Cycle Tourist

So I'm refurbishing a nice Peugeot uo-10. All the parts were there and working so what could go wrong? The pedals were these very ugly plastic mt. bike jobs so all I had to do is remove them and put on some nicer ones.
It didn't take long to realize the thread was wrong and the pedals were forced on. I took em off anyway. I'm not sure the cranks are savable but I've got other cranks. So since the standard crank puller worked easily, why are the pedals such a mess.
I have some 9/16th pedals coming but I tried these crap pedals on a standard crank and they don't screw on. It may be because the threads got messed up or???
Any advice would be appreciated.

63rickert

As a first guess the cranks were 14x1.25 French and someone forced in a 9/16x20. The two standards are close enough that can happen. Did either pedals or crank or both survive this? No idea. Very possible the pedals did exact same job a proper pedal tap would have. Pedals won't go into "standard" crank? You're sure thats not a standard French crank? I'd not even consider giving up on these parts until real sure.

dsbrantjr

It sounds like somebody may have forced 9/16-20 standard threaded pedals into the M14 x 1.25 French threaded cranks. Or cross-threaded them. Or put them into the wrong sides.

Cycle Tourist

Yeah, I think forced a 9/16 into the french threaded crank is what happened. The pedals won't fit a standard crank because they're a little messed up. I think the cranks survived,(just). The better course of action?? I'm thinking is complete the retap to 9/16 and move on with rebuild. Alternatively I could search for french pedals but I hate to go back and forth with the threads on these cranks. The pedals are headed to the trash.

Andrew R Stewart 

Agreed that chasing the threads to 9/16x20 is the best idea. If the tap is hard to start run it in from the inner side of the arm. Andy

sch

What can be seen of the threads in the cranks shows them to be clean and bright, not torn up or shredded as if cross threaded.
Since Fr 14Mx1.25 is about 0.05" smaller than 9/16x20 whoever put the latter in the former had to apply a lot of torque. A
light, lubricated chasing with a set of 9/16x20 taps should finish the thread nicely and make them usable with easy to find
pedals.

trailangel

I don't know, but that looks like one of the newer Stronglight cranks( I had one) and they are standard pedal threads. The fact that you used a standard crank puller could be a clue. They might say on the crank arms 9/16x20. You sure you are putting the right pedal on the right crank arm? Left pedal on left crank arm?

100bikes

It appears the you have a left pedal and right crank arm.
Curious how did someone get this combination to start threading in the first place?
Once they did get purchase, they would have applied a bunch of torque and the steel pedal spindle acted as a tap in the softer aluminum arm.

There are threaded inserts which can be found that would save the crank, but it would be easier to start with new stuff.
Rule of thumb regarding pedal threads - if the treads go uphill to the right is a right pedal, uphill to the left a left pedal.
Really, check it out!

sch

There is no possibility that a L threaded 9/16 (or M14 Fr L pedal) could be threaded into a R handed crank and leave the
the crank threads as clean as they look in the photo. So that did not happen. Anyone who has done threading with taps
larger than 1/2" knows that starting one requires a lot of torque and applied pressure, neither of which can be done with
a pedal/crank setup. 9/16x20 and 14Mx1.25 have essentially the same threads per inch for the thickness of the crank
and only differ by about 0.05" in diameter.

WizardOfBoz

I think sch has some good points.

For those not experienced with tapping, there's two basic types. Cutting taps have sharp edges that cut metal away from a drilled holed to leave threads. Form taps don't have any cutting edges. They're basically a tapered rod of hardened tool steel that has threads cut into it. To form tap you start with a hole that's a little bigger than you would for cut tapping. The form tap (with a lot of lubrication and force) is threaded into the hole and forms the threads by pushing metal around.

If someone ran a 9/16-20 pedal into a 14M1.25 hole, they essentially form tapped the larger (9/16 is 14.29mm) hole with thread with a 1.27mm (not 1.25) mm pitch. Not completely, because the original hole wasn't of proper size to form tap a 9/16 thread (its not big enough). There's more metal in the hole than a 9/16 form-tap could move around.

I'd try to thread in a pair of standard 9/16 pedals, using some oil to lube the process. If it's rough going (too hard to thread in) I'd have my LBS chase the threads. If you want to buy the proper taps and do it yourself, be VERY careful to ensure you start the tapping process with the tap parallel with the existing hole and threads. The UO-10 is a nice vintage bike. I like the Peugeot crank - good luck.

Cycle Tourist

I photographed a pedal at random so I may have a different pedal than I took of the photographed crank. They were NOT cross threaded, just forced into french threaded pedals. The bike's from 1980 so they're old cranks. It took a dying strain to remove the pedals but the treads stayed mostly intact. Some aluminum came out with the pedals but they don't look too bad.
I bought new taps on Amazon for about $20 and I'm pretty sure oil and patience will allow me to clean up the retaping done by the muscle job with the cheapo pedals. It is strange that the cable pullers screwed in perfectly and yet the pedals were french threaded. Working on french bikes always reveals some odd querk in construction but that's a new one. I'll try the taps and let you know how it goes.

WizardOfBoz

There are special tapping fluids made for aluminum (that work better than oil). Tap Magic is a standard brand, but Relton A-9 also gets good reviews. Not too expensive, either. A 4 oz bottle would be enough for dozens of cranks.

https://www.amazon.com/s?k=tap+magic...f=nb_sb_noss_2

A two-handled tap wrench is useful in ensuring that you tap the threads straight. For a 9/16 tap, I'd suggest the bar type, not the t-handled. The bar handle should be available for larger taps. For hand tapping, a 9/16" tap is reasonably big (which is why you want the proper fluid, above, and two handles).

Cycle Tourist

Love you guys and the detailed help I get. Thanks.
The 9/16 pedals got mashed on so, as you might expect the tapping went smoothly. The pedals showed up and screwed on easily so as soon as the sun makes another appearance, I'll take some pictures. This was the before pic.

Cycle Tourist

It was on CL at $150. I offhandedly said that $50 was as high as I'd be willing to go. He accepted, so naturally I had to go get it. The decals were pretty nice so I removed the rust and matched some silver paint. It fits me so maybe I found a bonafied clunker challange entry.🤓

WizardOfBoz

The frame is pretty nondescript, but the components are nice enough. I think it's a 1979, btw, $50 is a great deal and cleaned up this should be a great ride.

See here: https://www.bikeboompeugeot.com/Broc...0Brochures.htm

San Rensho 

As long as the threads in the cranks are good, just put the pedals in the cranks. I have stronglights that I put 9/16 in and they were fine, albeit a very tight fit and for years I have had absolutely no problem taking the pedals out and putting them back in. Needless to say with that tight fit I never had a pedal come loose. Make sure the threads on both the the pedals and the crank are meticulously clean and well lubricated with oil or grease before you install. I wouldnt tap anything.

JohnDThompson 

Those Peugeot Stronglight 104 cranks should have the pedal thread marked on the outer face of the crank arm, adjacent to the pedal eye, E.g. 170mm arm length, 9/16" x 20tpi thread:

Cycle Tourist

New pedals and tape.