** Follow up to "F'ing chain keeps falling OFF!!!!"- Mtbr.com
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  1. #1
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    ** Follow up to "F'ing chain keeps falling OFF!!!!"

    OK.....
    here is my setup- 16t rear cassette cog from a shimano 8 speed cassette. Cog is in like new condition, not bent or worn. I'm using aluminum and steel cassette spacers from a few old cassettes and cut PVC pipe to space out the chainline. (which happens to be perfect. If its off, i dont know how the hell im gonna get the line any straighter!) I am using a brand new Deora 8/9 speed hub on a mavic 221 rim. Wheel is true, no proken spokes and spokes are properly tensioned. I have 2 tuggernuts, rear QR skewer, and RaceFace evolve DH cranks and BB. I dont have a singleator or anything like that. I noticed that the chainring was set oblong, so i loosened all the chainring bolts, spun the cranks a bunch, then slowly re-tightened them all.

    Before i went for a ride yesterday, i stopped into a shop that knows singlespeeds. He told me i needed a new chain, which i did because my 9speed compatible was a little twisted. I bought a Sram Single Speed chain. He told me "wider is better" I put it on w/ the same amount of links as before.

    I made sure that the chain had no slack. I tightened the tuggernuts to right before the point when you can't freely backspin the pedals because of resistance.

    OK, im all ready to go for a nice, slightly technical, slightly hilly 20 mile ride.

    First banked hill....

    Chain falls off the rear cog. F*&% POS!

    I tighten up the chain a little more.

    Same thing about 3 miles later. "F*&%!"

    I tighten it up a little more

    Repeat above for the rest of the ride...

    I didnt really tighten the chain to the point of where it doesnt backspin freely. I tightened it to where you could back spin the cranks about 1 rotation. But it seemed that it always fell off the rear, and tightening made it fall-off less often.

    In frustration, i devised a little concotion on the rear freewheel... Check it out. I havent ridden on it yet. Im hoping it will solve my problems.

    Here are some pictures.
    Attached Images Attached Images

  2. #2
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    I made that rear chain guide out of two 21 tooth 8 speed cassette cogs. I bench grinded them and knife-edged them. I knife edge them so it would a little smoother alignment (should it try to derail).

    Here's some more pics...
    Attached Images Attached Images

  3. #3
    One gear to rule them all
    Reputation: 32seventeen's Avatar
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    Is the chain falling off the front or the rear?
    First, I would repalce the rear cog with a BMX cog, like a nova tec or sh!tmano. Once replace the cog, those home made guards should not be nessesary.
    You did not mention what front chainring you are running, if it is a ramped ring, I would replace that with a SS non-ramped ring.
    Todd............. If you can't be kind, at least have the decency to be vague

  4. #4
    Probably drunk right now
    Reputation: Ken in KC's Avatar
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    Chainline....

    Based on your picture, it still looks like your chainline is off.

    Also, rather than using a gear from a cassette, buck up and spend the $10 for a Shimano BMX cog and be done with the shift ramps in back.

    As 32:17 mentioned, if your front ring is ramped, get rid of that as well.

    Ken

  5. #5
    self destructive
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    is the pvc pipe you are using cut perfectly stright?
    When it rains it pours.

  6. #6
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    I agree with the other post...

    I bet 99.9% that your chain dropping problem is comming from the rear cog you are using....RAMPED. Drop the rear cog and get something that is not ramped.....and same story for the front, if you are using a ramped ring, dump it for a SS ring.

    KMan

  7. #7
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    From the picture, it looks like your rear wheel might not be in the frame straight. if you look closely you can see that the chain looks like it bends a little bit right at the rear cog. So, check this stuff: is your hub in the dropouts straight? if your wheel isn't dished properly, the hub won't be straight when the rim is centered between the chainstays.
    --- FeelsGood

  8. #8
    Retro Grouch
    Reputation: aka brad's Avatar
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    You need to be more engaging...

    Quote Originally Posted by KMan
    I bet 99.9% that your chain dropping problem is comming from the rear cog you are using....RAMPED. Drop the rear cog and get something that is not ramped.....and same story for the front, if you are using a ramped ring, dump it for a SS ring.

    KMan
    ..your chain that is. Here is the photo of your setup with the ramped cog, next a comparison of cogs and finally a photo of my bike with a BMX cog. You can see that the BMX cog has twice the engament of your HG cog. Remember all non-BMX cogs are designed to derail. The only reason they don't is there is a jockey pulley on a derailleur standing several mm away holding the chain on the cog.

    BTW, I like the cog guide; it's not a new idea but it should solve your problem. Good Luck!!

