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  1. #1
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    My new love... but she has an really irritating flaw - need some guidance

    Hey guys,
    Ive been reading these threads for a while and have finally almost completed my first SS MTB build.
    Itís a KHS solo one frame,
    With some velocity blunt rims.

    My new love... but she has an really irritating flaw  - need some guidance-img_2464.jpg

    While the bike is amazing to ride I am have one catastrophic issue that is really spoiling the experience.

    Issue
    I canít keep the chain on when I climbÖ
    To qualify that itís when I have to stand stomp the pedals, that the chain derails. If I keep a steady power or a smooth stroke I generally donít have a problem.

    my drive chain consists of the following Holzfella cranks, chain ring (need to get something a little better) Sram PC1 chain and Velosolo 18t rear cog.

    Observation
    From what I can tell there is quiet a bit or lateral flex in the frame. To the point that you can visually see the chain get slack and tight as you peddle, ( I had my GF take it for a ride so I watch the chain)

    What I have checked so far:
    I have checked the chain line again and again
    Iíve played with the chain tension.
    My new love... but she has an really irritating flaw  - need some guidance-img_2493.jpg


    What am I doing wrong?
    getting really frustrated

  2. #2
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    ..you need the unspoken word here in ss..chain guide..sandwich, tensioner or otherwise..so sorry..
    lean forward

  3. #3
    AZ
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    Correct the chain line, its hard to tell from the pic but I'll bet its off. See this thread for some great tips to get it setup correctly:

    CHAINLINE math

  4. #4
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    mmm i did try the measurement method and its with in 1mm.
    I really like the look of the skewer test and i might be able to hone the issue with that.

    other wise... the surly singlator will have to come off the commuter. that would be a real shame as its a SS frame. :S

  5. #5
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    Is the chain line determined when pushing down on pedal or when unloaded? It sounds like the chain line is changing with varying pedal force.

    Its okay to use a tensioner.

    One can also use a nutted rear axle with that xt hub.
    lean forward

  6. #6
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    A couple of things...

    The cog is not sitting in the centre of the chain. Good indicator that the chainline is off.

    You have a flexy steel frame. Chain drops will happen. Consult your girlfriend to see if it's ok with you slamming your nuts against the stem every ride.

    Are you able to move your sliders forward enough to remove a full chain link? You don't seem to have enough tension on there either.

    I can't tell what brand of rear sprocket you're using. If it's a cheapy, replace it with something like a surly, with taller teeth. That usually helps a lot.

    Good luck!
    I see hills.

    I want to climb them.

  7. #7
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    unloaded, as its up in the stand when i am checking the chain line.

    when my 55kg GF was riding it i could see the chain going slack probably about 30mm of play from about 10mm when unloaded

  8. #8
    Nouveau Retrogrouch SuperModerator
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    My new love... but she has an really irritating flaw - need some guidance

    Quote Originally Posted by 1niceride View Post
    Is the chain line determined when pushing down on pedal or when unloaded? It sounds like the chain line is changing with varying pedal force.

    Its okay to use a tensioner.

    One can also use a nutted rear axle with that xt hub.
    Chainline does not change with pedal pressure unless you are getting HUGE lateral flex (unlikely).

    Tough to tell from the pic but I think you need to move the cog outboard a bit.
    mtbtires.com
    The trouble with common sense is it is no longer common

  9. #9
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    first of all thanks for all the advise guys, amazing response.

    Stevo, GF said is was ok as long as she was on the ride with me... she didnt want a miss a moment to point and laugh.

    there is quiet a bit of room in the sliders. but im pretty sure the chain tension is right.

    it a super star componet rear cog
    Name:  !BbI!)Z!B2k~$(KGrHqIH-EYEquE3g54eBKuizKz9Mw~~_1.JPG
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    i will have another look at the chain line and see how many microns im out :P

  10. #10
    one chain loop
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    chain usually derails at the cog and very seldom at the front. is it derailing inwards toward the wheel or out? usually the easiest solution is to move the cog few mm to where the chain is falling.
    everything sucks but my vacuum cleaner.

