Advertise on Bikeforums.net



User Tag List

Results 1 to 8 of 8

Thread: Chain jam

  1. #1
    Senior Member
    Join Date
    Apr 2006
    Posts
    171
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Chain jam

    My cannondale caad 9 with ultegra components just started to develope a problem. I know that you should not cross chain but when you do and pedal backwords the chain drops down the rear cassette and jams. I know the standard answer is dont cross chain the bike but it never did this before so I was wondering what to look for. One other detail is that I just switched to a new chain. It didnt make any diffrence.

  2. #2
    Junior Member
    Join Date
    Sep 2011
    Location
    KSEA
    Posts
    9
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Probably you just need to adjust low limit screw on the rear derailleur?

  3. #3
    Senior Member
    Join Date
    Apr 2006
    Posts
    171
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    No, that didnt work. The rear derauler shifts up through the gears just fine and sits directly under the big sproket on the rear cassette. This only jams pedaling backwards which from what I understand the rear derauler doesnt act as a guide

  4. #4
    Senior Member
    Join Date
    Sep 2010
    Posts
    2,832
    Mentioned
    4 Post(s)
    Tagged
    0 Thread(s)
    Drtumolo: It is possible that as your cogs have worn in it shifts easier when you back pedal. Running cross-chained will exacerbate this tendency as well as causing excessive noise and wear on your chain and gearing. There are comparable gear ratios available without cross-chaining; why persist in doing it? No good reason to back pedal, either, except to position your pedals for mounting the bike and moving off.

  5. #5
    slow as I ever was Ex Pres's Avatar
    Join Date
    Dec 2007
    Location
    an imposter living in the 35223
    Posts
    5,743
    Mentioned
    5 Post(s)
    Tagged
    0 Thread(s)
    Backpedaling is a good way to check for tight links, but other than that - what's the point?
    72 special CNC ______ 72 Frejus (ala Legnano) _73 Holdsworth Record
    80 Ranson__________ 80 unknown French____ 83 Trek 600 (620 styled)
    85 Gianni Motta_____ 90 Miele Gara ________ 02 Casati Dardo #1
    02 Casati Dardo #2 __ 03 Casati Dardo ______ 08 BF IRO (fixed/SS)
    09 Dogma FPX magn_ 10 Vassago Fisticuff (IGH)

    For Sale: _________ 78 Raleigh Professional __ 82 Peugeot PXN10
    85 Trek 560_______ 88 Guerciotti GLX

  6. #6
    Senior Member
    Join Date
    Apr 2009
    Location
    New Rochelle, NY
    My Bikes
    too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
    Posts
    22,014
    Mentioned
    60 Post(s)
    Tagged
    1 Thread(s)
    derailleur systems are designed to tun in one direction only. For them to work the guide (ie derailleur) has to be before the sprocket, otherwise the sprocket is trying to shift it in the derailleur. If you can't visualize this imagine trying to deflect or block a pass while standing beyond the receiver.

    The reason your system auto shifts when backpedaling in crossed combinations or from the innermost cassette sprocket is that the unguided chain is trying to find a straight line path and so will try to change sprockets to one closer to the side it's coming from. Sometimes new systems are more forgiving, but with chain and sprocket wear they might get less so. OTOH, I've seen new drive trains that were extremely unforgiving of backpedaling while crossed mellow as the sprockets wore in.

    There is no adjustment or modification that can change this because the chain is running unguided in reverse, but if you get used to how it shifts, you can drop the RD one or two shifts so it matches the sprocket the chain has selected, thus avoiding the jam.
    FB
    Chain-L site

    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  7. #7
    Senior Member
    Join Date
    Apr 2006
    Posts
    171
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Thanks for all the info. I do know that it is not good to cross chain the bike and also know that backpedaling is not productive. I just noticed that it changed since it never did this before. I can live with it just wondering what changed.

  8. #8
    Senior Member
    Join Date
    Jun 2010
    Location
    Pearland, Texas
    My Bikes
    Cannondale, Trek, Raleigh, Santana
    Posts
    5,675
    Mentioned
    6 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Drtumolo View Post
    My cannondale caad 9 with ultegra components just started to develope a problem. I know that you should not cross chain but when you do and pedal backwords the chain drops down the rear cassette and jams. I know the standard answer is dont cross chain the bike but it never did this before so I was wondering what to look for. One other detail is that I just switched to a new chain. It didnt make any diffrence.
    Might simply be that the old chain was too dirty to be flexable and the new chain is too new to be flexable. In either case it's a moot point.

    Brad

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •