Multiple pedal thread standards?

[professerr]

I was setting up a beater rain bike today and tried to install a pair of modern-ish Time RXS pedals on an old Record crank set from the 1980s. Previously, and for the last 20+ years, I had installed various iterations of the original Time Equip Pro’s from the same 80’s era (I love the wide range of motion of the old Times).

When I tried to thread the newer RXS pedals in, they would bind about ½ a turn after the threads started to catch. Same on both cranks, I was careful not to cross thread, and there was plenty of grease. I used just a bit of force for a small fraction of a turn, thinking perhaps there was dirt, but afterwards I could see a tiny bit of silver on the pedal thread when I inspected. The original Equip Pros thread ¾ of the way in with just hand pressure. Figured I should post here before stuffing things up any more than I have already.

I thought all pedal threads were a standard pitch. Not so?

[Noteddy]

Pretty hard to imagine, but you [I]could[I] have a French threaded crank. From his holiness Sheldon brown:

"Most French bikes sold in the U.S. used standard thread pedals:
9/16" x 20 TPI (14.29 mm x 1.27)
But older bikes made for the French market used a slightly smaller thread:
14 mm x 1.25 (.551" x 20.32 TPI)
If your cranks are made for standard-thread pedals, a French-thread pedals will fit in, but be very loose and will be unusable. It is not possible to put a standard pedal into a French crank without considerable violence.
It is possible to re-tap French cranks to take standard pedals. Use standard 9/16" x 20 taps."

By the 80's many Campy cranks had the threading (9/16 x 20) marked on the back of the crank arm. If in doubt take it to your LBS and the should have a set of taps they can run through to bring them up to spec.

In any case, it sounds like you should have the threads chased, or risk trashing the cranks and the pedals.

[zetroc]

Any chance the drive side crank came off of a tandem?

[Noteddy]

Any chance the drive side crank came off of a tandem?

Brilliant thought.

On rereading with both eyes open, it sounds like you have had pedals in these cranks before? If that's the case, and the new pedals seem clean and have been in cranks before, I'm baffled. I'd probably still run a tap through them.

[professerr]

Pretty hard to imagine, but you [I]could[I] have a French threaded crank. From his holiness Sheldon brown:

"Most French bikes sold in the U.S. used standard thread pedals:
9/16" x 20 TPI (14.29 mm x 1.27)
But older bikes made for the French market used a slightly smaller thread:
14 mm x 1.25 (.551" x 20.32 TPI)
If your cranks are made for standard-thread pedals, a French-thread pedals will fit in, but be very loose and will be unusable. It is not possible to put a standard pedal into a French crank without considerable violence.
It is possible to re-tap French cranks to take standard pedals. Use standard 9/16" x 20 taps."

By the 80's many Campy cranks had the threading (9/16 x 20) marked on the back of the crank arm. If in doubt take it to your LBS and the should have a set of taps they can run through to bring them up to spec.

In any case, it sounds like you should have the threads chased, or risk trashing the cranks and the pedals.

Thanks. I just checked and, yep, the cranks are marked 9/16 X 20 F.

[professerr]

Brilliant thought.

On rereading with both eyes open, it sounds like you have had pedals in these cranks before? If that's the case, and the new pedals seem clean and have been in cranks before, I'm baffled. I'd probably still run a tap through them.

It is possible the drive side crank came off a tandem -- I bought it off someone in college in the the 1980s -- but very, very unlikely since he was a racer.

Yep, I used to run old Time Equip Pros in the cranks, and the Time RXS's I want to install previously lived happily in some Campagnolo 10-Speed Record cranks.

Threads are clean, but not spotless. Maybe there's something there.

[Bssc]

unless you want to cut new threads never use a tap to chase threads use a chasing tap

measure the threads it is you best bet for figuring out the issue

[Jukebox]

unless you want to cut new threads never use a tap to chase threads use a chasing tap

measure the threads it is you best bet for figuring out the issue

How do the old pedals from this crank fit into a modern crank, like your 10speed record?

