Middleburn Chainring Interference- Mtbr.com
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  1. #1
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    Middleburn Chainring Interference

    It seems that I can't run a 32t outer ring on a Middleburn dual spider since the crank arm gets in the way. Does anybody know if a 34t will fit or if I'll have to go as big as 36t? I was trying to set up a 32/30 double double driveline.
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  2. #2
    one chain loop
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    is it just me or is the spider mounted on backwards?
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  3. #3
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    Just you. The Middleburn spider kind of wraps around the crank arm. There is a relieved section where the arm lays. It's correct, maybe the angle of the pics make it look funny.

  4. #4
    one chain loop
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    sorry. hope someone can help you out.
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  5. #5
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    Maybe you should shift the spider around one spline.
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  6. #6
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    Quote Originally Posted by Velobike
    Maybe you should shift the spider around one spline.
    How would that help?

  7. #7
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    In the pic it looks like the lug on the chainring is touching the crank arm. Moving the spider by one spline would stop that.
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  8. #8
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    Quote Originally Posted by Velobike
    In the pic it looks like the lug on the chainring is touching the crank arm. Moving the spider by one spline would stop that.
    I see what you are saying. The lug is right next to the crank arm. There is a depression where the arm meets the spider so there is really only one way to mount the arm. I've come to the conclusion that I'll try a 34t ring since the diameter of the ring is the main problem. I'm just hoping I don't have to go all the way to a 36t. I might have to get the triple spider and put the 32 on the middle position and then find a 30t for the granny mounting location.

  9. #9
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    Can you bevel the edge of the ring for more clearance? I really can't see the problem too clearly. It doesn't look to be rubbing too much.

    He isn't saying to rotate the spider. Rotate the ring on the spider. Many rings have a little nubby that indicates how to assemble them. You put all the ring's nubbies in the same orientation, and typically you put them behind the arm to hide them. This is to get all the shifting stuff working together.

  10. #10
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    Quote Originally Posted by Hairllama
    It seems that I can't run a 32t outer ring on a Middleburn dual spider since the crank arm gets in the way. Does anybody know if a 34t will fit or if I'll have to go as big as 36t? I was trying to set up a 32/30 double double driveline.
    File the ring slightly so that it clears the crankarm. It'll work and nothing will implode.
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  11. #11
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    Quote Originally Posted by Drevil
    File the ring slightly so that it clears the crankarm. It'll work and nothing will implode.
    I did that on an old steel ring that was thinner. It almost fits, but then the chain catches on the crank arm. Part of the problem is the shape of the spider, the other problem is the shape of the crank arm. I'd never worked with Middleburn stuff before. It's cool, but has a few compatibility issues. I'll snap some more pics later today to try to illustrate things better.

  12. #12
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    Quote Originally Posted by Schmucker
    You put all the ring's nubbies in the same orientation, and typically you put them behind the arm to hide them. This is to get all the shifting stuff working together.
    I know what you are talking about with regard to ramps and pins. The ring I'm using is the same all the way around, it's a SS ring. There won't be any derailleurs on this bike to do any shifting.

  13. #13
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    I have attached a photo of my spare Middleburn cranks and spiders.

    The 5 arm is positioned as it would fit on the adjacent crank. It should fit without interference problems from a chainring.

    Sorry, I couldn't find the tool to take off the 4 arm so I could demonstrate it with the 5 arm on.
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  14. #14
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    Quote Originally Posted by Velobike
    It should fit without interference problems from a chainring.
    Have you tried it with a 32t chainring?

    Thanks for the pics, mine are coming shortly.

  15. #15
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    Here are more pics of the issue.
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  16. #16
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    And one more

    And one more
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  17. #17
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    Quote Originally Posted by Hairllama
    I know what you are talking about with regard to ramps and pins. The ring I'm using is the same all the way around, it's a SS ring. There won't be any derailleurs on this bike to do any shifting.
    Obviously, this is the SS forum and you said you were setting up a dingle. SS rings still may come with the nubby. I know my Blackspire has one. You can see it pretty clearly here.
    http://images.channeladvisor.com/Sel...oce,%20110.jpg
    It is right under 11034.

    Anyways, now that you've posted pics, it can be seen that you have Spot ring. They don't have the nubby. Your only solution is to increase the chainring size unless you want to try filing some grooves to clear the arm. They would have to be pretty deep and will probably result in chainring failure.

  18. #18
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    I see the nubby. Can't say I've noticed that before on any SS rings.

  19. #19
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    Something definitely looks wrong with that spider. Or you are missing some kind of spider spacer maybe. I don't own any Middleburns. I would just email them pics, or if in the US contact the owner of mtbtandems.com.

  20. #20
    HHL
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    not the spider's fault

    It just wasn't designed to take a chainring that small on that side of the spider.
    Measure twice, buy once. What I'm saying is, you have to be willing to ask a lot of questions concerning the desired result before buying, no matter how long it takes.

