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  1. #1
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    Small cog on SIR9... any luck? (chainslap)

    Hey guys,

    I have been running 32/15 for a while and recently switched from a monocog to a sir9. I have been getting chain slap on the underside of the chainstay when climbing and going over bumps. Now, it is pretty much a new chain still (100mi) and I keep tightening it after every ride so I am hoping once most of the stretch goes away this will stop. However, I don't want to run it so tight the cranks bind and I have seen another post on mtbr.com that seems to indicate I should run at least a 17t.

    I don't want to go up unless I have to... but I don't see the sense in damaging my frame in the meantime. Has anyone had any luck?

    Thanks

    P.S. I just centered the chainring a bit so maybe that will help me run it tighter without binding. I also noticed my surly cog on my stans hub has some play to it if I squeeze the chain... does that sound normal?

  2. #2
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    Just run a chainstay protector if you're worried. Chain slap isn't going to cause any issues, except paint chips.

  3. #3
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    what about a larger front chainring and cog combo? 35:17 or something?

    Quote Originally Posted by driver145 View Post
    I also noticed my surly cog on my stans hub has some play to it if I squeeze the chain... does that sound normal?
    Can you elaborate? Is the cog loose on the hub?

  4. #4
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    Quote Originally Posted by rob1035 View Post
    what about a larger front chainring and cog combo? 35:17 or something?

    Can you elaborate? Is the cog loose on the hub?
    I am running 36x15 on a 2010 SIR and there's no chain slappin goin on... didn't happen when I was running 34x15 either.

  5. #5
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    In regards to the cog play on the hub body, if I squeeze the chain tight I can see the cog move slightly. Maybe 1 mm. But it does make the chain slacker...

    Also, I think the chain is mostly hitting the braze-on which I could care less about. It's also hitting the frame slightly though which I don't want rusting. I was also wondering if hitting the braze on could damage the chain over time but I guess it's pretty slack when it hits so maybe not...

  6. #6
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    I've noticed my surly cog also shifts a bit on the freehub body. It causes a slackening in the chainline and tightening elsewhere. Usually, I find that I get one really tight spot and one loose spot from it. I thought I was going crazy as my chain tension will change a lot if I'm mashing hard, but it seems like this is the issue

    I haven't figured out how to stop it but I think it's caused by the splines being slightly different size than those on the hub.

    Certainly is annoying.

  7. #7
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    Sounds like the Surly cog tolerance is off slight from your freehub. FWIW, I run Endless cogs, and on most hubs they are perfectly fitted, and some hubs (i9 for sure), they are "tight" requiring a little file work.

  8. #8
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    I've been kicking myself a bit for not getting an endless cog for that very reason, but I was a bit concerned about how the aluminum cog would wear compared to steel. Perhaps the next one, I'll try endless.

  9. #9
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    Well thanks for the replies. I will keep playing with what I got for now.

    I would like to try another cog if this doesn't work but then again I might just be throwing money at an idea that won't pan out.

  10. #10
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    Got any pics of your chain?

  11. #11
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    Michaelscott: Not at the moment (on my phone).

    Also after the last ride it is now slack enough I need to remove a link and start over with the EBB (although on the monocog I would ride it like this or even much looser w/o concern) BTW I ran the EBB through its lower rather than upper range this whole time.

  12. #12
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    This is how it looks after my ride today (this is the loosest position in the pedal stroke). It was slapping today too. The EBB is maxed out (I can of course remove a link though and start over). Honestly though, I don't even like how tight it is. I can hear and feel the chain straining through part of the pedal stroke where it is tightest. Here is the big problem though; I can put my weight on the pedal and lift the chain up to the frame even at the tightest spot in the pedal stroke... so even if I get a better cog it won't solve this problem...

    Either I need to deal with it (with or without a protector) or go bigger...

    It sounds like people who got away with a 15t were running bigger chainrings which also makes you wonder what the application was in the first place and if chainslap would have ever been an issue. It only does it when I am mashing fast uphill over bumps and the rear tire starts hopping around... Like trying to get up a sudden steep climb full of roots as quickly as possible.

