When did 9/16" x20 become a standard pedal interface?
 

Just curious if anyone could let me know. Just wondering.

I have seen that thread on pre-WW2 English pedals and like many cycling standards was possibly started by Raleigh who dominated the cycle manufacturing world at the time, others might have more specific information.

It sounds like it was an "imperial" threading standard, do most likely quite old.....
The other standard, which is French (14 X 1.25, metric?) must be newer.

Here's some history,

https://www.boltscience.com/pages/screw6.htm

There has always seemed to me an unusual kind of "standard" in pedals, unusual in that it is never mentioned, much less specified.
It's the distance between the front and rear plates - the same in almost every quill and rat-trap.

It's also not the only standard as any Ashtabula crank proves.

Use of 9/16 by 20 goes back well before WWII. I've owned bikes from the 1920s and 30s that used it. They were all English-made bikes.

Good observation above - one-piece cranks ran 1/2 pedal shanks as standard. As a bit of additional trivial, the 1/2 inch shank even passed over to the relatively unusual American cottered cranks on bikes like the Schwinn New World and Superior prior to 1952.

That's a good question. I have never known any other threading for pedals and that's even on my old French bikes. I do know that back in the day pedals were changed and exchanged often. In the old bike shops there were many bikes with slightly bent Cottered cranks and trashed pedals waiting for repair...

It hasn't changed for decades and decades, one of the few standards that has stood the test of time.

But...Is the pedal-crank interface the next standard on the chopping block? I wouldn't put it the industry to 'innovate' us out of being able to use keep using old components on newer and newer parts. I'm trying to think of a way they'd change it up in order to fit larger bearings into the system and increase stiffness in general. Would the spindle ever become integral to the crank?

don't jink it :D

1915, 9/16" thread.


https://live.staticflickr.com/65535/...fc9b4834_k.jpgRola 33 by iabisdb, on Flickr

I was gonna say "probably about 1000 years ago." This antiquity is NOT BROKEN!

BMX did 1/2" for awhile. You can still buy them on Amazon

What's the distance between the plates? 2 1/4"?

Looking at my pics of the Wright Brothers bike in the Smithsonian, it looks like 1/2" to my uncalibrated eye-crometer.

https://cimg5.ibsrv.net/gimg/bikefor...1dc0a5cb38.jpg

I forget, but I think the bike is late 1890s or maybe early 1900s. US-made of course, so it shines no light on what England would have been doing then.

I have heard it said that the Wrights first used or popularized the use of the left-hand thread for the left pedal. Maybe apochryphal?

2 1/8 or 55mm. Pedals were made in Italy.

Still used on some kids bikes, BSO's, etc as well.

I have a 1911 Schwinn with 1/2 -20 pedals

Most Canadian bikes used that standard coming out of the 1800's. Adapters to 9/16 are out there if you want to use them.

It seems like the 9/16-20 pedal thread has been around about as long as the 1/4"-20 thread for camera tripods. You can mount a 100 year old camera on a modern tripod or a new camera on an old tripod. There were some bigger cameras that had a 3/8" mount, but they came with a bushing to adapt to the standard 1/4" screw.

Some delving into it with internet searching (which may or may not be apocryphal), it seems that it was standardized/published by the Cycle Engineers Institute (CEI) in Britain first in 1901 and in 1938 were revised as BSC (British Standards Institution as BS811:1950 and thereafter known as British Standard Cycle). By 1950 the standard of having 20 threads per inch with a 60º cut had been dropped but was still included in the index. 20 tpi is more common in Whitworth threads (BSW) but those are cut at 55º. I read that some early Campagnolo cranks were cut to 55º 9/16-20 threads and were considered an Italian thread.

1/2" x 20tpi has a long history on North American bikes. You can still find it on bikes with one-piece (aka "Ashtabula") cranks and some exercise bikes.

Like I said. ;)

I read this somewhere as well, so I asked the docent at the Wright Cycle Shop in Greenfield Village* at the Henry Ford Museum. His eyes bugged out and he said he'd never heard of that, but he'd find out.

Some of the items on display in the shop:

https://cimg3.ibsrv.net/gimg/bikefor...45ca2082e.jpeg



*Yep, Henry Ford bought the Wright's cycle shop and had it moved from Dayton to Dearborn!