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Old 08-11-06, 10:10 AM   #1
Road Fan
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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?

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Old 08-11-06, 01:56 PM   #2
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The old crank arm has french threads.
Do not attempt to fit a 'modern' pedal into this crank.
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Old 08-11-06, 01:57 PM   #3
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Clean threads with stiff brush, grease and install.
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Old 08-11-06, 04:15 PM   #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.
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Old 08-11-06, 04:26 PM   #5
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if they are french wouldn't they get stuck half way through and have them sticking out all goofy like?
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Old 08-11-06, 04:38 PM   #6
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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.)

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Old 08-11-06, 04:42 PM   #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.
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