  11. #11
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    Quote Originally Posted by shiggy View Post
    Chainline does not change with pedal pressure unless you are getting HUGE lateral flex (unlikely).
    No, but the axle and crank are no longer parallel. That causes chain slack at the bottom that swings back and forth causing derailment.

    How about a sandwich guide in the rear. Its not a tensioner.. and they look okay..
    lean forward

  12. #12
    one chain loop
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    another advice is to use 3/32 chain since you have a 3/32 drivetrain. 1/8 chains doesn't bend laterally as much as 3/32 does so it is not as good on flexy frames.
    everything sucks but my vacuum cleaner.

  13. #13
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    My new love... but she has an really irritating flaw - need some guidance

    When I get home (might not be tonight) ill give it another check and move it out a few more mm.
    Apart form this little issue I'm loving the move to a 29er SS
    It's so smooth and quiet and it just rolls over ****.
    Apart from that trench on the Yarra tails.
    Gf watched me go clean over the bars.
    A mate helped me up cause she was to busy laughing.

  14. #14
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    My new love... but she has an really irritating flaw - need some guidance

    That's an interesting thought fishcreek

  15. #15
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    Quote Originally Posted by fishcreek View Post
    another advice is to use 3/32 chain since you have a 3/32 drivetrain. 1/8 chains doesn't bend laterally as much as 3/32 does so it is not as good on flexy frames.
    This. When I look at the picture, that's not the right sized chain for that rear cog. I've ridden like that before in a pinch, which is to say I broke a chain, and the only one I could get my grubby paws on right that second was too large - but you couldn't pay me to do it on a regular basis. Start by getting the right size chain.

  16. #16
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    Quote Originally Posted by Edmuggles View Post
    Hey guys,
    Ive been reading these threads for a while and have finally almost completed my first SS MTB build.
    Itís a KHS solo one frame,
    With some velocity blunt rims.

    Click image for larger version. 

Name:	IMG_2464.jpg 
Views:	397 
Size:	118.3 KB 
ID:	816603

    While the bike is amazing to ride I am have one catastrophic issue that is really spoiling the experience.

    Issue
    I canít keep the chain on whe Also "n I climbÖ
    To qualify that itís when I have to stand stomp the pedals, that the chain derails. If I keep a steady power or a smooth stroke I generally donít have a problem.
    Take a look at your chainstays and downtube. From the photo they look undersized. If the chainstays are also dented for tire clearance that could be your problem. Flex in the chainstays could be causing the chain to jump.

    IMHO a lot of steel bikes are built with tubes that are undersized for "super sized" riders. This frames might work well for light guys but if you are above 160 pounds the frame should be using oversized tubing for stiffness. Riders above 200 pounds especially need stiffness in the BB area.

    Normal steel chainstays are oval with around 18mm cross section. The tall part of the oval can be 30mm but drive train stiffness comes mostly from the horizontal cross section so on most bikes you have the 18mm stays cross section.

    Some frames have areas where the chainstays are dented for extra tire clearance this can take the 18mm cross section down to around 12mm. The extra tire clearance can be nice but not if the result is horizontal flex.

    For single speed, you really want to have super stiff chainstay especially in the horizontal plane. It is also good to have a beefy down tube. Since single speeds run only one ring up front generally it is possible to build the frame without denting the chainstays so you get the full 18mm cross section for stiffness. For most riders, 18mm chainstays and 36mm downtubes are the way to go. Larger or stronger riders should consider have 38mm downtubes and 22mm round chainstays to bring stiffness to the BB area. Also "hooded" style dropouts help make the rear end stiffer compared to "plate" style.

