2009 Rig Varying Chain Tension- Mtbr.com
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  1. #1
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    2009 Rig Varying Chain Tension

    I've got a 2009 Fisher Rig that has the Bontrager Race Lite Singlespeed crank and the stock ekky-ekky EBB. Both the chainring (32t) and the cog (20t) are from Home Brewed Components. When I rotate the crank the chain tension is tightest if the non-drive-side crank arm is pointing forward. This happened with the original stuff and I got the HBC stuff in hopes it would go away. Does this mean the EBB is skewed or just plain bad -- either in how it sets in the frame or how it positions the bottom bracket? Or does it point to how the chainring attaches to the crank arm?

    Thanks...
    Remember, nobody knows. So let's find out...

  2. #2
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    Rig

    Quote Originally Posted by theGliberal
    I've got a 2009 Fisher Rig that has the Bontrager Race Lite Singlespeed crank and the stock ekky-ekky EBB. Both the chainring (32t) and the cog (20t) are from Home Brewed Components. When I rotate the crank the chain tension is tightest if the non-drive-side crank arm is pointing forward. This happened with the original stuff and I got the HBC stuff in hopes it would go away. Does this mean the EBB is skewed or just plain bad -- either in how it sets in the frame or how it positions the bottom bracket? Or does it point to how the chainring attaches to the crank arm?

    Thanks...
    This is the case with almost all drivetrains. It is from several factors. If it is not making your chain drop, I would not worry about it. Find a happy medium in the tension and roll! As for the EBB, I think they are a poor choice in engineering, but some really like them. To each his own I suppose.
    Cheers,
    C.

  3. #3
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    Is the ring centered on the crank arms? Sheldon Brown explains the process here.
    -- let's ride

  4. #4
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    The Sheldon Brown procedure references "stack bolts" and there aren't any -- a single lock ring on the inside of the chain ring holds it on to the crank. The four bolts that appear in a picture of the Rig are only for the bash plate.
    Remember, nobody knows. So let's find out...

  5. #5
    openwound
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    Oh, ok, so you've got a spiderless crank/ring. You might take a look at where the ring mates to the crank and see if there's any obvious sign of something causing the ring to not center.

    How bad is the tight spot? Or how loose is the loose spot? As has been asked, are you dropping the chain because of the variance in chain tension?

    If it's not so loose that you're dropping the chain, then a slight tight spot won't kill it.
    -- let's ride

  6. #6
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    The rings, front and rear may look round but they are not perfect. My 32t is 1/8" bigger in one direction than the other.

  7. #7
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    Quote Originally Posted by can't get right
    The rings, front and rear may look round but they are not perfect. My 32t is 1/8" bigger in one direction than the other.
    is yours an HBC ring?
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
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  8. #8
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    Quote Originally Posted by meltingfeather
    is yours an HBC ring?
    Nope, I tried to get one of his products but I have an awkward BCD.

    I hope he will chime in here and confirm that it is nearly impossible to make things exact.

  9. #9
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    I think the main problem is from the EBB. I used to have an '08 Rig and I hated the EBB since the day I got it. No matter how many times I cleaned it and torqued it, it still made noise and slipped. I think there is a lot of chances for error in the EBB. I have since switched to a Surly Karate Monkey and I have the same crankset as you. My tight spot is not horrible, but a tight spot is almost inevitable on all SS bikes.
    My motorcycle runs on infant blood

  10. #10
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    Thanks for the responses. I'm not dropping the chain, but try to adjust the tension regularly because the EBB slips. It would be interesting to see what ISAR says 'cuz he had the same Rig at one time.
    Remember, nobody knows. So let's find out...

  11. #11
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    Quote Originally Posted by can't get right
    Nope, I tried to get one of his products but I have an awkward BCD.
    yeah, the one-offs are 'spensive.
    Quote Originally Posted by can't get right
    I hope he will chime in here and confirm that it is nearly impossible to make things exact.
    Yeah, but that's kinda what CNC milling is about.
    from the home page:
    "These chainrings are fully CNC machined from high quality 7075-T6 aluminum and held to tight tolerances, producing a ROUND chainring."
    I'm hoping "tight" is better than 1/8" out of round... which seems like it could be easier to do with spiderless? maybe? anyone...? bueller?
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
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  12. #12
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    To the OP...

    Remove the chain, clean the chainring and then spin the cranks. Watch from above and you should be able to notice any eccentricity. You could even put a thick cable tie on the seat tube, level with the top of the chainring and cut it where it crosses the chainline to assist in finding the tight spot. Once you've done that, remove the chainring and clean the crank/chainring interface. Rotate the chainring 180 degrees then refit it to the crank. Measure again as above. Repeat if necessary, rotating the chainring by one spindle tooth at a time. Hope this helps.

    The EBB is only holding the bottom bracket in place, and shouldn't be causing the problem. The crank spindle might be ever so slightly bent as well.

