Severe chain skip on a brand new build- Mtbr.com
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  1. #1
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    Severe chain skip on a brand new build

    Hi guys, I'm new to SS and I've got some issues with my bike. Under just a slightly stronger load my chain skips heavily. Chain, sprocket and cog are brand new. Both sprocket and cog are SS specific with long teeth. I run 34/16 and have chain tensioner with the shortest possible chain length - there is no way to get more chain wrap. So where's the problem?

    Is it possible entire cog is skipping on a freehub?
    Severe chain skip on a brand new build-20171108_222415.jpg
    Severe chain skip on a brand new build-20171108_222426.jpg

  2. #2
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    You may have too little chain wrap around the cog, try running the spring opposite on your tensioner, also is that shimano hub new or is it old and used?

  3. #3
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    Hub is old, it has aroun 9k km on it. I'm not sure this tensioner can be set to push the chain upward.. I'll have to see.

  4. #4
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    You might look at the freehub it might be the culprit, some of those shimano freehubs prematurely gave up the ghost and start skipping.

  5. #5
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    That is not much chain-wrap, and using the tensioner in the push-up direction will most likely hit the chainstay. I think you will need to use a half-link if that is the shortest chain that fits. Hopefully you don't have a narrow-wide chainring.

    I've had good luck with the Gusset SLink half link. Are you using a KMC X8 chain? The 3/32" Slink can join with the X8 using the Missing Link I (7.3mm) or traditional 3/32" single speed master links.

  6. #6
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    As others have said, tensioner should be used in the push up position. Now, if you can find one, I highly recommend a Soulcraft Convert tensioner, but they are out of production. They can be found once in awhile on the used market. It doesn't rely on spring tension. It's indexed into place and super easy to install and adjust.
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  7. #7
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    An actual Surly brand Singleator tensioner which looks like your tensioner however is many times better can be setup for push-up mode with a included spring swap. Only downside is you need an 18mm cone wrench to do a proper install to set the spring preload. These type of tensioners tend to have some slop in the jockey wheel which adds to the problem when there's not enough chain wrap.

    The Gussett Slink half-link can help with the wrap, but you can run a shorter chain in push-up mode. Did you try magic gearing it?
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  8. #8
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    I see the problem: you forgor to remove teh reflectorz.

  9. #9
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    What chain are you using? If it's not compatible with the SS cog it won't fully seat when wrapped and it will skip really easily.
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  10. #10
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    Not enough chain wrap. Been there and done that. You can likely watch the chain jump if you ride and look back at your cog.

    Good luck!

  11. #11
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    Quote Originally Posted by *OneSpeed* View Post
    What chain are you using? If it's not compatible with the SS cog it won't fully seat when wrapped and it will skip really easily.
    KMC X9-73. Which do you suggest to get?

    But the more I think about it the more I'm sure it's the hub. There was skipping before on another frame even when I rode gears. Never payed much attention to it as I thought chain and cassette were worn out. But it didn't skip as often as now, this is unusable.

  12. #12
    Downcountry AF
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    Quote Originally Posted by blue_dragon View Post
    KMC X9-73. Which do you suggest to get?
    9 speed chain? I suspect your SS cogs are not compatible with a 9 speed chain. You will probably need a SS chain, or maybe an 8 speed will work?
    Rigid SS 29er
    SS 29+
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    Stop asking how much it weighs and just go ride it.

  13. #13
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    I'm also going with not enough chain wrap. I've used that same $8 tensioner with a SRAM SS chain and had problems trying to run anything with 16 teeth or less. IIRC, you can't run that tensioner to push upwards so you're pretty much stuck running a larger cog (...probably difficult for you since you're already on 34 at the front) or try running a magic gear setup.

    Of course all this assumes you've got a fully compatible chain and cog, your chainline is dialed, and your tensioner is aligned correctly. That cheap tensioner can be finicky but is fine after it's set up right.

  14. #14
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    Quote Originally Posted by blue_dragon View Post
    Hi guys, I'm new to SS and I've got some issues with my bike. Under just a slightly stronger load my chain skips heavily. Chain, sprocket and cog are brand new. Both sprocket and cog are SS specific with long teeth. I run 34/16 and have chain tensioner with the shortest possible chain length - there is no way to get more chain wrap. So where's the problem?

    Is it possible entire cog is skipping on a freehub?
    Click image for larger version. 

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    Click image for larger version. 

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    Not enough tension on the tensioner?

  15. #15
    EAT MORE GRIME
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    tensioner should push chain up to increase wrap, not down.


    that is the problem. chain is doing half the grab it is capable of,
    which is trivial for your legs to overcome

    shorten chain by 2 - 3 links, flip tension direction
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  16. #16
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    There are two main options for chain skip.

    1. The chain is riding up and jumping teeth. This can be caused by incompatible chain/ rings. Insufficient chain rap/retention spring. Worn out rings and chain.

    2. Your free hub is going bad and will skip under heavy load.

    To check for chain jump, hold the rear brake hard and stand on the pedals. See if the chain is riding up. Try and replicate the jump and if the chain stays locked to your cogs its the freehub.
    Making shit harder than it needs to be isn't awesome, it's just...harder.

  17. #17
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    Along with the suggestions above, make sure that you don't have a stiff link on your chain.

  18. #18
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    OK, here's the deal: chain wrap is the issue.

    At first, I was sure freehub was the problem but upon trying same setup with another wheel problem persisted.

    So I improvised push-up tension with a zip-tie just to see what happens. It worked perfectly (chain skip resolved) but chainstay prevents tensioner from reaching position needed to tension the chain properly. Even if it did went further up chain would rub on the bottom side of the chainstay! See images below. I tried removing another link from chain but then it is several mm too short to connect. Damn!
    Severe chain skip on a brand new build-20171111_135320.jpg
    Severe chain skip on a brand new build-20171111_135329.jpg

    So I installed a segment of my old cassette with 14-16-18-21 teeth combo. Using 16 teeth chain skipped like crazy. Already at 18T there was no problem whatsoever even with downward pointing tensioner.
    Severe chain skip on a brand new build-20171111_145118.jpg

    So it basically comes down to this: 34-16 drivetrain is not usable on this frame. This particular combination of chainstay length and 34-16 teeth requires chain length which doesn't work with tensioner pointing down and there is no room for tensioner pointing upward. What are the chances of this happening?

    My next step is to buy bigger cog and chain ring to get more chain wrap. I will buy them as big as possible while maintaining this gear ratio which seems as the perfect one for me. 42/20, 44/21 will probably do the trick. I will also try to get a good upward tensioner as an extra precaution step.

  19. #19
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    if that amount of gear-inches works for you, also try 36-17 or 38-18. going bigger than 38 means you start running into potential ground clearance issues. i know that it was not that long ago that triple cranksets with 44t chainrings were common, but people bashed those on rocks all the time.

    what is the actual chainstay length on your frame? plug that in here an see what will get you closer.

    as has been pointed out, 34/16 is a pretty friggin steep gear. that's what i would use for gravel road races, never trails. 34/17 would be like taking a half-link out of your chain and probably be enough.

  20. #20
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    Chainstay is 425mm.

    I've set it up with old parts this afternoon: 44 big ring and 21T in the back (from old cassette) + my old chain. Just came back from 40km ride, no chain skipping. Not ideal as this combo is worn out and chainline is not perfect but I'll ride it until I figure exactly what teeth combo to buy. Also, winter is almost here and I don't ride as much during winter, I have time to think this through.

    Tnx everyone for feedback

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