Chain jumping on cassette gears

Discussion in 'Cycling Equipment' started by Pingouin, Jun 27, 2007.

  1. Pingouin

    Pingouin New Member

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    Hello! I'm new here. It's not like I never had any problems, but I always managed to solved them somehow... up to now.

    I've got a racing bike, a Campag Athena 2 chainring set, and a 8 speed cassette. My front gear shifter is Shimano 105, the rear one Shimano 600. The brake/gears levers are shimano 600.

    This week, I changed the following:
    * worn out SRAM PC-51 chain to SRAM PC-58, compatible 8 gears. The original chain was 133cm, so I removed 4 links on the new one to get the same length. I use a power link.
    * worn out Shimano 52/44 chainrings with AT 52 and Stronglight 42 chainrings, compatible Campag. The 52T has the arrow away from the crank as I was told to do.

    Now, whenever I put a minimum of torque in my cranks, the chain jumps on the rear cassette from one gear to one of its neighbour, and back, and over and over again. That is no matter how finely I try to shift. The cassette does not seem to be worn out, and I didn't touch the gear shifters at all. I also decided to change the jockey/tension pulleys since those were a bit worn out as well, but it didn't help.

    It was fine before I changed the chain. Anyone has any idea what is going on and how I can fix it please?

    Thanks in advance!
     
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  2. sideshow_bob

    sideshow_bob New Member

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    Rear cassette needs to be changed. Might not look worn, but symptoms suggest it is. I'll bet the second you change it, it'll be fixed.

    --brett
     
  3. Pingouin

    Pingouin New Member

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    Augh, my budget is already gone, and I don't even have the tools to change the cassette myself. The missus is gonna kill me, check the obituary section in tomorrow's paper :eek:
    By the way, just to make sure: the chain jumps from gear to gear, it doesn't jump ABOVE the gear, if you see what I mean.
     
  4. jhuskey

    jhuskey Moderator

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    Have you tried adjusting the cable housing tension? Mis-adjustment can cause the chain to jump around.
     
  5. Pingouin

    Pingouin New Member

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    Thanks to both of you! My bike is my little sweetie (it probably costs more than my car!), and I'm desperate to get it back properly on the road.

    jhuskey: yes, actually, when I arrived at uni, I realised my cable housing was routed below the skewers instead of above it. I put it back above, but didn't think much of it. I'll see tonight if it helps!

    I'm also looking into cassettes prices. If it keeps on skipping tonight, I'll probably go for one.
    The cassette I have now is a SACH LY 97, 12/19T. I'm thinking about getting this Shimano HG50 (if needed):
    http://www.cyclebasket.com/products.php?show=416

    Do you people have any idea if it will fit? I also need to get a chain whip, and a lock-ring. Will the same lock-ring work on both the old SACH and the potentially future Shimano? I'm keen on investing on the tools if it's an investment which can save me money later, and I'm keen on learning how to do the stuff myself (my car rarely ever see a mechanic!).

    I'm sorry, I'm a total newbie. I never changed cassette before, and yesterday was the first time I ever changed chainrings!
     
  6. p38lightning

    p38lightning New Member

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    He's probably right, but let me suggest a troubleshooting techneque to maybe prove this. Take the cassette sprockets off and turn them around, that is put the side facing in to the spokes out. When you do this the lead edge of the sprocket notch which the chain bears on becomes the trailing edge and you now have a less worn "new" lead edge .If this doesn't fix your problem it may not be the cassette. If it does it's the cassette all right. Since the shifting ramps and timing are changed the shifting will degrade. THIS IS NOT A FIX ONLY A TROUBLESHOOTING TECHNEQUE.
     
  7. Pingouin

    Pingouin New Member

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    Loosening the cable housing didn't help, and it seems on closer inspection that the chain is indeed jumping OVER the gear, not from gear to gear! The person I bought the bike from told me to change the cassette as well.
    So I'll be ordering a Shimano HG50 today seeing that there's no way but to go over the budget, and hopefully, sort it out in the next few days.

    Thanks again everyone! Hopefully, I'll be back on a proper bike soon, the £30 mountain bike I'm using these days is really rubbish in comparison.
     
  8. meehs

    meehs New Member

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    It's almost without question a worn cassette. You replaced the other drive components without replacing it. If your chain was significantly worn (which it most likely was since you were running it on worn chainrings) and you ran it that way for any length of time, the cassette almost certainly wore to match the chain. So when you put a new chain on, the chain pitch doesn't match the tooth profile of the cassette and it therefore skips. I've seen this a lot. If you run your new chain on the worn cassette it'll wear that new chain out really fast.

    Get yourself the $10 Park chain-wear indicator tool and check your chain often. As soon as it's worn .75%-1%, put a new chain on. This will prevent a worn chain from destroying your other drivetrain components. Chains aren't cheap these days but it's a lot more expensive when you need to replace cassettes and chainrings too!

    Even though I'm supposed to know better, I ignorantly ran a worn chain on my single-speed last summer until the teeth on the freewheel and chainring were literally hooked! Luckily on a SS it's just one cog and one chainring that need to be repalced.
     
  9. Pingouin

    Pingouin New Member

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    Thanks!
    I contacted the shop in Wales from which I buy my parts, and he said that since my SACH cassette is so old (and since I can't recall what my hubs are off hand), he cannot guarantee that a Shimano cassette will actually fit (although he said that since my levers and rear gear is Shimano 600, the cassette is probably compatible Shimano as well).
    So now I've found a colleague with a HG40 cassette on his rear wheel. I'll try to mount my cassette on his wheel next week, and if it fits, I'll be buying a HG50 cassette the same day.
    My mountain bike is so crappy that the gears are not even low grade Shimano, so I can't use this cassette. The rear gears looks like raw bits punched out of a metal sheet... and I'll have to keep using it for another week probably.
    Cheers all!
     
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