Classic & Vintage - Convert EF Schwinn to French Thread BB

I have a '74 Schwinn Sprint frame and a 3-piece Nervar crank off of a '73 Schwinn Sports Tourer. I'd like to use the Nervar set up on the Sprint. I can find conversion kits to adapt English thread BB's to the EF frames, but not French threads. Can anyone help?

Thanks.

furyus

If your Nervar crank came off a Sports Tourer its English threaded.

Really? It did indeed come off a Sports Tourer. I'm betting there is a thread somewhere showing me how to tell the difference, but what do I look for when attempting the swap?

Thank you.

furyus

The French crank makers provided English threads on their cranks for English and American bikes.

Thanks guys, I appreciate the help.

furyus

The French crank makers provided English threads on their cranks for English and American bikes.

Because even the French thought french threading was a lousy idea :lol:

Because even the French thought french threading was a lousy idea :lol:

I've always thought that swiss threading makes the most sense of any BB threading, nice even metric sizes and LH/RH thread. If the french and swiss had conspired to push swiss threading, it may well have stuck around longer than either have since.

But in answer to your question, yes, there is a conversion kit. It's about 15 buck as I recall and not too difficult to preform. Pastorbob knows his Schwinns inside and out. Ask him where to get them.

But in answer to your question, yes, there is a conversion kit.

Ashtabula to French threading? That was the OP's question.

I'm having trouble making sense of this thread. Why would you want to use a French-threaded bottom bracket with the adaptor? The only French threads you might find on a French crank are the pedal and extractor threads.

Maybe it's just me. It's early.

I'm having trouble making sense of this thread. Why would you want to use a French-threaded bottom bracket with the adaptor? The only French threads you might find on a French crank are the pedal and extractor threads.

Maybe it's just me. It's early.

The OP appears to be a newbie (at least to the forum) and assumed that the bottom bracket for a French crankset would have French theads. He neglected to take into acount the USA origin of the donor frame.

I've always thought that swiss threading makes the most sense of any BB threading, nice even metric sizes and LH/RH thread. If the french and swiss had conspired to push swiss threading, it may well have stuck around longer than either have since.

I only found Swiss threading weird because it is hard to find good quality BB's with the treading. Everynice NOS BB out there is either English or French and some Italian.. I never really looked into it, but does the threading direction on Swiss BB's avoid the tendency for loosening from rotational loads coming from the bearings against the cups?? Is that why they make more sense than other BB threading to you?

Chombi

The OP appears to be a newbie (at least to the forum) and assumed that the bottom bracket for a French crankset would have French theads. He neglected to take into acount the USA origin of the donor frame.

It's some of the reponses from the regulars that had me confused.

I've always kept the Ashtabula cranks and kickstands on my Schwinn road bikes because they look right and never creak or cause trouble. I found that the steel chainrings (even on my '64 Varsity and '62 Continental) are perfectly compatible with 9-speed chain (I used C9).
I did have to search extensively to find a few pair of the rare 1/2"-thread clipless bmx pedals, but now I can put my Supersports, Continental and Varsities up against the local Velo-Peloton and duke it out. I just wish I had an extra set for my '61 2-speed Traveler!

I found my 1980 PX10 to have Swiss threading, but when I first went to replace a bad bottom bracket I was thinking it seemed English because of the LH threading on the drive side.
As I installed a shorter, 113mm JIS bb to work with the (ISO) Stronglight arms, The alloy cups on the UN-71 replacement bb needed force to go past a couple of turns and I had to work both cups in with an 18" wrench, going back and forth a hundred times to cut the metric (Swiss) threads into the alloy English cups.
I was able to get the cups to seat nicely against the cartridge bb, and it should last at least 40k miles or forever, whichever comes first. I can't imagine it loosening from normal use. I had to really push on the cup tool to keep the splines from slipping out of the Shimano cup, but now the cups are fully home and the chainline is perfect for the 7-speed freewheel I'm using.


I only found Swiss threading weird because it is hard to find good quality BB's with the treading. Everynice NOS BB out there is either English or French and some Italian...
Chombi

http://www.bikeforums.net/showthread.php/images/misc/quote_icon.png Originally Posted by GrayJay http://www.bikeforums.net/showthread.php/images/buttons/viewpost-right.png (http://www.bikeforums.net/showthread.php/showthread.php?p=13758235#post13758235)
I've always thought that swiss threading makes the most sense of any BB threading, nice even metric sizes and LH/RH thread. If the french and swiss had conspired to push swiss threading, it may well have stuck around longer than either have since."

The Sports Tourer has standard 68mm 1.37" x 24TPI English thread BB shell.

The Ashtabula to 3-piece crank adapter sailorbenjamin mentions isn't necessary for a Sports Tourer, but is necessary for the Super Sport which came with a one-piece Ashtabula crank like the EF Sprint (the BB shell on Super Sports is larger than the shell on the Sports Tourer and isn't threaded).

Here's the TruVative BB adapter that converts bikes with Ashtabula BB shells to be compatible with English threaded bottom brackets.

http://i32.photobucket.com/albums/d7/k4drd/Bicycles/1973%20Super%20Sport%20CJ809208/TruVativeConversionKit.jpg

Here's the TruVative adapter installed on my '73 Super Sport.

http://i32.photobucket.com/albums/d7/k4drd/Bicycles/1973%20Super%20Sport%20CJ809208/CIMG5638med.jpg

I only found Swiss threading weird because it is hard to find good quality BB's with the treading. Everynice NOS BB out there is either English or French and some Italian.. I never really looked into it, but does the threading direction on Swiss BB's avoid the tendency for loosening from rotational loads coming from the bearings against the cups?? Is that why they make more sense than other BB threading to you?

Chombi

Yes, Swiss BB thread is LH/RH (like english). The NDS is identical to a french cup, the DS is LH threaded. 35x1mm threading just seems like a more rational deminsion than english fractional inch thread for a worldwide product. I suppose that the demise of swiss/french threading demonstated the clout of the US+British marketplace for bikes.

Aparently during the 80's some of the french manufactures did briefly switch to using swiss threading before abandoning it for worldwide compatibility of english.

I suppose if the Italian speaking cantons of Ticino and Grisons in Switzerland ever produced bikes, they would have developed a special LH/RH version of Italian threading.

I only found Swiss threading weird because it is hard to find good quality BB's with the treading. Everynice NOS BB out there is either English or French and some Italian.. I never really looked into it, but does the threading direction on Swiss BB's avoid the tendency for loosening from rotational loads coming from the bearings against the cups?? Is that why they make more sense than other BB threading to you?

Chombi

Not so much the rotational friction force, which is in the direction towards unscrewing the cups. The rotational force is really tiny compared to the precession force, which is in the other direction. That's why you really have to reef down on the fixed cup in French and Italian BB's- the precession really wants to unscrew the drive-side cup. Same thing with the pedals.