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  1. #1
    Senior Member mparker326's Avatar
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    So why does the chain keep skipping on my Motobecane Grand Record?

    I asked for help in the mechanics section a few days ago and didn't really get anywhere. I am hoping you folks over here know more about the idiosyncrasies of a vintage bike.

    I bought a '74 Motobecane Grand Record a few weeks ago. Beautiful bike (pictures forthcoming) It has a Campy NR triple with a Campy Rally derailer. The freewheel was a '72 Suntour 14 to 34 5 speed. Suntour barcon shifters.

    I took apart everything and cleaned & greased.

    I took it out for its maiden voyage and the chain skipped. It was the original chain. I measured and it was stretched, so I replaced with a KMC Z 5 to 7 speed chain and made it the same length as the original. I made sure there were no stiff links. I saw no noticeable wear on the freewheel or chain rings so I left those alone. It rode better but the chain skipped under load in 4th & 5th gear in all 3 rings. I had the freewheel replaced with a 14 to 28 Shimano cheapo. I rode it for a few days and didn't notice any skips (maybe it was still in process of tightening up?). Now the skips under load are back in 4th & 5th.

    When I had the freewheel replaced at the LBS, I asked about the chain length because I was going from a 34 down to a 28. He checked the combinations and said that it was a little long, but it was in the low/low combos that I shouldn't be riding in anyway. I removed a couple links after it started skipping again and it hasn't helped.

    My chain rings don't look worn and since they are 74 NR, I'd rather not replace. Also, if they were worn, I'd expect it to skip more in the middle ring vs. big ring, but I can make it skip in all 3 rings. Could there be issues with my Rally derailer (which is beautiful btw. and I'd really like to keep)? Could low chain tension be causing this?

    Any pointers from ya'll who have been there done that?

    Here is a pic of my front chainrings and the original Suntour freewheel.




  2. #2
    www.theheadbadge.com cudak888's Avatar
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    Try another rear freewheel - was the cheapo Shimano FW, without a doubt, new and un-used? Same for the KMC chain?

    -Kurt

  3. #3
    Senior Member mparker326's Avatar
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    Yes, the freewheel was unused and the chain was unused. I did ride the new chain for a couple small commutes on the old freewheel. Could this have damaged my chain?

    Should I just start over with a new freewheel and a new chain?

  4. #4
    Senior Member due ruote's Avatar
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    Quote Originally Posted by mparker326 View Post
    Yes, the freewheel was unused and the chain was unused. I did ride the new chain for a couple small commutes on the old freewheel. Could this have damaged my chain?

    Should I just start over with a new freewheel and a new chain?
    I can't imagine that the new chain would be worn from that much riding. Try a different fw like Kurt said. Also check the rear derailleur; make sure the pivots aren't sloppy and the pulleys are vertically aligned.

    I'd also re-check the chain length per Sheldon Brown's advice: The best technique for setting chain length is to thread the chain onto the large/large combination, without running it through the rear derailer. Mesh the two ends on to the large chainwheel so that they could be connected (outer link meets inner link), then make the chain one complete link (one inch) longer than that. In almost all cases, this will give the optimum length.

    Like you said, I'd leave the rings out of it. You'd be lucky to find vintage rings as good as what you have on there.

    Look forward to seeing the full-bike pics.

  5. #5
    Senior Member mparker326's Avatar
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    Quote Originally Posted by jbonamici View Post
    Also check the rear derailleur; make sure the pivots aren't sloppy and the pulleys are vertically aligned.
    I thought about that but this quote from Sheldon in his derailer adjustment article threw me off:
    Note, wide-range Campagnolo derailers have cages that are not intended to be vertical; the lower pulley is farther outboard than the jockey pulley.
    If this statement is true then how could I tell if it was aligned correctly?

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    Personally, I would be looking for a bent frame or dérailleur dropout. Right now, I've got a slightly bent rear triangle (chain stays) and I get the exact same problem in those two gears. Years ago, I had a bent dropout on a bike that did the same thing. But that's just my personal experience speaking....

    -Jon

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    Quote Originally Posted by joninkrakow View Post
    Personally, I would be looking for a bent frame or dérailleur dropout. Right now, I've got a slightly bent rear triangle (chain stays) and I get the exact same problem in those two gears. Years ago, I had a bent dropout on a bike that did the same thing. But that's just my personal experience speaking....

    -Jon

    Good points...

  8. #8
    Senior Member mparker326's Avatar
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    Quote Originally Posted by joninkrakow View Post
    Personally, I would be looking for a bent frame or dérailleur dropout. Right now, I've got a slightly bent rear triangle (chain stays) and I get the exact same problem in those two gears. Years ago, I had a bent dropout on a bike that did the same thing. But that's just my personal experience speaking....