    Do the same for the rear sprocket, for the freehub might be off a little, or the axle might be bent.
    I see hills.

    I want to climb them.

  13. #13
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    Okay, so I'm not the only one...

    Quote Originally Posted by Stevob
    To the OP...

    Rotate the chainring 180 degrees then refit it to the crank. Measure again as above. Repeat if necessary, rotating the chainring by one spindle tooth at a time. Hope this helps.

    Do the same for the rear sprocket, for the freehub might be off a little, or the axle might be bent.
    Steve,

    Good input. I too have wrestled with a tight spot. Went to Sheldon's Bible, and tried the above thinking the chainring was out of round. No EBB to complicate matters, and with paragon sliders, am able to micro adjust tension w/o issues.

    From what I can tell the WTB sprocket (cog) is the culprit. Have tried rotating it in relation to the cranks w/o luck. Feel that the tight spot is taking it's toll on bearings, pawls, and the entire driveline. [WTB sprockets now look identical to Origin 8's, so ?-able quality.]

    Should I be concerned enough to replace the sprocket, ignore it, or just be sure that the tight spot is not so tight as to bind?
    BTW Is 1/2" slack measured by total deflection, or one direction?
    Thanks, in advance for any valuable input. (Haters go for a ride - you'll feel better...)

  14. #14
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    Quote Originally Posted by Flyin'W
    Should I be concerned enough to replace the sprocket, ignore it, or just be sure that the tight spot is not so tight as to bind?
    BTW Is 1/2" slack measured by total deflection, or one direction?
    Things like that bug me, and WTB cogs aren't that great, so I'd invest in a new cog if it were my bike.
    That said, if your chain isn't jumping, it's not really a practical problem, just make sure that you're not binding.
    I go ~1/2" total, but i also just feel the chain through a couple of revolutions of the crank and make sure it's just loose enough to move freely. 1" of total play is too much for my tastes.
    Quote Originally Posted by Flyin'W
    Thanks, in advance for any valuable input. (Haters go for a ride - you'll feel better...)
    who's hating?
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
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  15. #15
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    MF,
    Thanks, for your reply.
    Will replace the WTB cog (sprocket) with another more reputable steel one (Surly, CK, or ?).

    RE: The haters comment was proactive for those ego-centric, e-bikers that plague this forum, causing many to not post. We all ride, input supports - flaming divides.

  16. #16
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    Kudos to you Flyin'W, for not starting a new thread.
    I see hills.

    I want to climb them.

  17. #17
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    so the cog is slightly off round (presumably) causing a slight tension when you turn the cranks by hand, and you're worried about it wearing out the hub.

    but you're not worried about the extreme torque exerted on the hub when you're standing and hammering on your singlespeed?

    uhhhhhhhhhhhhh

  18. #18
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    No,not worried about hub damage from SS mashing. Uneven chain tension is pronounced, and caused me to following Sheldon's guide, plus all tips in this thread without resolve.
    Yes, this causes me concern - hence my post.
    If I'm missing something, and you have useful input please contribute.

  19. #19
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    http://forums.mtbr.com/showpost.php?...0&postcount=17

    But if you're sure it's the cog, replace it.

    ...Though I've had good luck with WTB cogs. I actually prefer them because they have the wide base for extra support. The only other cogs I use are Shimano DX/DXR, which are very affordable ($10/ea).

  20. #20
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    Quote Originally Posted by alexrex20
    so the cog is slightly off round (presumably) causing a slight tension when you turn the cranks by hand, and you're worried about it wearing out the hub.

    but you're not worried about the extreme torque exerted on the hub when you're standing and hammering on your singlespeed?

    uhhhhhhhhhhhhh
    you might think you're quadzilla or something, but a binding chain will put MUCH more stress (many many times more) on all the components than the relatively small torque from pedaling.
    there is a misconception that SS bikes see large amounts of torque due to standing and mashing.
    geared bike hubs see much more torque due to the more favorable gearing.

    Flyin'W- now I see what you mean.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
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  21. #21
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    For a given force (on the pedals) at a given speed, a lower gear ratio (via a geared hub) will provide more torque. You're right that there is a misconception. There's also a misinterpretation of the physics. As the speed increases, the torque will decrease when either the pedal force or gear ratio decreases.

    At a given speed, a singlespeed bike with a taller ratio than a geared bike will be exerting more torque on the hub than the geared bike. So at slow speeds, the singlespeed bike will obviously need more torque to accelerate at the same rate to the same speed as the geared bike.

    Or I guess it wasn't so obvious... Nice try though.

  22. #22
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    It should be a simple concept. You can hand turn the crankarm past a binding chain link quite easily. Let's say you put 1lb of force on the crank arm which we can assume to be 175mm or 6.9in. That's 1.73lb-ft of force required and thus force exerted and experienced. On a 2:1 drivetrain that's 3.46lb-ft of centripetal force exerted on the hub.