[j44ke]

My brain is foggy due to a cold, but as I remember the older Campagnolo cranks were threaded the same thread pitch as modern pedals (given the same thread standard designation) but "threadform" is different slightly. Most threads are V shaped, but there can be variances in the shape of that V. I think the old Campagnolo pedal threads have a more acute (sharper?) V than newer pedal threads which I think are blunter at the point of the V. So when you thread in newer pedals (I don't remember when this changed) you are reshaping the threads a bit, which is probably better done with a chasing tap.

[professerr]

How do the old pedals from this crank fit into a modern crank, like your 10speed record?

Good question. I just tried the old Time pedals (from late 80s or early 90s) and they will thread into the new 10 speed record cranks, but they are a very loose fit and wobble. The spindles of the old Time pedals bear the marking "9/16 X 20" (well, actually, they are worn and all thats left just says "/16 X 2"). So it appears both the old Record cranks and the old Time pedals use the modern, normal 9/16 X 20 thread standard. Yet the old Time pedals don't fit the modern, normal 10 speed Record cranks, nor do the old Record cranks fit the modern, normal Time pedals. I'm baffled. All threads clear of gunk too.

[professerr]

My brain is foggy due to a cold, but as I remember the older Campagnolo cranks were threaded the same thread pitch as modern pedals (given the same thread standard designation) but "threadform" is different slightly. Most threads are V shaped, but there can be variances in the shape of that V. I think the old Campagnolo pedal threads have a more acute (sharper?) V than newer pedal threads which I think are blunter at the point of the V. So when you thread in newer pedals (I don't remember when this changed) you are reshaping the threads a bit, which is probably better done with a chasing tap.

Hmm...perhaps this is the issue.

[professerr]

Took the bike to the LBS. They chased the threads and all is good. They weren't really sure what the issue was, said something about oxidation, and confirmed the crank threads were standard threads that, post-chased, worked fine with modern pedals. The end.

[devlin]

Bike shops are awesome!

[professerr]

Postscript: One thing still bothers me. The old Time pedals from the '80, which now have been confirmed to have standard threads and were threaded for many years in standard threaded cranks, now don't fit my modern standard thread cranks. They are too loose and wobble. Weird.

[j44ke]

Again, I think it is the threadform difference. Now that your old cranks have been chased, you will likely find that the old pedals will be a bit looser on those as well.

There definitely was a change. At one point, I had three old cranksets - NR and SR - and when I switched them from ancient Look pedals to the new Keo pedals, I had to do a little work. It wasn't wear and tear on the threads - there was a difference. But it wasnt thread pitch, so I read around and found reference to threadform changes in another field (cars I think) that had to do with automation. So things could be assembled quickly with machines or power tools or whatever, the shape of the thread (threadform) was changed (but pitch was not.) I don't know for sure, but I suspect the same change occurred in bicycle stuff as well. And perhaps only pedal threading as it may have used a tighter fitting threadform than other areas because of the inherent stress. Who knows? Once it is fixed, as you said, done.

[Hindmost]

Regarding old cranksets, NR and SR, I heard one story that the factory taps were so worn that a tight fit would result.

And another: Stuck Pedal Removal by Jobst Brandt ...that the tight fit was intentional. Maybe this leads back to a change in threadform?

[Bssc]

hopefully it was a real chase and not a cut if they cut it will cause this issue because of material removed making a deep V grove instead of a more U as done by factories

[Human Epic Jolt]

you have been virtually bathed in pedal threads. one more heart.

[bikinchris]

Regarding old cranksets, NR and SR, I heard one story that the factory taps were so worn that a tight fit would result.

And another: Stuck Pedal Removal by Jobst Brandt ...that the tight fit was intentional. Maybe this leads back to a change in threadform?

I can verify that most Campy cranks have very "tight" threading and sometimes had to be tapped to clean out the threads before a pedal can be installed without problems. it has happened probably dozens of times in the hundreds of Campy equipped bikes I have built.