    -Jon

    Thanks, I'll check that. Hopefully, that isn't the case.

    Rear dropout:


  9. #9
    Old Skeptic stronglight's Avatar
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    I would guess a bent dropout hanger... or a bad derailleur. Either would be an easy fix.

    I see you have a Campy dropout, so that should work easily with a bike shop's dropout alignment tool which just screws into the hanger in place of a derailleur, and with the wheel still on... so that should cost very little for a shop to check and to set if necessary - in around 1 minute.

    A new rear derailleur is always nice too. The early Campy Rally was a decently functioning piece and really pretty, but (sorry) simply no contest against even a cheap modern Shimano Deore.

    With luck it will not be the entire rear triangle, but still something which can be fixed.

    Good Luck and keep us posted.

  10. #10
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    Quote Originally Posted by mparker326 View Post
    Thanks, I'll check that. Hopefully, that isn't the case.

    Rear dropout:

    You know, looking at the dropout, I wonder if maybe it's gotten mucked up. I can't tell from the photo, but I remember reading somewhere (mabye these forums) of a dropout that was so worn and eaten up that it caused other problems. Yours doesn't look anywhere near as bad as the picture i saw then, but it's also worth considering. I think the problem was made obvious by the fact that the wheel could move even when tightly clamped down (qr). Again, I'm just shooting in the dark, this time from something read. ;-)

    -Jon

  11. #11
    SNARKY MEMBER CardiacKid's Avatar
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    It could be caused by worn out cables or cable housing. I would replace those if they look like they have any wear. You should probably also make sure the place where the RD cable goes around the bb is smoooth and clean. If the cable is hanging up anywhere, it could cause the chain to skip when it becomes unhung or when the frame flexes under load.

  12. #12
    Senior Member due ruote's Avatar
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    I'm intrigued by the bent hanger theory but can't quite get my brain around the mechanics of it - anyone care to explain?

    If you have another RD, you could try swapping it and see if the problem persists.

  13. #13
    Senior Member fender1's Avatar
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    Is the rear deraileur a Campy Gran Turismo? If so, I had one on my 1972 P-15 Paramount (with a Campy NR triple) and it shifted terribly! I would second trying a different deraileur and replacing the cables and housing if they are worn or if they are original to the bike. FWIW I am running a Shimano Crane (rebranded Letour) long cage on my Paramount and using a friction, bar-end shifter, the deraileurs have no trouble shifting through a modern 9 speed SRAM 11-32 cassette. I am using a nine speed chain as well.

    EDIT: I re-read and saw it was a Rally rd. I have not used one of those but pastorbob had one on a recent build and disliked it so much ne switched it out for a Huret(?) Duopar. He was also running a Campy NR Triple.
    Last edited by fender1; 10-08-08 at 07:40 PM.

  14. #14
    Too many bikes bikemore's Avatar
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    I am interested in this thread because I have a chain skipping problem also. Problem occurs on multiple rear
    cogs (where I keep this bike I typically only use the smallest three cogs). Will only happen for a short time on
    my hour long ride - again it can happen on any cog. Freewheel is Shimano 600 six speed.
    Chain has less then 150 miles on
    it. Freewheel looks fairly new, plus it occurred with two different freewheels. I don't believe the rear hanger
    is bent, but I will look into replacing the cables. Old and not serviced recently.
    Trek 560.

    Good to know others have seen sort of a mystery problem.

  15. #15
    Señor Member USAZorro's Avatar
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    Quote Originally Posted by bikemore View Post
    I am interested in this thread because I have a chain skipping problem also. Problem occurs on multiple rear
    cogs (where I keep this bike I typically only use the smallest three cogs). Will only happen for a short time on
    my hour long ride - again it can happen on any cog. Freewheel is Shimano 600 six speed.
    Chain has less then 150 miles on
    it. Freewheel looks fairly new, plus it occurred with two different freewheels. I don't believe the rear hanger
    is bent, but I will look into replacing the cables. Old and not serviced recently.
    Trek 560.

    Good to know others have seen sort of a mystery problem.
    How far back in the dropout is your axle? One reason for chain skipping is insufficient chain wrap.
    The search for inner peace continues...

  16. #16
    Old Skeptic stronglight's Avatar
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    Quote Originally Posted by bikemore View Post
    "I am interested in this thread because I have a chain skipping problem also.... I don't believe the rear hanger is bent..."
    "Bent" is a relative term, and it is not always obvious to the eye. A hanger can be bent just slightly down (inward) or twisted slightly fore or aft. One way to make sure the derailleur is aligned parallel (to at least the wheel - and on all axis) is to use the hanger alignment tool which follows around the circle of the rim to guarantee that it's guide pin is touching the rim at same distance on all points around the wheel. You can check out this procedure here on the Park Tool website: http://www.parktool.com/repair/readhowto.asp?id=39

    It's done wonders on a few badly shifting bikes I've encountered... but maybe this is just being overly optimistic.

