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Old 07-30-10, 05:24 PM   #1
tugrul
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Can non cross threaded pedals sieze to the point they rip the aluminum threads out?

I just put a fair amount of effort (no additional leverage, just a 10" wrench) to remove pedals off a bike teetering on being too rusty to bother with, and on both sides the pedal threads took a fair amount of aluminum with them (cranks are Sugino VPs).

Now I'm wondering whether I'm at fault for being too gung-ho about getting these pedals off before soaking them in ammonia or something (they never gave after the initial movement), or whether they were cross threaded to begin with. I've put waaaay more force into removing pedals before (me with a 6 foot pipe), and all that resulted in was a warm pedal.

Have you seen a properly threaded pedals so seized it took some aluminum with it?



As a side question, how much should I expect to get charged to have the cranks re-tapped? (I can thread pedals on, but not sure whether I feel good about it) Or should I just buy a set of Park TAP-6 taps for about $35 so I can be prepared and then this will never happen again
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Old 07-30-10, 07:31 PM   #2
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Pedals, bottom and top.


DS Crank

NDS Crank

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Old 07-30-10, 07:55 PM   #3
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That does not look good. Remember that the pedal shafts bear your entire drive force, and there is a natural torque moment which tries to rip them out of the cranks. If you promise never to stand/"dance" on the pedals, you can cautiously use those cranks awhile longer.
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Old 07-30-10, 08:05 PM   #4
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You could get a heli-coil put in for 1/2" pedals, but that limits your pedal selection, and might be more time and hassle than it's worth unless you have machinist friends.
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Old 07-30-10, 08:11 PM   #5
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Quote:
Originally Posted by tugrul View Post
I just put a fair amount of effort (no additional leverage, just a 10" wrench) to remove pedals off a bike teetering on being too rusty to bother with, and on both sides the pedal threads took a fair amount of aluminum with them (cranks are Sugino VPs).
I bet the rust expanded the pedal axles to the point they were never going to come out without taking the cranks with them. I don't think there's enough material left in the crank to hold pedals adequately.

My recommendation: toss it all out. There's nothing worth saving.
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Old 07-30-10, 08:14 PM   #6
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Heli-coils, for sure. Done properly, they'll be better than new.
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Old 07-30-10, 09:11 PM   #7
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Don't blame yourself, those were hopeless before you got to them.

Heli-coils and a wire-brush mounted on a grinder for the pedals if it's worth it to you - or just toss the lot.

And - I know you know this but some newbies may not - this is one reason why you always GREASE the threads.
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Old 07-30-10, 09:15 PM   #8
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It's called galvanic corrosion. When you put two dissimilar metals in contact they begin to corrode. They will eventually become basically welded together if you haven't taken precautions to prevent the corrosion. And when you try to remove the part, it just rips the threads right out. Pedal threads and spoke nipples always tend to be problem areas and should always get a dab of anti-seize compound.
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Old 07-30-10, 09:32 PM   #9
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Bummer. Didn't know it could get that bad.

It was a $5 Centurion Accordo, mid-80s sea green/gray two tone model. If there are any more surprises like this, it may just never see the road as a complete bike again.
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Old 07-30-10, 09:37 PM   #10
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Ripped the pedals right out. That galvanic corrosion that Hydrated refers to is the same thing that keeps stuck seatposts bonded to many frames. These pedal threads give a pretty good idea as to the strength of such bonds.

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Old 07-31-10, 05:04 PM   #11
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Yup. I haven't had that specific (pedal to crank) problem, but on my folding bike, which is mostly aluminum, I've had several stainless steel fittings get so comfortably mated to aluminum that the same thing happened. Stainless... but not corrosion-proof. As said above, always grease the threads. And when you buy a new bike, take every every everything apart, and grease it all, and put it back together. Yes, that's a PITA, but the alternative (galvanic corrosion) is at least an equal PITA, fnot worse.
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Old 07-31-10, 05:44 PM   #12
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It's not the first time I've seen pedals do that to a crank - all because someone ran them in dry.

If you want to save the pedals, the best way is to get right and left handed 9/16 dies and run them back over the threads.
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