SS conversion "skipping" - Any suggestions?- Mtbr.com
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  1. #1
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    SS conversion "skipping" - Any suggestions?

    I converted my Trek Crockett to SS. The setup is...

    FSA Energy Cross crankset
    Wolftooth Elliptical chainring (outer position)
    American Classic Hurricane 11sp wheel
    Surly Stainless Cog
    Paul Melvin tensioner
    KMC 10sp chain

    None of the parts are worn. The cog is lined up with the chainring, and the tensioner is lined up with the cog (with a bit of room for the pulleys to move in/out if necessary). The chain length is such that the tesioner pulleys are vertical. I was using the wheel when I had the bike geared, so I don't believe it's a freehub issue.

    It "skips" (momentarily loses tension & "clunks") whenever I apply anything above light power.

    I read somewhere that the Surly cogs don't play nicely with 10sp chains, so I switched to a Chris King cog. Same issue.

    Next, I switched back to the Surly cog with an 8sp chain. Same issue.

    That's when I ran out of time.

    The only other thing I can think to try is one of those crappy stamped steel cogs that come free with most conversion kits. That's not a long term solution, though.

    Ideally, I'd like to use the 10sp chain since it's higher quality and the retention with the chainring will be better. I'd also prefer a stainless cog for durability, and one with a wide base to reduce possible freehub damage.

    Any thoughts?

  2. #2
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    A guy on here had issues with surly cogs skipping with a melvin. I still can't figure out how the hell that works but could be the problem.

    I've got a Melvin on the way to use with a surly and it'll be interesting whether I have problems with it.

    How are you figuring chainline? It can be finicky if it's off a touch sometimes.

  3. #3
    Downcountry AF
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    +1 measure chainline.

    Post a pic of your tensioner.

    is the chain skipping on the cog or is the freehub skipping? are you sure?

    what size cog are you running?
    Rigid SS 29er
    SS 29+
    Fat Lefty
    SS cyclocross
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    Stop asking how much it weighs and just go ride it.

  4. #4
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    First I'd try a non-elliptical ring with that tensioner. Second a surly singulator in push up mode, done.

  5. #5
    Downcountry AF
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    ^ this is all speculation for now, but there's a lot of guys out there running oval chainrings on their SS's with no tensioner, myself included. unlikely the cause.

    I would guess the tensioner is not lined up properly, or the chainline is off. (total stab in the dark). second guess is your hub is messed up.
    Rigid SS 29er
    SS 29+
    Fat Lefty
    SS cyclocross
    Full Sus 29er (Yuck)

    Stop asking how much it weighs and just go ride it.

  6. #6
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    That paul tensioner is more than should be necessary, the heft is likely to get to move. I would also run without one first. But if the chainstay, chain combo wont allow for it, well....

  7. #7
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    I'm running 42x18. This is for gravel on a CX bike with vertical dropouts, so I need some sort of tensioner.

    I'm confident the freehub is OK. I've been using this same wheel geared up until the conversion, and it doesn't take much pressure (at all) to get it to skip. Certainly less than it saw on a normal geared ride

    The Melvin is designed for 2x1 with a 20T range. It should easily handle an elliptical ring.

    It's pretty easy to rotate the Melvin and see that's it's lined up with the cog. And it's designed with a little side-to side play, so it wouldn't need to be dead on. (It is though.)

    That leaves chainline... I used a string pulled tight on the side of the chainring to mark where the cog should be on the freehub, Maybe not the most scientific method... What's the best way to measure?
    .

  8. #8
    Downcountry AF
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    it all sounded good till you got to here

    Quote Originally Posted by The_Mickstar View Post
    That leaves chainline... I used a string pulled tight on the side of the chainring to mark where the cog should be on the freehub, Maybe not the most scientific method... What's the best way to measure?
    .
    measure to the center of the frame.

    All About Bicycle Chainline
    Rigid SS 29er
    SS 29+
    Fat Lefty
    SS cyclocross
    Full Sus 29er (Yuck)

    Stop asking how much it weighs and just go ride it.