    The good news is that if you up size your ring and cog to something like 38/22 the extra teeth will keep the chain from jumping even if the frame is flexing. With the extra teeth the chain will generally not jump when the frame flexes. The flex is still not good but with more teeth you should be able to prevent the chain from jumping.
    Last edited by febikes; 07-17-2013 at 07:48 AM.
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  17. #17
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    i bet a narrower chain will fix your issues. but if it doesn't...

    people are correct; you can figure out your problem in more detail by noting how the chain derails when it does (in front or in back; to the inside or outside).then you can adjust chainline accordingly.

  18. #18
    Beer Drnkr w/bike problem
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    If the problem still persist after trying some of the tricks above I would say get rid of the cog and get a Surly. I am not familiar with Velosolo cogs but from the picture they look a little flimsy. On my 1st SS I was using a torn apart Shimano cogs and always had issues, as soon as I got the Surly it never happened again. It could be that simple, maybe barrow one and try it.
    "Not drinking is the Single Speed World Championships version of doping" -Jacquie Phelan

  19. #19
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    Quote Originally Posted by TacoBeer View Post
    If the problem still persist after trying some of the tricks above I would say get rid of the cog and get a Surly. I am not familiar with Velosolo cogs but from the picture they look a little flimsy. On my 1st SS I was using a torn apart Shimano cogs and always had issues, as soon as I got the Surly it never happened again. It could be that simple, maybe barrow one and try it.
    This in addition to incorrect chainline.

    EDIT: As somebody said it looks like 1/8 inch chain on 3/32" cogs, fix that too and post back.
    Last edited by Natedogz; 07-17-2013 at 04:52 PM.
    Fat, drunk, and stupid is no way to go through life son...

  20. #20
    nothing to see here
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    Quote Originally Posted by TacoBeer View Post
    If the problem still persist after trying some of the tricks above I would say get rid of the cog and get a Surly. I am not familiar with Velosolo cogs but from the picture they look a little flimsy. On my 1st SS I was using a torn apart Shimano cogs and always had issues, as soon as I got the Surly it never happened again. It could be that simple, maybe barrow one and try it.
    The velosolo cog I bought got swapped for a Surly after just one ride. The cog wasn't round and that causes extra slack in the drivetrain for every revolution. I'd bet that is Ed's problem. Get a Surly sprocket with taller, better shaped teeth and a 9sp chain, fix the chainline and ride into the sunset with your GF.
    I see hills.

    I want to climb them.

  21. #21
    CB2
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    and now for something completely different...

    The only time I had a problem with dropping a chain it was the crank / bb combo I was using. I drank the koolaid and bought a very popular ss crank and bb combo.
    I guess my massive 135 pounds was too much for it and would flex it enough to throw the chain at the worst possible moment. Went back to XT and everything was all good again.

  22. #22
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    Quote Originally Posted by Edmuggles View Post
    when my 55kg GF was riding it i could see the chain going slack probably about 30mm of play from about 10mm when unloaded
    Turn the cranks backwards by hand and see how much the slack in the chain varies. If it still changes then it isn't frame flex, either the chainring or rear sprocket is off-centre.

  23. #23
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    Cog looks too far outboard to me, plus the chain is much wider than the cog, plus the teeth shape on that cog doesn't look very good.

    I ride a pretty flexy MonoCog Flight. Even when my chainline was off by 5mm I never dropped a chain except for when I had some cheap stamped steel cogs on it. Get a better cog and a 9spd chain, double check that chainline, and you'll be fine.

  24. #24
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    Quote Originally Posted by fishcreek View Post
    another advice is to use 3/32 chain since you have a 3/32 drivetrain. 1/8 chains doesn't bend laterally as much as 3/32 does so it is not as good on flexy frames.
    What he said.

  25. #25
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    When comparing where your sprocket teeth fall into your chain, it does look like your chainline is off. Move the sprocket outboard. Here is my chainline and yours for comparison. You will see how your teeth are rubbing against the side plates of the chain. Mine is directly centered on the rollers.




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