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  1. #1
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    Could out of round chainring or cog cause chain drops?

    I'm pretty new to Single speeds so please excuse me if this has been covered before.
    So I recently built up a Single speed using a 30T MRP bling ring on XX1 crank and a 20 Tooth cog in the back.
    Today while out on a ride, towards the end of the ride, the chain started to drop. Probably happened about 4-5 times total. Each time I was pedaling through a somewhat bumpy section of trail on a slight incline.
    After I got home I looked at the bike and thought maybe the wheel had shifted forward while I was riding and so maybe the chain was loose.
    Anyway, to make a long story short, after messing around with it for a while, I realized that as I'm spinning the crank, there would be spots where the chain felt really loose and spots where it felt really tight. I guess either the bling ring or the cog must be out of round?
    The question I have is, if I'm pedaling and happen to hit a bump or dip while the chain is loose, would this cause the chain to drop?
    Any other possible reasons why this started happening towards the end of my ride?(I used the chainline math thread in the sticky to calculate my chainline already so I think my chainline is good).
    Any help would be greatly appreciated. TIA

  2. #2
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    Quote Originally Posted by pwu_1 View Post
    Anyway, to make a long story short, after messing around with it for a while, I realized that as I'm spinning the crank, there would be spots where the chain felt really loose and spots where it felt really tight.
    That is normal. The chain should be as taunt as possible but there were be points in your pedal stroke where the tension changes.

    Any other possible reasons why this started happening towards the end of my ride?(I used the chainline math thread in the sticky to calculate my chainline already so I think my chainline is good).
    Any help would be greatly appreciated. TIA
    How does you frame accomplish chain tension? EBB? Track ends? Sliders? Arm Tensioner?

  3. #3
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    Could out of round chainring or cog cause chain drops?

    The frame has horizontal sliders. So my chain drops are most likely caused by some thing else? Maybe my chainline math is off?
    Or since it has sliders maybe the wheel is somewhat cockeyed? I did try to eyeball it to make sure the wheel is straight when I initially installed the wheel

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    Quote Originally Posted by pwu_1 View Post
    The frame has horizontal sliders. So my chain drops are most likely caused by some thing else? Maybe my chainline math is off?
    Or since it has sliders maybe the wheel is somewhat cockeyed? I did try to eyeball it to make sure the wheel is straight when I initially installed the wheel
    Are they horizontal sliders or track ends?

    Horizontal sliders:



    track ends:



    Are you using lock nuts or quick release skewers?

  5. #5
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    Could out of round chainring or cog cause chain drops?

    Sorry it's track ends. I'm using a 135x12mm hub with a sun ringle step down axle
    http://www.sun-ringle.com/mtb/access...nversion-axle/

    Pretty sure the wheel didnt slip while I was riding

  6. #6
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    Could out of round chainring or cog cause chain drops?

    Using the lock nuts as shown on that link I posted above

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    Okay that axle is the problem. It's not going to cut it for the torque that SS riding puts on it and I'd bet that despite what you think- your rear wheel is slipping.

    I know because I ran the exact same axle set up on my previous SS. I used to run a standard axle that used a 15mm locking nut that secured into the frame, but then I tacoed my wheel and the LBS told me that what you had would totally work... It didn't.

    You'll need a nut tugger to keep the axle from slipping forward. Surly makes one but there are other brands. You'll still probably have headaches with the axle set up you have even with a nut tugger.

  8. #8
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    I think its possible. I've never had a two piece chainring that was perfectly round and some have been worse than others. You can minimize it by rotating the crank to the tightest spot, loosen the chainring bolts, and tap the chainring rearwards with a rubber mallet, then tighten the chainring bolts. Single piece chainring is best for SS imo.
    At what point did you decide you needed more than 1 gear?

  9. #9
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    Quote Originally Posted by michaelscott View Post
    You'll need a nut tugger to keep the axle from slipping forward. Surly makes one but there are other brands. You'll still probably have headaches with the axle set up you have even with a nut tugger.
    Definitely what michaelscott said ^^^. Yes an out-of-round ring could cause a drop, it wouldn't happen as frequently as you describe. With properly set tension, it would need a dynamic situation to drop off at all. Example: my magic-geared hardtail with just a small bit of slack in the chain; G-ed out of a tight berm and immediately got on the gas, causing the unloaded slack section of chain to hop right off my chainring, and me to skip off into a tree.

    On a different note, check your chainline as well. If you're not straight as an arrow, I'd suggest moving your cog position to help alleviate future wear problems.

  10. #10
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    Could out of round chainring or cog cause chain drops?

    I checked the chain line again and messed with it some more last night. I tried swapping out the crank and chainring to a different one but still got the tight/slack chain. That pretty much ruled out the chainring. Then I marked the rear cog and was able to get the chain to go tight or slack depending on where the mark was. So I guess the cog is out of round or slightly deformed or something. It's a pretty big difference. If I tension the wheel where the cog is the most slack then when it spins to the tight spot it almost feel like its binding and there is pretty much zero deflection on the chain.

    During my ride, seems like the chain would drop in medium speed,bumpy, slight up hill sections. I'm thinking its because I'm geared so low that in these situations when I'm almost spinning out the gear I'm not really applying much torque and if I hit a bump just right while the cog is on the low spot it would make it easy for the chain to drop.