    If you have a spare derailleur to borrow onto the bike temporarily, this would perhaps be a good starting point which you could use for making a direct comparison yourself, and without using any fancy shop tools at all.

    The Rally, although not my favorite in terms of flawless operation (nor is any 70s Campy derailleur for that matter) seems to work pretty decently on my Paramount with a Campy NR Triple and a 14-31 Regina freewheel (definitely not my favorite freewheel either). To my eye it looks a lot like a Shimano long cage Titlist derailleur of the mid 70s, and it was dramatically different in design than any other 70s Campy derailleurs (a Good difference).

    Good luck to all. And remember: "once you eliminate the impossible, what remains, however improbable, must be the truth" - Sherlock Holmes

  17. #17
    Randomhead
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    Quote Originally Posted by jbonamici View Post
    I'm intrigued by the bent hanger theory but can't quite get my brain around the mechanics of it - anyone care to explain?
    Because of the closeness of the dérailleur to the rear cogs, a bent hanger would induce a sharp angle in the chain. Thus the chain wouldn't want to ride on the cog. To counteract that bend, you would have to shift the derailleur such that it was not really where it would normally be to happily ride on the cog. So it would be very touchy.

  18. #18
    Too many bikes bikemore's Avatar
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    The chain wrap looks good, the wheel is more or less in the center of the
    drop out (Trek drop outs are pretty short).

    It will be a week or two or more before I have a chance to get the bike
    to a shop to check the alignment. Just looking at it the alignment looks
    fine, but I know enough to use a tool to works much better then just looking.

  19. #19
    Senior Member
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    Quote Originally Posted by stronglight View Post
    ...is to use the hanger alignment tool which follows around the circle of the rim to guarantee that ...
    Yes, a simple check to insure the derailler jockey wheels are running in the same line as the wheel, and the freewheel. Quite easy if you have the tool.

  20. #20
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    Quote Originally Posted by USAZorro View Post
    How far back in the dropout is your axle? One reason for chain skipping is insufficient chain wrap.
    I've never found position in the dropout to be an issue, given everything else correct. They're made to be used the entire length, depending on your tastes.

  21. #21
    Senior Member due ruote's Avatar
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    Quote Originally Posted by unterhausen View Post
    Because of the closeness of the dérailleur to the rear cogs, a bent hanger would induce a sharp angle in the chain. Thus the chain wouldn't want to ride on the cog. To counteract that bend, you would have to shift the derailleur such that it was not really where it would normally be to happily ride on the cog. So it would be very touchy.
    How far back in the dropout is your axle? One reason for chain skipping is insufficient chain wrap.
    One thing the OP didn't make clear is whether it's skipping between gears, or whether the chain is just riding up on the small cogs. If the hanger were bent, wouldn't you expect to have some trouble in all the gears? The fact that it's limited to the small cogs makes it seem to me like an insufficient chain wrap issue, as USAZorro points out.

  22. #22
    Senior Member
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    Quote Originally Posted by jbonamici View Post
    makes it seem to me like an insufficient chain wrap issue, as USAZorro points out.

    Could be: hard to diagnose without the bike in front of us. If so, I'd make the chain just long enough to handle the big/big combo, though of course you'd never ride there...

    Also, with a misaligned dropout hanger I'd suspect the problem would be magnified on the smaller cogs.

  23. #23
    Senior Member mparker326's Avatar
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    And the verdict is . . .

    I stopped by the LBS at lunch.

    He checked the derailer hanger with the tool & said that it was near perfect and far better than most he sees.

    He suspected the Rally. He felt of the spring tension and said it was very weak. He didn't know enough about the old stuff to see if he could adjust the tension. He gave me a loaner derailer to try out. I swapped it out at lunch and bingo no skips.

    So can I save my Rally? Is there a way to adjust the spring tension? Attached is the '74 Campy catalog description. Looks like it is part 813A.
    Attached Images Attached Images

  24. #24
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    Quote Originally Posted by mparker326 View Post
    So can I save my Rally? Is there a way to adjust the spring tension?
    If you remove the lower pivot bolt to release the cage there are 3 holes which hold the spring. Move to another hole to add tension.

    Might try pulling the spring and winding it up too, or replacing if you can find one...

  25. #25
    www.theheadbadge.com cudak888's Avatar
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    Is the cage pivot spring the same between the NR and the Rally? If so, even a Nuovo Gran Sport spring would work.

    -Kurt

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