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  1. #1
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    problems with chain tension with chain ring.

    I just picked up a new Surly 32t chainring and cogs to go with it (along with a new sram 850 chain). While installing the chain ring and starting to tension the chain, the chain goes from loose to tight when I turn the crank. I can't believe that the new surly stuff could be bent from the factory and maybe I am doing something wrong. I am using a Truvativ Stylo crank and the 14 bcd chain ring. Please help me, I am getting mad over the new stuff being junk already!
    Spinnin' & Grinnin'

  2. #2
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    photos? sounds like you somehow installed your chainring off-center. is there any chance that your chain has a tight spot in it too?

  3. #3
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    What do you mean by "tight spot"? When I spin the crank, the chain goes from tight to loose so I think thats what you mean. I have loosened the crank bolts up and tried to make sure the chain ring is centered but I don't think that would be that hard to center up the chain ring.
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  4. #4
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    It really doesn't matter. It's damn near impossible to manufacture a perfectly round chainring/cog, so the changes in tension are to be expected. As long as it doesn't throw the chain, it's fine.
    Sometimes, I question the value of my content.

  5. #5
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    I agree on the perfection of the ring but this is starting to remind me of the old Shimano Biopace rings when they were ovalized on purpose. A round pedal stroke is better but does it matter all that much on a SS since your standing and spinning low cadence all the time?
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  6. #6
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    Like eric1245 said, if it doesn't throw the chain, leave it. It'll be cool. The bolt holes on the crank may be off centre too. Try removing the chainring and rotating it to a different position on the crank if it becomes a problem.
    I see hills.

    I want to climb them.

  7. #7
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    on the subject of "perfectly round" chainrings, how tight/loose does it get? are you starting with the chain upber-tight and then it drops so loose that the chain can fall off? if that's the case, yes, there's something wrong with the chainring. but if it gets tighter and looser as you spin it, that's expected. it's impossible to manufacture a perfectly round chainring.

    what I meant by tight spots in the chain is that sometimes a single chain pivot gets mushed and is too tight to move freely.

  8. #8
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    It's not too bad but worse than I expected. I will try what Stevob said and rotate the chainring on the crank.
    Spinnin' & Grinnin'

  9. #9
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    Hey Rad Rider
    I just bought a Surly 36T 110bcd and had the same problem. As I am new to the SS thing I adjusted the chain tension snug while my chain was in the loose position. Went for a ride and the chain broke a 100 yards down the road. After reading your thread I fixed the chain and tensioned it while chain was in tighter position. Just got back from a great ride with lots of hill climbs and chain was perfect. Now I know

    Straw
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  10. #10
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    Funny that I've never had this problem with Homebrewed rings.

  11. #11
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    Tonight I put on a Surly Cog in the rear and I fixed the problem!!!! The chain ring is not 100% perfect since you said they can't be made exact but my chain does not hop around like it did. Looks like it's gonna be a great weekend of racing now that I know my problem is fixed
    Spinnin' & Grinnin'

  12. #12
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    Quote Originally Posted by Rad Rider 415 View Post
    Tonight I put on a Surly Cog in the rear and I fixed the problem!!!! The chain ring is not 100% perfect since you said they can't be made exact but my chain does not hop around like it did. Looks like it's gonna be a great weekend of racing now that I know my problem is fixed
    Cool beans, yo. Now you gotta do the real version of "fixed." Coasting is for losers.
    Sometimes, I question the value of my content.

  13. #13
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    I have a Fixie road bike I built last winter.... Funny thing is the chain ring on that is 20 years old prob and works like new
    Spinnin' & Grinnin'

  14. #14
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    I've never seen a perfectly round ring. Remember that your rear cog or freewheel could be out also. If both front and rear are and they're synced then you have double the trouble. I've used all of these SS and or fixed and none are perfect. Campy, Smimano, SR, Salsa, Suntour, Spot, Stronglight, Sram, Blackspire, Race Face, Cooks, Synchros, Real, Kooka.ect..........

    From Sheldons site.

    Centering Chainwheels

    "Ideally, a singlespeed should have a frame with horizontal dropouts or track-style horizontal fork ends. With this type of frame, the chain tension is regulated by moving the rear axle back and forth in the fork ends. If the chain is too tight, the drive train will bind, perhaps only at one angle of the pedals (chainwheels are not usually perfectly concentric). It should be tight as it can be without binding. If the chain is too loose, it can fall off, usually at the most inconvenient possible time.
    Set the rear axle so that the chain pulls taut at the tightest part of the cranks' rotation. One at a time, loosen up each of the stack bolts, and tighten it back just finger tight. Spin the crank slowly and watch for the chain to get to its tightest point. Strike the taut chain lightly with a convenient tool to make the chainring move a bit on its spider. Then rotate the crank some more, finding the new tightest spot, and repeat as necessary.

    This takes a little bit of your hands' learning how hard to hit the chain, and how loose to set the stack bolts, but it is really quite easy to learn.

    Tighten up the stack bolts a bit and re-check. Tighten the stack bolts in a regular pattern, like the lug nuts on a car wheel. I start by tightening the bolt opposite the crank, then move clockwise 2 bolts (144 degrees), tighten that one, clockwise 2 more, and so on. Never tighten two neighboring bolts in a row. You may prefer to go counterclockwise, but try to get in the habit of always starting at the same place and always going the same way. This reduces the chances of accidentally missing a bolt.

    Once you have the chainrings centered and secured, adjust the position of the rear axle to make the chain as nearly tight as possible without binding. Notice how freely the drivetrain turns when the chain is too loose. That is how freely it should turn when you are done, but with as little chain droop as possible."
    Zip ties? Not on my bike!

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