  9. #9
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    Interesting problem. Let us know how it works out.
    I remember back in the dark ages, using elliptical gears with a freewheel and getting a lot of the same skipping, especially when you really torque the crank in a high gear (42X 16). In addition to distressing the chain line I think it was distorting the frame and chain stays. If you have enough gusto, you can move that chain line on some frames. At the same time the tensioner is attempting to do its job absorbing the extra chain length you just provided for a fraction of a second. The chain pressure decreases slightly (elliptical), chain line changes slightly, and chain to gear pressure increases (smaller lobe of the elliptical more mechanical advantage), and the tensioner (poor bastard) tries to pick up the slack at a greater chain tension.
    It may not be one of those issues but all of them at the same instant.
    I may be be full of BS as well, but, as I say, it is an interesting issue.
    Cheers

  10. #10
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    I measured the chainline and found it to be ~3mm off. I fixed that, but the issue remained. I also individually tried a stamped steel cog, different skewers, and loosening the tensioner fixing bolt slightly (it was somewhat difficult to rotate the entire tensioner off the stop on the hanger); all to no avail.

    The issue being related to frame flex is a possibility, I suppose. I can't imagine the frame flexing enough to cause skipping under such light pressure.

    At this point, I'm out of ideas. I suspect the tensioner. I just can't figure out why.

  11. #11
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    Have you tried shortening your chain? Shouldn't matter but I've read of people saying that they run their Melvin closer to horizontal than vertical.

  12. #12
    The perfessor
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    - check your linear alignment between chainring & cog; have had this problem before and every time is was the alignment.........
    Rigid 29er Ti SS
    KHS Solo One SE 29er
    29er SC Tallboy AL
    Paketa Magnesium Road Bike

  13. #13
    Downcountry AF
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    are you saying your chainring or cog was askew?

    in a vertical dropout frame how much can you do to correct that? same with the cranks, how would you adjust that?
    Rigid SS 29er
    SS 29+
    Fat Lefty
    SS cyclocross
    Full Sus 29er (Yuck)

    Stop asking how much it weighs and just go ride it.

  14. #14
    SS Pusher Man
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    I run a 2' level from the chainring back to the cog do determine chainline. Ensures that those 2 components are square to each other.
    Bicycles donít have motors or batteries.:nono:

    Ebikes are not bicycles :nono:

  15. #15
    The perfessor
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    Quote Originally Posted by mtnbikej View Post
    I run a 2' level from the chainring back to the cog do determine chainline. Ensures that those 2 components are square to each other.
    Gotta be sure you're square to the bike frame, too, check measurements from the frame's centerline.......
    Rigid 29er Ti SS
    KHS Solo One SE 29er
    29er SC Tallboy AL
    Paketa Magnesium Road Bike

  16. #16
    SS Pusher Man
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    Quote Originally Posted by mr_chrome View Post
    Gotta be sure you're square to the bike frame, too, check measurements from the frame's centerline.......
    As long as the cog and ring are square to each other......orientation to the frame is not as important. IME
    Bicycles donít have motors or batteries.:nono:

    Ebikes are not bicycles :nono:

  17. #17
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    Do you have sufficient chain wrap around the rear cog?
    SS conversion "skipping" - Any suggestions?-melvin_gallery_3.jpg

    I had a conversion skip because the rear cog didn't have enough wrap around the lower part.
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  18. #18
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    Just found out my conversion has the same exact problem but I'm using a derailleur as a tensioner. However I know my chainline is perfect.

    So I'll be interested to see what works.

  19. #19
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    I had the same issue on my '16 Giant XTC, geared 32x18. Turned out the chain was not grabbing onto enough teeth on the cog because of the angle of my Singleator.

    I plan to change up the gearing this week as close to the magic gear as I can find (34x19), and get rid of the Singleator once and for all!

  20. #20
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    Quote Originally Posted by ktaylor15 View Post
    I had the same issue on my '16 Giant XTC, geared 32x18. Turned out the chain was not grabbing onto enough teeth on the cog because of the angle of my Singleator.

