur shifted OK with the 12-26 doesn't mean that the alignment is perfect. Changing the chain length often exaggerates misalignments that were previously too insignificant to notice.

    Aside from incorrect cog spacing or the wrong size chain, the only reasons for a derailleur to index perfectly on one end of the cassette and not on the other end are: a worn out derailleur with loose knuckles, loose jockey wheel, or worn out jockey wheel; a bent derailleur; or a bent derailleur hanger. Well, I've also seen problems where the chain was too short, pulling everything so tight that it behaved like a worn out derailleur, but from your description this doesn't seem to apply.

    I'm also assuming that your shifter works and your cable is clean and without kinks--it worked well with the old cassette and chain.

    With 9- and 10-speed drivetrains and short road chainstays derailleur alignment is crucial and often can't be evaluated by just looking at it.

    Oh, hell, fiddle with the b-screw long enough and I'm sure that'll do it.

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