Issues getting perfect tension ...- Mtbr.com
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  1. #1
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    Issues getting perfect tension ...

    Hey guys,

    Just recently converted my karate monkey to a SS. Loving it, prolly been on 6 rides now. First ride I had issues with the wheel sliding forward in the dropouts so picked up a surly chain tug and dialed in the tension and the wheel never moves! The tension that I setup was probably less than an inch slack. First ride with the tensioner, I found out after a bunch of cranking that the chain was binding up. Took a look at sheldons site and read that the chain will be tighter in different orientations of the crank as the chain ring is not symmetric? So ok, I saw this for my self while turning the crank slowly and watching the chain bind up in just one spot! So, loosened the tug a 1/2 turn or so. Now the slack seems a bit more then an 1 inch (moving the chain up and down).

    Next ride I threw the chain on a high torque climb and was like wtf, and put the chain back on. Didn't have another issue the rest of the ride though!

    I decided that maybe this is the slack that I need and went for another ride the other day. Again, in another high torque climb I threw the chain. So, I flipped the bike over and turned the adjuster in 1/2 turn. Later in the climb noticed a funky noise on the up crank of the right crank arm. So I thought maybe pedal noise. But after getting annoyed more I investigated. Turns out chain was binding up again.

    So, what I noticed was with my foot on the crank with very light weight, the chain tightened up all the slack. It almost looked like the chain was twisting a bit with the torque.

    So what gives? Does my steel frame just have so much flex that I need to run this chain with considerable slack and have to deal with throwing my chain? Or possibly there is a sweet spot where the chain isn't going to throw, and not bind? It looks like a very narrow sweet spot then.

    The chain line looks pretty dam perfect to me when looking at the line from behind the cog towards the crank. Advice? Thanks!


    Bike setup:

    crank: stock stylo 1.1 gxp
    rear cog: surly bmx
    chain: sram single speed

  2. #2
    AZ
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    Find the tight spot , loosen the chainring bolts , tap chainring to loosen tension a bit , retighten bolts and test . You might have to do it a couple of times . There is almost always a tight spot , this helps even out tension as the crankset makes a revolution .

  3. #3
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    Interesting, I'll have to try that, thanks.

  4. #4
    Out spokin'
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    An inch of up & down slack in the chain? That's way freakin' too slack. Maybe I don't understand. You said the chain "binds up"? How. Sorry, I've had a pint or two... I'm not following exactly what is going on. But you chain tension doesn't need to be "perfect" to work perfectly well.

    --Sparty
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  5. #5
    Ride Responsibly
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    What are you running for a front chain ring?
    Even after loosening and tapping the ring to center it, you will still have tight spots, hard to be perfect.

  6. #6
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    LWright:

    I'm running the default stylo 1.1 32t chainring in front. I'm starting to think I may change out this single speed chain for something else. I noticed on the ride this weekend that the chain was twisting in towards the frame when it was on the bottom (on the way back towards the cog).

    Sparticus: yes, when im in the middle between the cog and the chain ring and i move it in the vertical position, there is probably a 1 inch slack. But even with this slack it binds up.

  7. #7
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    Park recommends .5" up and .5" down - so I think he is good there.

    Try the positioning of the chainring thing- if that doesn't work, get a chainring you know will be round (a single speed machined one is best... I recommend Homebrewed components)

    Are you using a 1/8" chain on 3/32" cogs? That should be fine, but might be what is causing the "twisting" - since it would be wider than the cogs.

  8. #8
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    Sounds messed up to bind with 1" of slack as you describe it. Is your chainline really bad? Maybe chainline is marginal and further thrown off by frame flex?

  9. #9
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    naister: yes, it's a 3/32" on 1/8" chain. I'm thinking I may try a new 9 speed chain I have laying around, will that work? I know a 8 speed chain will work from what I hear.

  10. #10
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    This frame seems to flex like crazy! The chain will be totally slacky, and I'll go to put my foot on the pedal with light pressure, and the chain binds up (all the slack is gone). I'll take another look and see if I can adjust spacers to get any better. The chain line looks dam straight tho.

    It's just crazy, I threw the chain 5 or 6 times this last ride and the chain had tons of slack ...

  11. #11
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    either your chain line is way off, your ring, spider, or spindle is bent, or your ring isn't round. chances are your ring isn't round. loosen all four bolts just enough so can still move it by pulling the chain together towards your chain stay. spin your cranks slowly back wards till you hit the spot, pull chain slighty so the ring moves a bit inwards on the ring bolts, spin more, try again, etc. you can spend the rest of your life trying, but it will never be perfect.

    unless you pony up and buy good SS rings, cogs, and chains =D

  12. #12
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    Quote Originally Posted by phlite
    This frame seems to flex like crazy! The chain will be totally slacky, and I'll go to put my foot on the pedal with light pressure, and the chain binds up (all the slack is gone). I'll take another look and see if I can adjust spacers to get any better. The chain line looks dam straight tho.

    It's just crazy, I threw the chain 5 or 6 times this last ride and the chain had tons of slack ...
    Everyone seems to be ignoring the flexy frame part. This has me concerned. If pressure on the pedal causes the chain to tighten from the top portion of the cog to the top portion of the chainring, resulting in a very slacky chain under the rings, then that is physics and normal. If however, the chain, top and bottom tightens up, then you have a problem. My first guess would be a blown bottom bracket; grab you crankarms and lever them back and forth and check for play in the bottom bracket (any play at all means it's time for a new BB). I had a similar problem and this was the cause. You should not have more that 1/2" top and bottom play in the chain. Anymore and, as you experienced, you'll keep losing your chain. The alternative would be a cracked frame, but I'm thinking BB..
    Just one more rep and I get the toaster!

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