    I plan to change up the gearing this week as close to the magic gear as I can find (34x19), and get rid of the Singleator once and for all!
    Change the spring to run in push-up mode, plenty of wrap

  21. #21
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    If you are going to be running SS a lot I'd ditch the Crockett. Maybe grab an RLT 9 or something else that can be run SS without all the hassle. Might seem expensive but once you factor in your time and frustration it may be the way to go.

    I know Paul makes good stuff but that Melvin looks like a torture device to me!

  22. #22
    SS Pusher Man
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    Quote Originally Posted by Matterhorn View Post
    If you are going to be running SS a lot I'd ditch the Crockett. Maybe grab an RLT 9 or something else that can be run SS without all the hassle. Might seem expensive but once you factor in your time and frustration it may be the way to go.

    I know Paul makes good stuff but that Melvin looks like a torture device to me!
    Also, part of the enjoyment of SS'ing is not having to have the chain go through all those pulleys.....that's why riding your geared bike in one gear doesn't have the same feel as a true SS.
    Bicycles donít have motors or batteries.:nono:

    Ebikes are not bicycles :nono:

  23. #23
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    Yeah, I'd say get rid of the Melvin and get a good fixed tensioner run in push up mode for maximum chain wrap.

  24. #24
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    Quote Originally Posted by socal_jack View Post
    Change the spring to run in push-up mode, plenty of wrap
    Yeah the thing about that frame is that is has asymmetrical chain stays. With my current chain ring the chain will hit the chain stay if the tensioner is pushed up.

    Sucks.

  25. #25
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    Quote Originally Posted by ktaylor15 View Post
    Yeah the thing about that frame is that is has asymmetrical chain stays. With my current chain ring the chain will hit the chain stay if the tensioner is pushed up.

    Sucks.
    So what new frame are you getting? Trek is a bunch of Crock(ett)!

    Actually that is a nice frameset and a couple dudes around here have theirs setup geared and really like it. I'm only pulling your chain (right off the cog!)

  26. #26
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    Quote Originally Posted by Matterhorn View Post
    So what new frame are you getting? Trek is a bunch of Crock(ett)!

    Actually that is a nice frameset and a couple dudes around here have theirs setup geared and really like it. I'm only pulling your chain (right off the cog!)
    You've got me confused with OP. I'm sticking with my XTC, I love that frame. I'm just putting off buying a new cassette so I thought I'd goof around with it SS.

  27. #27
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    Quote Originally Posted by ktaylor15 View Post
    You've got me confused with OP. I'm sticking with my XTC, I love that frame. I'm just putting off buying a new cassette so I thought I'd goof around with it SS.
    Gotcha. Giant Ecstasy is a hilarious bike name!

    Putting off buying a new cassette may be your new life. SS forever!

  28. #28
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    Quote Originally Posted by The_Mickstar View Post
    I measured the chainline and found it to be ~3mm off. I fixed that, but the issue remained. I also individually tried a stamped steel cog, different skewers, and loosening the tensioner fixing bolt slightly (it was somewhat difficult to rotate the entire tensioner off the stop on the hanger); all to no avail.

    The issue being related to frame flex is a possibility, I suppose. I can't imagine the frame flexing enough to cause skipping under such light pressure.

    At this point, I'm out of ideas. I suspect the tensioner. I just can't figure out why.

    Did you ever figure out this issue? Iím having similar problems with a pre-alternator dropout el mariachi Ti. I installed new surly 32 chainring; surly 20t cog, surly singleator and SRAM 9 speed chain. I have checked the derailleur hanger alignment and singleator wheel alignment multiple times, and switched it back and forth between pushing up and pulling down but it will still skip when I put any significant force on it. I have not measured chainline, but Iíve eyeballed it many times and it looks straight. As far as derailleur hanger alignment, when I eyeball it it looked pretty dang straight and Iíve used he derailleur hanger alignment tool as well.

    I am a fairly handy mechanic who has built my bikes and adjusted and installed derailleurs many times but I canít make this work. What a I missing.

  29. #29
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    Quote Originally Posted by rth009 View Post
    Did you ever figure out this issue?
    I didn't. Sorry. I finally gave up, converted my Crockett back to geared, and got an All City Nature Boy 853 for SS gravel racing.

    I did email Paul about it, and their only suggestion was to shorten the chain. :/

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