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Pedal threads

Posted: 17 Oct 2020, 8:06am
by robert17
People, the next chapter of my restoration learning journey is that the lovely Stronglight chainset a kindly forum member sold me, requires 14 x 1.25 threded pedals, not the now standard 9/16. Doing some research, it appears that such pedals are rare and that tapping the crank threads out to 9/16 would be the way forward.

Well that's fine except tapping is something I've yet to try, Indeed I don't have the tools. Is this an easy task or would I be better off paying someone to do it for me?

Thank you.

Robert.

Re: Pedal threads

Posted: 17 Oct 2020, 8:31am
by iandusud
You could buy a pair of taps from around £20 and you shouldn't have any difficulty using them. However as you are not likely to have much use for them again it might make more sense to get a local bike shop to run their taps through the cranks.

Re: Pedal threads

Posted: 17 Oct 2020, 8:34am
by Jdsk
I've just done my first tapping on the notorious tandem trailer trike.

iandusud wrote:You could buy a pair of taps from around £20 and you shouldn't have any difficulty using them. However as you are not likely to have much use for them again it might make more sense to get a local bike shop to run their taps through the cranks.

Exactly, unless you think you'll be using them again.

Jonathan

Re: Pedal threads

Posted: 17 Oct 2020, 8:41am
by robert17
Do you have any ideas how much that would cost? Does not appear to be a big job.

Re: Pedal threads

Posted: 17 Oct 2020, 8:47am
by David9694
You’ve presumably read Sheldon Brown?

Older French bicycles used a 14 mm x 1.25 mm thread, but these are quite rare. French-threaded pedals are commonly labeled "D" and G" (French for "droite" and "gauche" (right and left). A French pedal will start to thread into a 9/16 x 20 crank (and vice versa), but will soon bind. Do not force it, or it will damage the crank. Aluminum French cranks are easily rethreaded to 9/16" x 20 TPI.

From my experience of trying to re-tap a damaged crank thread for a helicoil, you’ve got to get or keep the 90 degree angle spot on, or you will get that queasy feeling that something is “off”.

Re: Pedal threads

Posted: 17 Oct 2020, 8:55am
by robert17
They are marked 14 1.25 on the back.

Re: Pedal threads

Posted: 17 Oct 2020, 9:54am
by Brucey
it is possible that the cranks have already been retapped to BSC; have you tried a pedal in them?

BTW retapping is, in this case, a five minute job.

cheers

Re: Pedal threads

Posted: 17 Oct 2020, 9:56am
by Cyril Haearn
I should be afraid of damaging the thread so the cranks could no longer be used

Re: Pedal threads

Posted: 17 Oct 2020, 12:42pm
by robert17
I tried a new pedal, but they bound quite quickly, so stopped.

Re: Pedal threads

Posted: 17 Oct 2020, 5:07pm
by Brucey
you need the thread retapped, French pedals or different cranks then.

cheers

Re: Pedal threads

Posted: 17 Oct 2020, 5:27pm
by robert17
I've found someone to retap the threads. A bike shop I won't name wanted to drill a larger hope and glue in an insert with a 9/16 thread! Thanks but no thanks I said. The guy told me that this what he does for cranks with damaged/stripped threads.

Re: Pedal threads

Posted: 22 Oct 2020, 9:08am
by alexnharvey
robert17 wrote:I've found someone to retap the threads. A bike shop I won't name wanted to drill a larger hope and glue in an insert with a 9/16 thread! Thanks but no thanks I said. The guy told me that this what he does for cranks with damaged/stripped threads.


It's not a shameful suggestion and such inserts are a common repair for damaged threads in cranks and all sorts of other parts and devices. Threadlocking agents are essentially specialist glues.

Re: Pedal threads

Posted: 22 Oct 2020, 9:21am
by Mick F
Brucey wrote:you need the thread retapped, French pedals or different cranks then.
Yes, I agree.

Cheapest option is to buy French pedals perhaps.
They must have all the same pedals as the rest of us, just different spindles.

Re: Pedal threads

Posted: 22 Oct 2020, 11:46am
by Brucey
alexnharvey wrote:
robert17 wrote:I've found someone to retap the threads. A bike shop I won't name wanted to drill a larger hope and glue in an insert with a 9/16 thread! Thanks but no thanks I said. The guy told me that this what he does for cranks with damaged/stripped threads.


It's not a shameful suggestion....


I agree, but it is a pointless one.

FWIW I think I have a set of French-threaded (vintage) pedals here.

cheers

Re: Pedal threads

Posted: 22 Oct 2020, 12:43pm
by fastpedaller
Mick F wrote:
Brucey wrote:you need the thread retapped, French pedals or different cranks then.
Yes, I agree.

Cheapest option is to buy French pedals perhaps.
They must have all the same pedals as the rest of us, just different spindles.


No they have Frogs Feet - so quite different :lol:
Not intended to be offensive, I'll add