    Now let's say you're on a steep hill at a slow speed, and you really need to stand and hammer. I weigh 185lb and run 2:1 gearing with 175mm crank arms. That's 644.5lb-ft of force being exerted onto the hub.

    That's 186 times more force from pedaling than from a binding chain, assuming a theoretical 1lb-ft of force required to turn past the bind. It would take a pretty ****ed up chain to equal that kind of force.

  23. #23
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    Quote Originally Posted by alexrex20
    At a given speed, a singlespeed bike with a taller ratio than a geared bike will be exerting more torque on the hub than the geared bike. So at slow speeds, the singlespeed bike will obviously need more torque to accelerate at the same rate to the same speed as the geared bike.

    Or I guess it wasn't so obvious... Nice try though.
    this is wrong. at a given speed both bikes will be exerting the same torque on the hub. that much should be very obvious.
    more chain tension? yes. more torque? no.
    geared bikes see higher peak torque due to the gearing, speed aside.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

  24. #24
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    Quote Originally Posted by alexrex20
    It should be a simple concept. You can hand turn the crankarm past a binding chain link quite easily. Let's say you put 1lb of force on the crank arm which we can assume to be 175mm or 6.9in. That's 1.73lb-ft of force required and thus force exerted and experienced. On a 2:1 drivetrain that's 3.46lb-ft of centripetal force exerted on the hub.

    Now let's say you're on a steep hill at a slow speed, and you really need to stand and hammer. I weigh 185lb and run 2:1 gearing with 175mm crank arms. That's 644.5lb-ft of force being exerted onto the hub.

    That's 186 times more force from pedaling than from a binding chain, assuming a theoretical 1lb-ft of force required to turn past the bind. It would take a pretty ****ed up chain to equal that kind of force.
    if you can turn the crankarm easily the chain is not binding.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

  25. #25
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    Quote Originally Posted by meltingfeather
    if you can turn the crankarm easily the chain is not binding.
    Wow.

  26. #26
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    Quote Originally Posted by meltingfeather
    this is wrong. at a given speed both bikes will be exerting the same torque on the hub. that much should be very obvious.
    Wrong. the wheel torque stays the same. The pedal torque changes and thus the force exerted on the hub.

  27. #27
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    Quote Originally Posted by alexrex20
    Wow.
    i know, right? so simple and your whole example is out the window.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

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  29. #29
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    Quote Originally Posted by alexrex20
    Wrong. the wheel torque stays the same. The pedal torque changes and thus the force exerted on the hub.
    you are changing your story. you said more torque on the hub (the hub is part of the wheel):
    Quote Originally Posted by alexrex20
    At a given speed, a singlespeed bike with a taller ratio than a geared bike will be exerting more torque on the hub than the geared bike
    this is just the derailment that the OP was hoping to avoid.
    sorry, Flyin'W... back on topic!!
    I'd replace the cog. What you "worry" about is your own business, and our friend here has his facts a bit mixed up anyway.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
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  30. #30
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    Quote Originally Posted by alexrex20
    For a given force (on the pedals) at a given speed, a lower gear ratio (via a geared hub) will provide more torque. You're right that there is a misconception. There's also a misinterpretation of the physics. As the speed increases, the torque will decrease when either the pedal force or gear ratio decreases.

    At a given speed, a singlespeed bike with a taller ratio than a geared bike will be exerting more torque on the hub than the geared bike. So at slow speeds, the singlespeed bike will obviously need more torque to accelerate at the same rate to the same speed as the geared bike.

    Or I guess it wasn't so obvious... Nice try though.
    ---
    AL20,

    While your efforts are appreciated, your theory is both confusing and ?-able.
    Case in point - When Shimano launched the 12-36 cassette they saw a rash of exploded freehubs, This was due to torque in the lowest gear on a 29er to be 1500' lbs, while with a 34t cog it was around 1200' lbs of torque. (from shimano tech docs)

    Shimano's issue pretty much negates the theory that riding SS puts more stress/torque or does more potential damage to the hub/freehub. Running a bombproof rear hub, on a new set of wheels that I'd rather not damage, and the rare errant popping sounds heard while NOT hammering has me examining all driveline aspects.

    Hey, it's Friday.. so, let's all get out there and ride!

  31. #31
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    Gliberal, do you have any new links in the chain? was there any slop between the hub and the cog? I don't remember what cog you have.
    There's tolerance for error on every part of the bike, which means it's a possibility the spline was not concentric to the spline in the crank arm. A slightly off bottom bracket spindle would do that as well. As will a not so perfect chain. It takes about .005" of runout to start seeing a decent change in chain tension, which is not a lot, especially when you take into account tolerance buildup of several mating parts.
    However, if you suspect it is the ring or cog, shoot me an email and i'd be happy to check it out and replace it for you if need be.

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