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Fixing threads on Campy Pedal

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Fixing threads on Campy Pedal

Old 05-25-23, 08:59 PM
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Fixing threads on Campy Pedal

Hey all, I've got a 70's Campy pedal that looks to have damage to the threads (won't go on a crank). I've seen lots of ways to re-thread/repair the cranks, but can the pedal threads be repaired? My local shop says they don't do it.
Thanks,
Rich
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Old 05-25-23, 09:32 PM
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Pics would help, but depending on the damage you could use a triangle file, a thread chaser or a lathe.
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Old 05-25-23, 09:44 PM
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Originally Posted by FrejusFlyer
Hey all, I've got a 70's Campy pedal that looks to have damage to the threads (won't go on a crank). I've seen lots of ways to re-thread/repair the cranks, but can the pedal threads be repaired? My local shop says they don't do it.
"won't go on a crank" is shaky ground for assuming the threads are damaged. I'm having trouble imagining what kind of damage could keep it from threading in, but is not visible to the eye. Or maybe you can see damage? That wasn't clear to me from your description. Well-focused close-up pics sometimes show things you can't see by eye. Please supply photos if you are able.

Have you tried it on more than one crank? Any chance your crank is French-threaded?

Besides the nominal thread size, there is also a "class of fit", basically how much smaller the actual dimension is than the nominal dimension. Cheaper pedals generally are made with a smaller thread, to fit easily into cranks whose threads may not be made to tight tolerances. Campy pedals are made with a tighter fit and can be difficult to thread in, even when the crank thread is high quality, such as with Campy cranks.

Repairing the thread is going to be difficult due to the thick hard chrome plating. A machinist can do it, but it requires taking the spindle out of the pedal, and will probably cost more than a pedal is worth. But don't even think about repairing it until you determine what the problem is.

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Last edited by bulgie; 05-25-23 at 09:54 PM.
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Old 05-25-23, 09:52 PM
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Originally Posted by Reynolds
Pics would help, but depending on the damage you could use a triangle file, a thread chaser or a lathe.
Most thread chasers will quickly become dull trying to cut through the chrome on a Campy spindle.

The triangle file will also be dulled by the chrome, but they aren't too expensive, so it might be worth sacrificing one. That takes a fair amount of filing skill to do well though. Good eyesight too, and/or watchmaker's magnifiers.

If the pedal is useless otherwise, then you have nothing to lose by trying I guess. Don't let my negativity stop you, if you have the gumption to try it yourself. It's not like Campy pedals are so rare that it's a sin to ruin one by trying to fix it.

You can also swap in a good spindle from a pedal that was damaged somewhere else, like cage worn out from cleats, or crash damage, as long as it didn't bend the spindle. And those spindles pretty much never bend, they're ridiculously strong! The crank will bend before the spindle will, in my experience.
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Old 05-25-23, 10:16 PM
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Originally Posted by FrejusFlyer
Hey all, I've got a 70's Campy pedal that looks to have damage to the threads (won't go on a crank). I've seen lots of ways to re-thread/repair the cranks, but can the pedal threads be repaired? My local shop says they don't do it.
Thanks,
Rich
Cranks are soft, pedal axles may be the hardest part of a bike, save for maybe the BB spindle.

Any attempt at manipulating them needs to be precise and very capable, the fixing part needs to be harder and not allowed to do more damage, often very challenging and a crap shoot on a good day.
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Old 05-25-23, 10:24 PM
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Is it possible they are French threaded?

Remember that if the crankarms are French threaded, putting an English threaded pedal on won’t work. Don’t know if this is the issue. Also, you can buy fairly inexpensive 9/16 pedal tap kits on Amazon or EBay to repair threading if it is just damaged. Worse case scenario is a larger diameter tap and the use of a helicoil to restore standard diameter threading.
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Old 05-25-23, 11:20 PM
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Thanks for the help, all! Nope, it's not French threaded. I've tried the pedal on multiple cranks and while I can't see any damage to the threads, when I get about three turns in it stops hard on three different cranks. Don't want to force anything. The right-hand pedal from the set goes on without any issue.
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Old 05-25-23, 11:54 PM
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New set of cranks? Do other pedals thread on without issue?
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Old 05-26-23, 12:17 AM
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Reads time to look for an orphan pedal for the shaft. they do show up, and often with the dust cap, I have purchased one when a pedal on a bike I bought had a bent shaft.
I could feel it when riding the bike.

a triangular file will have a 60 degree inclusive angle, I forget what the 9/16 x 20 thread profile angle is… 55 degrees?
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Old 05-26-23, 12:58 AM
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Well, since I have Hozan pedal taps that have a long gradual taper, I would just chase the threads on my chosen crank until the pedal goes in. Snug is good; even needing a longish pedal wrench to tighten it would be acceptable to me (not a cheater bar mind you, just a regular pedal wrench).