  21. #21
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    I just can't find anything in Middleburn's support materials that lists a minimum chainring size. I'm waiting to hear back from them. I have a suspicion that even 34t is too small.

  22. #22
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    Got enough room to have some sort of spacer between the arm and the spider, and still have enough thread angagement for the lockring?

    I'd almost be inclined to notch the two spots on the backside of the arm where the ring would need the clearance.

    Maybe some combo of those two things and trimming the ring down? Upsize all you rings and you rear cog to maintain your gearing, or have to get another crankset it looks like.
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  23. #23
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    Quote Originally Posted by scrublover
    Got enough room to have some sort of spacer between the arm and the spider, and still have enough thread angagement for the lockring?

    I'd almost be inclined to notch the two spots on the backside of the arm where the ring would need the clearance.

    Maybe some combo of those two things and trimming the ring down? Upsize all you rings and you rear cog to maintain your gearing, or have to get another crankset it looks like.
    I thought about notching the arm, but didn't really want to start grinding so soon. Even if there was a way to make a 32t fit, the arm would catch the chain since the clearance is so tight. I'll upsize to a 34t and see what happens. Questions emailed to Middleburn and MTB Tandems have gone unanswered. I thought about the spacer idea, but there really isn't enough room for a spacer at all.

  24. #24
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    Quote Originally Posted by Hairllama
    I thought about notching the arm, but didn't really want to start grinding so soon. Even if there was a way to make a 32t fit, the arm would catch the chain since the clearance is so tight. I'll upsize to a 34t and see what happens. Questions emailed to Middleburn and MTB Tandems have gone unanswered. I thought about the spacer idea, but there really isn't enough room for a spacer at all.
    If I am reading all of this correctly, you have 2 interference problems. First, the inside diameter of the chainring is hitting the crankarm. This should be easy enough to fix by filing the ring in the correct locations. I have done this on various rings to get them to fit an old Race Face crankset. The second problem is, even if you get the chainring filied down and it mounts correctly, the chain will hit the back of the crankarm. This problem is much harder to solve. I would personally not modify the crankarm at all, I think that is just asking for trouble. I think your only options are to try a larger chainring, or try a different crankset. I would get a 34t ring and try it, and then use the 32 on the inside. Just increase your cog sizes slightly. Remember, larger rings and cogs last longer and run smoother!

    Good luck,
    Mark

  25. #25
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    Solution

    An Action Tec 34t chainring fits. Barely, but it does fit. I doubt any other brand of 34t ring wouldn't come close without grinding something down.

  26. #26
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    Im having a similar problem - i have a 5 arm XC and 4 arm DUAL spider. Of my collection of 36T rings, only the middleburn standard alloy ring (3.5mm wide) will fit clear of the back of the crank arm. All the others (4arm e-thirteen (3.2mm), 4arm thorn (5.0mm), 5 arm middleburn hardcoat (5.1mm thick)) touch the back of the crank arm before fitting flush on the outside of the tabs.

    I have sent an email to middleburn to ask whether the XC 4arm spider gives more clearance (as it is set for a 2mm narrower chainline than the DUAL spider) but not had a reply yet.

    On caomparing all the ring cut out profiles I think to make it fit I will have to grind a cutaway into the chainring. Chain clearance doesnt look an issue, but then Im using a 36T ring, so for smaller rings Im not so sure.

  27. #27
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    You may have better luck with the XC spider. I never tried it though. I never did hear back from Middleburn when I emailed and asked them to simply indicate the smallest compatible ring. Good luck with your project. My 34t Actiontech cleared . . . mostly. I ended up having problems with the chain rubbing on the crank. I'm giving up on the Middleburn for dingle use and using it on my geared bike.

  28. #28
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    cheers for that.

    At least Ive got one set up that will work for now, and will have a go at modding for the others.

  29. #29
    HHL
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    Somebody mentioned a solution above, I believe. Haven't seen this thread for a while, but the cleanest solution, rather than cutting up all your stuff, would be to go with a bottom bracket that would give you a few more mm, at least on the driveline side. Slightly higher Q-factor, but you would adapt. Phil Wood has offsets, or SKF has 118 mm, etc.

  30. #30
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    I'm not sure how the width of a bottom bracket has any impact on the clearance of a chainring to a crank arm. The chainring is attached to the crank, not the BB.

  31. #31
    HHL
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    You are right. I don't know what I was thinking, other than maybe about another thread where chainstays were an issue.

  32. #32
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    had a reply from Middleburn:
    The XC spiders now run 50mm as well to work with Shimano front mechs.
    The solid 36t ring does fit on the outside of a dual spider.
    We have 36t UNO rings in 1/8 thickness.


    SO will prob sell on my 4arm 36T collection to fund one of the above.

  33. #33
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    id be hesitant to grind down an SS chainring. you'll end up folding it. What about using spacers between the spider ant the ring to back it away from the crank arms?

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