    Anyway, I've been thinking about getting the lunar quick-change cog so this pretty much sealed the deal for me. Ordered the quick change cog today and will report back after I change it out.

  11. #11
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    Here's hoping that the cog you've been having problems with is a stamped cheapy and not any of the wide-base offerings we all love, otherwise the lack of roundness will be rather shocking. Your experience with pedaling cadence versus dropping makes perfect sense though.

    My fingers are crossed for your cog solution!

  12. #12
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    It is a origin8 torq lite cassette cog so not the cheapest but definitely not as nice as a Chris King or even a surly cog.

    But yeah, I'm hoping this new cog will solve my problem too.

  13. #13
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    Ok so I received the Lunar bikes "quick-cog" last week and installed it. The quick-cog fixed the tight/loose chain issue I was having with the other cog. Also, the tooth seems to be deeper so it makes it harder for the chain to jump off. It is actually a lot harder to get the chain off the cog when I'm trying to remove the wheel.
    So far I put about 50 miles on the bike using the quick-cog and so far haven't dropped the chain.

  14. #14
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    Oh those are so cool!!!!!

    I remember this system coming up in the forums a while back, and I never gave it much thought since I'm a strictly freewheel person these days. That being said, if you're willing to drop the coin, this is a damn cool solution:
    Lunar Bikes - Single Speed Cogs

    Please update with a picture of the cog, specifically the sides, when you get a few more miles on it. What you say about the chain coming off with more effort makes me think the profile of the cog might be a bit wide to start out with. Jump in if I'm off base though.


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    Could out of round chainring or cog cause chain drops?

    Quote Originally Posted by michaelscott View Post
    Are they horizontal sliders or track ends?

    Horizontal sliders:

    Wrong. Horizontal dropouts, but not sliders.



    These are sliding dropouts (one of many versions).
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  16. #16
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    Could out of round chainring or cog cause chain drops?

    Quote Originally Posted by ride_bikes View Post
    I think its possible. I've never had a two piece chainring that was perfectly round and some have been worse than others. You can minimize it by rotating the crank to the tightest spot, loosen the chainring bolts, and tap the chainring rearwards with a rubber mallet, then tighten the chainring bolts. Single piece chainring is best for SS imo.
    No need for the mallet. Just loosen the chainring bolts, squeeze the top and bottom runs of the chain together, then retighten the bolts before letting go.
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  17. #17
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    Quote Originally Posted by shiggy View Post
    Wrong. Horizontal dropouts, but not sliders.



    These are sliding dropouts (one of many versions).
    Doh. My bad. You are correct.

  18. #18
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    Quote Originally Posted by blackgriffen_1 View Post
    My fingers are crossed for your cog solution!
    Quote Originally Posted by pwu_1 View Post
    But yeah, I'm hoping this new cog will solve my problem too.
    I read these two comments out loud for my friend, he thought I was visiting a totally different forum..

  19. #19
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    If your chain tension is uneven, check out what Uncle Sheldon (RIP) had to say about it:

    Fixed Gear Bicycles for the Road

    "it IS possible that you are faster or slower than anybody else who is having at least as much if not more or less fun"

  20. #20
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    Just wanted to give another quick update. I got about 300 miles on the SS since putting the Lunar quick change cog on and haven't had a single chain drop. I had some issues with the wheel slipping in the track ends resulting in very loose chain tension. Even then I didn't get any chain drop.
    Really liking the quick-change cog. I hope the cog will last me a while. Might actually pick up some extra ones for spares in case they stop making them.

  21. #21
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    pwu_1,

    Great to hear our Quick Cogs working well for you. We probably have the deepest cog tooth out there which will allow a slack chain to stay seated even when bouncing around. I'm still riding on the same cog that I began testing with over a year ago and it is not showing any sign of wear.

  22. #22
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    TacoMan,

    Is 18t the smallest quick cog that'll fit with the driver? Is a 16t or 17t in the works?

  23. #23
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    18T is the smallest. Are you running a small chainring or just gearing for flats? I run a 22T cog, 32 ring, but all our rides out here have really steep climbs.

  24. #24
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    Quote Originally Posted by michaelscott View Post
    Are they horizontal sliders or track ends?


    Quote Originally Posted by shiggy View Post
    Wrong. Horizontal dropouts, but not sliders......

    Personally,...i've always thought of these to be "Semi- Horizontal" dropouts because they angle upwards more, and tend to be much shorter in length to a more practicle (for SS and fixed) longer horizontal droupout.

    The dropouts on my 1977 Schwill Paramount and 1988 or so Serotta are much longer, and angle up less.

    Here's the Serotta. (Axle all the way back,...i like all the wheelbase i can get for more comfort!)



    ....And the 1977 Schwinn Paramount. You don't see many current "road" bikes sporting braze on's for rack mounting, which is what i made use of here. Nice and long Campagnolo dropouts here, with not much up angle.
    Not sure if Campy even make these anymore???



    BTW, the Reynolds 532 tubing,very raked fork, and upright riding position make for a comfy fixed gear/SS grocery getter.



    (Seat was just put on for photo, now riding "level".

    Oh,....does a "MTN" Blackburn rear rack now make this bike appropriate for a MTB Forum?


    Last edited by joejeweler; 09-01-2013 at 05:05 PM.

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