On my pedal taps, usually going about halfway up the taper is good enough, but if I had to run the tap all the way through, tapping it to the maximum size these taps can make, is still within tolerance. Some other pedal taps are that way too, I believe Eldi have that feature?

If these pedals are from the '70s, unless they are truly NOS (possible but very rare), then this tight one has been in a crank before. Can you say anything about their provenance? My guess is the tight one is just "on the tight side", always has been. Have you tried just reefing on it? With anti-sieze compound maybe or just grease. Show it who's boss!

I would consider that far better than trying to file the threads (precise, evenly all the way down) with a triangle file, that's just not gonna happen no matter how good you are at filing. Especially since the file will quickly dull from the chrome.
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Old 05-26-23, 06:10 AM
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I had a Superleggeri pedal that was as you described. The damage was on the lead in or first turn of the thread . I used a Tri-file to get the damaged area smooth then carefully chamfered the end of the pedal on a grinder. It started in the crank ok but was still a bit snug. Thankfully I have a really long Eldi pedal wrench that got it all the way in . I did use just a dab of grease to aid in the turning of the pedal and to keep it from tearing the threads in the crank.
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Old 05-26-23, 06:54 AM
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Originally Posted by bulgie
You can also swap in a good spindle from a pedal that was damaged somewhere else, like cage worn out from cleats, or crash damage, as long as it didn't bend the spindle. And those spindles pretty much never bend, they're ridiculously strong!
That's probably the easiest path. Campagnolo Record/Superleggero and Gran Sport spindles are interchangeable; the salient differance is that Record spindles have rifling to help expel contaminants. Triomphe and Victory pedals have Gran Sport spindles. Zeus, Gipiemme, and some Ofmega spindles can also work in Campagnolo pedal bodies.
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Old 05-26-23, 11:01 AM
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Harsh light and a jewelers loupe for close inspection, if no real damage discernable, "burnishing" with wire wheel, anti seize, good, long pedal wrench and 1 step forward, 2 steps back workover can often smooth things out.
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Old 05-26-23, 11:38 AM
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Thanks again for the help, everyone! I'll try burnishing and if that doesn't work, look for another spindle. Here are some photos for the curious.



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Old 05-26-23, 12:03 PM
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Originally Posted by FrejusFlyer
Thanks again for the help, everyone! I'll try burnishing and if that doesn't work, look for another spindle. Here are some photos for the curious.


This is what we needed, those first thread and a half look to be dull and mishapen. I would also get a thread file try to dress those very carefully a bit.

You could also carefully "spin grind" them down just a bit so the first full threads that grab are the next sharper ones that appear to be much more right from here.
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Old 05-26-23, 02:15 PM
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Thanks again!
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Old 05-26-23, 02:24 PM
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remember that Campy pedal threads of that vintage are cut with a 55 degree crown angle while the crank arm threads likely have a 60 degree angle which is the ISO standard.

there is another detail related to whether the threads are flat topped or radiused

so either of those details could explain the resistance you are encountering.

ISO thread diagram below.

/markp

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Old 05-26-23, 02:33 PM
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+1 on the recommendation to use anti-seize compound when you assemble

and running a tap through the left hand crank arm prior to fitment.
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Old 05-26-23, 02:45 PM
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@mpetry912, do you think the 55º angle might be a contributor to the problem?
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Old 05-26-23, 02:52 PM
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I don't think it's a compatibility problem as the right-side pedal went on the crank like butter.
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Old 05-26-23, 03:01 PM
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Originally Posted by FrejusFlyer
I don't think it's a compatibility problem as the right-side pedal went on the crank like butter.
Agreed, aside from the threads.

The first pic above clearly shows mishapen first couple of threads to me, sort of folded over instead of a centered peak like they should be.

The pedal axle is far harder than the crank so brute force properly applied would likely force it into submission but it might also split the eye in time.
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Old 05-26-23, 03:09 PM
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Originally Posted by noglider
@mpetry912, do you think the 55º angle might be a contributor to the problem?
Yes, Tom, it's a possibility. I have found that campagnolo pedals thread in "tite" on non campagnolo crank arms.

the threads in the picture look fine. To me the "tell" is that he says it goes in about 3 turns, which means the pedals start and then the mismatch in angle or thread crown builds up and causes them to become harder to turn.

OP is smart not to force it.

Portlandjim is the person who would really be qualified to opine. he knows his way around threads and stuff.

/markp

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Old 05-26-23, 03:25 PM
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Originally Posted by FrejusFlyer
I don't think it's a compatibility problem as the right-side pedal went on the crank like butter.
OK, did not know that. that's a tell.

thanks

/markp
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Old 05-26-23, 03:50 PM
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Originally Posted by FrejusFlyer
Thanks again for the help, everyone! I'll try burnishing and if that doesn't work, look for another spindle. Here are some photos for the curious.
Great photos! Thanks for that.
Those threads look completely fine to me. The first thread or 1-1/2 threads being a little truncated is normal, not damage IMO.

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Old 05-26-23, 05:21 PM
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