    1G1G, Brad
    Attached Images Attached Images
    Last edited by aka brad; 06-24-2004 at 02:31 PM.

  9. #9
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    Does the chain fall to the inside or the outside? Guessing outside ... I suspect the PVC compresses under stress and accentuates the alignment problem. Replace the PVC with cog spacers from the cassette you massacred.

  10. #10
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    sounds like you're using an 1/8 inch chain? which the gurus say works fine "the wider the better", well it didn't work for me either. i never had a problem before or after i tried using this mis-match. stick with a 3/32 in. chain, that'll fix it!!



    Quote Originally Posted by liaudio
    OK.....
    here is my setup- 16t rear cassette cog from a shimano 8 speed cassette. Cog is in like new condition, not bent or worn. I'm using aluminum and steel cassette spacers from a few old cassettes and cut PVC pipe to space out the chainline. (which happens to be perfect. If its off, i dont know how the hell im gonna get the line any straighter!) I am using a brand new Deora 8/9 speed hub on a mavic 221 rim. Wheel is true, no proken spokes and spokes are properly tensioned. I have 2 tuggernuts, rear QR skewer, and RaceFace evolve DH cranks and BB. I dont have a singleator or anything like that. I noticed that the chainring was set oblong, so i loosened all the chainring bolts, spun the cranks a bunch, then slowly re-tightened them all.

    Before i went for a ride yesterday, i stopped into a shop that knows singlespeeds. He told me i needed a new chain, which i did because my 9speed compatible was a little twisted. I bought a Sram Single Speed chain. He told me "wider is better" I put it on w/ the same amount of links as before.

    I made sure that the chain had no slack. I tightened the tuggernuts to right before the point when you can't freely backspin the pedals because of resistance.

    OK, im all ready to go for a nice, slightly technical, slightly hilly 20 mile ride.

    First banked hill....

    Chain falls off the rear cog. F*&% POS!

    I tighten up the chain a little more.

    Same thing about 3 miles later. "F*&%!"

    I tighten it up a little more

    Repeat above for the rest of the ride...

    I didnt really tighten the chain to the point of where it doesnt backspin freely. I tightened it to where you could back spin the cranks about 1 rotation. But it seemed that it always fell off the rear, and tightening made it fall-off less often.

    In frustration, i devised a little concotion on the rear freewheel... Check it out. I havent ridden on it yet. Im hoping it will solve my problems.

    Here are some pictures.

  11. #11
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    Methinks it da cog.

    I would tend toward the cog as the issue. I have a very loose 8 speed chain, wobbly alignment (PVC with some spacers), and ramped Chainring.

    Just bought a $4 single 20T cog and not dropping the chain any more.

    good luck!
    Attached Images Attached Images

  12. #12
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    You guys.....'sniffle....sniffle'..... are the greatest.

    Im gonna try all of your suggestions.

    I do have to say that those guides i made worked awesome. Chain didnt fall off once. Its kinda wierd looking though so,

    Im gonna buy a non-ramped front and rear chainring and dump the pvc spacers in lieu of aluminum ones.


    The wheel is in the stays evenly, so i dont think its that.

    Boy....it sure is complicated to try and be simple.

    THANKS A MILLION!

  13. #13
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    Upon closer inspection

    Is that a fiber washer next to the PVC? Looks as weak as a sponge.
    Last edited by pacman; 06-25-2004 at 11:45 AM. Reason: typing

  14. #14
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    fiber?

    i dont quite understand what you mean. I have it as follows:

    PVC 1/2"
    aluminum 3/16"
    aluminum 3/16"
    steel 1/32"
    custom guide
    aluminum 3/16"
    16t cog
    pvc 1/4"
    aluminum 3/16"
    lock ring and washer

  15. #15
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    Gap?

    Just that there appears to be a gap between the PVC and hub filled by something grainy, maybe just dirt and grit?

  16. #16
    Rollin' a fatty Moderator
    Reputation: DiRt DeViL's Avatar
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    Is the PVC Schedule 40 or regular? I'm using 1 1/4" Sch40 PVC spacers without problems on my SS.

  17. #17
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    honestly....i bought the PVC spacer kit on ebay....its the "hollowpoint" something kit.....the cogs on REALLLLL tight... its not loose. no gaps

  18. #18
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    Quote Originally Posted by liaudio
    honestly....i bought the PVC spacer kit on ebay....its the "hollowpoint" something kit.....the cogs on REALLLLL tight... its not loose. no gaps
    nitpicking ...
    If the lock ring has bottomed out on the free hub the ring will feel tight but the cog can float.

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