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Thread: Filing Cotters

  1. #1
    peaced out deez's Avatar
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    Filing Cotters

    I put the cranks back on my '72 Raleigh last night and when I installed the new cotters the pedals didn't sit exactly 180 degree apart. I understand that I need to file the flat on the cotters to change the angle to fix this. Should I be filing both cotters or just one of them?

    In Sheldon's Cottered Crank Article he says
    the depth and angle of the flat varies considerably. For this reason, it is best to replace cotters in pairs. If mis-matched cotters are installed, the cranks will not be 180 degrees apart.
    My concern is that I'm using 2 brand new cotters, I bought a 10 pack from ebikestop.com. How could they be mismatched?

    This is my first time installing cotters...any advice would be really helpful, thanks.

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    The Improbable Bulk Little Darwin's Avatar
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    Did you install the cotters in opposite directions? If you install them in the same direction you can have an offset issue too.

    i.e. if the cranks are vertical, and the head of one cotter is facing the front, the head of the other should be facing the rear.

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    peaced out deez's Avatar
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    to clarify, Both the cotters fit just fine and hold the cranks solidly. Its just that the cranks don't end up 180 degrees apart. Everything I've read says to be careful filing the cotters so as not to change the angle of the flat, but it would seem that I do need to change the angle of the flat on either one or both of the cotters.

    am I wrong?

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    peaced out deez's Avatar
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    Quote Originally Posted by Little Darwin View Post
    Did you install the cotters in opposite directions? If you install them in the same direction you can have an offset issue too.

    i.e. if the cranks are vertical, and the head of one cotter is facing the front, the head of the other should be facing the rear.
    To be honest I'm not sure, I'll check tonight. The arms were probably like 5 degrees off 180.

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    Randomhead
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    that sounds like you have wear on the crank axle. I can't imagine they would only be 5 degrees off if they were in wrong.

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    peaced out deez's Avatar
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    How far off would you expect them to be if they were in wrong?


    I had my LBS disassemble the BB for me and they had commented that the Spindle and Cups were in exceptional condition and looked hardly ridden...not to be contrarian but I'm fairly confident the spindle is ok.

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    The Improbable Bulk Little Darwin's Avatar
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    Quote Originally Posted by deez View Post
    To be honest I'm not sure, I'll check tonight. The arms were probably like 5 degrees off 180.
    As Unterhausen mentions 5 degrees sounds like it is too small to be an issue with improper installation.

    I agree that since they are new, they should be matched... However, since you have 10 cotters to choose from, you may want to look at them very closely to see if swapping a pair of them will make a difference.

    Are you using a clamp or a cotter press of some type?

    I would look for burrs, protrusions, dirt etc that could keep the cotters from seating properly. This could be on the crank, the spindle or the cotter.

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    The Improbable Bulk Little Darwin's Avatar
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    Quote Originally Posted by deez View Post
    How far off would you expect them to be if they were in wrong?
    It would be off by about twice the angle of the bevel of the cotter, so about 20 degrees or so (as a guess).

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    peaced out deez's Avatar
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    welll....I suppose it could have been as much as 20 degrees...i'm bad at estimating that stuff.

    I'm not using a clamp or cotter press, they seem to go in pretty easy I just didn't want to hammer them in with the angle being so far off.


    Is it correct that on a properly matched set of cotters the flats should match up and cancel each other out?

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    Quote Originally Posted by deez View Post
    Is it correct that on a properly matched set of cotters the flats should match up and cancel each other out?
    Yes.

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    peaced out deez's Avatar
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    I'll check it out when I get home and report back, thanks guys.

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    Before you start filing, an easy diagnostic/fix is to pull each cotter and then put each in from the opposite side of the crank arm from where you have them in now. That might just get them to mate up to the spindle as intended.

    Neal

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    My bikes became Vintage OLDYELLR's Avatar
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    Another possibility is that the left or right crank has been replaced at some point and they don't match.
    Last edited by OLDYELLR; 10-16-08 at 07:59 PM.
    1981 Nishiki Ultimate
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    "index shifters = frets on a fiddle"

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    peaced out deez's Avatar
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    Little Darwin, you were 100% correct with your response, I had installed both cotters facing in the same direction.

    When I flipped one around the cranks came into perfect alignment, no filing necessary.

    THANKS!

    **edit**

    and yes, i'm as bad as I thought I was at estimating the angle they were off by

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    ugh!! the dreaded crank cotter and being ocd myself about such details, if my cranks aren't 180 degrees set, it drives me up the friggin wall and all the cotters i've gone thru. at this point i am glad to be a good ol' single speed, fat tire lovin, chrome fenders shining cruiser man, allthough i did convert one to a s.a 3speeds (best of both worlds), but maybe my cottered experiences can help.

    with the crank arms off, look at the indentation that the cotter sits against and check both sides to see if the indentation is a 180 degees set, for starters. confirm that, then put your arms back on as if you were ready to slide the cotters in. this is strange but true, my austrian built jch had missaligned cranks and by simplely pulling the pins and reinstalling them THE OTHER WAY AROUND fixed the problem in some weird combonation. not sure if i reversed the direction of both cotters or just one, and which one? try this and try using different combo out to get it spot on.

    all fileing the cotters down will do is add more slop to the setup and if they get too skinny, they may be sucked thru the cotter hole on the crank arm. and i learned that just because one side went in "right", and the other arm looked to be throwing off the degrees, it may not necassarily be that second crank. to me, i have found out that those stupid cotters sometimes tend to be direction specific. just as long as you are using the right gauge cotter. ...

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    Senior Member Grand Bois's Avatar
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    If I hadn't filed these cotters, there wouldn't have been enough threads protruding to install the washer and nut. You also have to get the cotters to protrude the same amount on both sides. Getting it just right involves installing and removing the cotters a few times, and the only way to do it right is to use a good press.


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