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  1. #1
    Senior Member Road Fan's Avatar
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    Crank Arm Pedal Thread Repair

    I have an old aluminum crank arm with 9/16 pedal thread, and the pedal is hard to thread in halfway, and will not go all the way without more force than is sensible. The arm threads look rough, and the pedal will thread into a good arm.

    So I need to repair the threads.

    1. Do I need a tap, or a "thread chaser?"
    2. What is a thread chaser, anyway?
    3. Are thread chasers just good for pushing out dirt, or do they affect the threads themselves?

    Do I have to assemble the pedal to the arm with reduced torque after the repair?

    Ken "needa get the bike going!"

  2. #2
    Listen to me powers2b's Avatar
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    The old crank arm has french threads.
    Do not attempt to fit a 'modern' pedal into this crank.
    Quote Originally Posted by SBFixed View Post
    You're a dick, if your bike gets stolen I hope that you don't get a thread.

  3. #3
    Listen to me powers2b's Avatar
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    OR
    Clean threads with stiff brush, grease and install.
    Quote Originally Posted by SBFixed View Post
    You're a dick, if your bike gets stolen I hope that you don't get a thread.

  4. #4
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    Or, if you have junk pedals lying around, make your own taps. Cut 3 slots legnthwise across the threads with a dremel tool, then put them in using kerosene, wd 40 as cutting oil. (Remember, you need 2, LH and RH threads)

    If it is french threaded, you can still use non french pedals, the pedals just go in very snug.
    Il faut de l'audace, encore de l'audace, toujours de l'audace

    1980 3Rensho-- 1975 Raleigh Sprite 3spd
    1990s Raleigh M20 MTB--2007 Windsor Hour (track)
    1988 Ducati 750 F1

  5. #5
    Life is short Ride hard
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    if they are french wouldn't they get stuck half way through and have them sticking out all goofy like?

  6. #6
    Gone, but not forgotten Sheldon Brown's Avatar
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    Quote Originally Posted by Road Fan
    I have an old aluminum crank arm with 9/16 pedal thread, and the pedal is hard to thread in halfway, and will not go all the way without more force than is sensible. The arm threads look rough, and the pedal will thread into a good arm.

    So I need to repair the threads.

    1. Do I need a tap, or a "thread chaser?"
    2. What is a thread chaser, anyway?
    3. Are thread chasers just good for pushing out dirt, or do they affect the threads themselves?

    Do I have to assemble the pedal to the arm with reduced torque after the repair?
    A thread chaser is generally just a cheapo tap. Bicycle pedal taps are a standard repair tool, any decent bike shop will have a pair. You can buy a pair for about $35. Thread the tap in from the back side of the arm, so that damaged threads won't get it running cockeyed.

    Once you have repaired the threads, tighten the pedals normally (pretty snug.)

    Sheldon "Day Is Done...Gone The Sun..." Brown
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  7. #7
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    Quote Originally Posted by ryanparrish
    if they are french wouldn't they get stuck half way through and have them sticking out all goofy like?
    I have Stronglight cranks (French) and they work fine with non-french thread pedals, like I said, just a tight fit.
    Il faut de l'audace, encore de l'audace, toujours de l'audace

    1980 3Rensho-- 1975 Raleigh Sprite 3spd
    1990s Raleigh M20 MTB--2007 Windsor Hour (track)
    1988 Ducati 750 F1

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