    Also, I am 185-190lbs, so that might be a factor...
    Attached Thumbnails Attached Thumbnails Small cog on SIR9... any luck? (chainslap)-img_0224.2.jpg  


  13. #13
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    Maybe a new chainring is in order? Might be the picture but that one looks a little worn...

    Weird symptoms for sure...

  14. #14
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    It is just dirty. I WD40'd it before I put it on this bike and it shows zero wear to my eyes. It is a surly stainless steel chainring. Also the taller than usual teeth make them look skinny.

    Edit: I just cleaned off a few teeth to take a better picture and they are showing some wear but doesn't seem that bad to me... although that is a fairly uneducated opinion.
    Attached Thumbnails Attached Thumbnails Small cog on SIR9... any luck? (chainslap)-img_0226.2.jpg  


  15. #15
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    That is strange dude. The chain looks plenty taunt. You only use the EBB to tension correct? Vertical dropouts?

  16. #16
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    So here is a (crappy) picture with me mashing on one of the pedals with brakes on. If you compare this to the other picture I posted the distance to the braze on has practically doubled... so if I hit a bump at the same time it makes sense the chain will come up and hit...

    I am tempted to knock off the braze-on and just go over it with touch up paint and then put a clear chainstay protector over the whole thing... will still be annoying though. A quiet ride is one of the perks of singlespeeding...
    Attached Thumbnails Attached Thumbnails Small cog on SIR9... any luck? (chainslap)-photo-1-.jpg  


  17. #17
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    I really think you'll be better off with a larger cog and chainring combo.

    However, that tension issue is really confounding....

  18. #18
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    It looks like chain stay curves over the top of the dropout area. Or maybe it is just the angle of the picture.

    Small cog on SIR9... any luck? (chainslap)-chainstay.jpg

    Is this where the contact is happening?

    From this angle it also looks like your chain has some slack to it.

    Like Rob and others have said- probably just need to run a larger cog

  19. #19
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    Re: Small cog on SIR9... any luck? (chainslap)

    My guess is that frame flex is the culprit and the solution is a bigger cog and chainring.

    I get a similar change in chain tension on the bottom part of the chain when I stand and crank on the pedals.

    Fwiw, I've heard a few bigger guys around here describe their SIR 9s as "noodly" . Not that it means much, but your issue could be an unholy combination of small gearing, a flexy-er frame, and monster legs....

    Sent from my DROID RAZR HD using Tapatalk 2
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  20. #20
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    I agree it can only be frame flex and larger cog/chain ring is really sort of a band-aid. I'd assume with that much frame flex there is a good chance that when it flexes enough and you hit a bump while mashing one of these days you're going to drop a chain...

    It may be worth contacting Niner about this. I have seen frames over the years that somehow skipped the heat tempering phase of the manufacturing process.

    Next alternative (not what you want to hear) would be to find another frame that is stiffer and won't have the same issues.

  21. #21
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    Quote Originally Posted by rideorange525 View Post
    Next alternative (not what you want to hear) would be to find another frame that is stiffer and won't have the same issues.
    Jones baby!

  22. #22
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    All frames flex, and the right amount of flex is a good thing- especially on a ridged SS. I think you just need to go with a bigger ring/cog combo and everything will be peachy.


    Quote Originally Posted by driver145 View Post
    Honestly though, I don't even like how tight it is. I can hear and feel the chain straining through part of the pedal stroke where it is tightest.
    Until you get this issue resolved I would just wrap something around the chainstay and set the chain at the correct tension and live with it. Running a chain that tight will ruin your hub and bb bearings, and also sap power.

  23. #23
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    Thanks for all the help guys.

    I am happy with the amount of flex the frame has. It is a little more flexy than the monocog but in a good way. I can make it 33/16 with parts I already have (by stealing them from my other bikes). I will try that and then I will know if I can get away with 34/16 or if I have to go with 36.
    Last edited by driver145; 07-05-2013 at 09:43 AM.

  24. #24
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    I was lazy and tried 32/16 instead of 33/16. It is much better but still hits in a few sections of my local trail (I would say its hitting about 20% of what it was before). I cannot decide what I want to do yet... so I guess I will try 33/16 now.

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