Bicycle Mechanics - Re-cut BB Thread from French to Italian?

My wife brought home a Peugeot bike for $10. There is a problem with the crankset, so I'll need a new Bottom bracket. Unfortunately, the bike has a French threaded BB, which is hard to find and is generally very expensive (considering the cost of the bike). Someone on the Bicycling web site mentioned that it is possible to re-cut the French thread with Italian die (which is of larger diameter. Those BB's are commonly available. I know that this approach sounds crude, however, it would be the most economical longer term solution for me - and the risk is $10. What's your experience and/or recommendation with this respect? The shops seem to be unwilling to try to do it for me - any idea or advice?

Right now, until you fix it, the most you can lose on this deal is $10.00. Old, unused road bikes are a dime a dozen. I'm thinking that for much less than the cost of re-machining the bottom bracket you would be able to find another old bike in better condition.

Not every shop has the bottom bracket tapping tools that are required for this job. Everybody I know who has them, reserves the use of them to just chasing out existing threads of the same pitch. The tools are fairly expensive and they don't want to bugger them up working on a "junk" bike. The guys who are most willing to do this kind of work tend to be guys who have never done it before.

Most shops BB taps are just for chasing threads. To do it right you need to bore the BB for the italian threads and use a cutter that is made for making new threads. (It is about $50 just to sharpen my BB taps)

have you asked Sheldon (I can fix that) Brown? see his website first!!!!!!!!!!

Thanks 1oldRoadie. Sheldon Brown/Harris actually sell the french parts. I have three options that I could think of. One is to throw the bike away. Option two is to fix the bike to the original specification, but many of the moving parts are worn out, so I would have to get many of the old components replaced, and I don't actually like the old very heavy cranks and other components so much, and I don't really like to throw the bike away. So I am most likely going to take an option three, replace the drive train componenets with newer, lighter and better parts. I guess I'll end up getting Phil Wood BB, which can be adapted with rings to the French thread. I can then use Campy cranks, cassette, derraileurs... and have the old, un-appreciated bike with the performance I am looking for. Nostalgia, but not all the way. The Italian threading would save me the extra cost for the PW BB and be more "main stream" in the future. This is a hobby for me, not really practical, but I have to do practical things all the time. This allows me to enjoy activity without having to justify it's "sense" to the boss, government or to the wife. Too bad that this represents such a small opportunity for the LBS that it is really not interested in such business, but I understand....

Make it a fixed gear. You don't have to worry about shifters or freewheels. Unless the hub is heliocamatic a cog should spin right on. Use an english BB lock ring to keep it from loosening. Then respace and dish for good chain line. Keep the cranks for a period look. ( I looked and I have french and swiss cups collecting dust as well as cottered spindles) Keep or ditch the brakes depending on your confidence and how hilly it is where you live. You will have a french stem as well, might be hard to find if you need a different length.

Aw, man, Rev. Chuck beat me to the punch. I, too, would recommend making it a fixed gear or at least a single speed. Making it single speed would be least expensive since you can probably use the existing wheel and just spin on a single speed freewheel. I particularly like Shimano ss fw because they are quiet and inexpensive. After using a Shimano for a while I wanted a different gear. My LBS talked me into a "better" freewheel which cost about $40 compared to about $20 for the Shimano. I hate it! The Shimano makes no noise (the usual pawl clicking) while this "better" one is louder than anything I have ever heard. It may be "better", but I prefer quieter.

Anyway converting to ss will cost very little and is a lot of fun.

Upgrading as you describe would be really impractical. Believe me, I am a BIG fan of doing impractical things to bikes, but what you describe would also be quite expensive. Those clunky old cranks you describe have a certain elegance on an old bike. As far as the moving parts, you would be amazed at what a good cleaning, replacing the old (bearings headset, hubs, bb) and relubing will do. An old bike can be better than new. Replace the brake cables and housings and brake pads and you're in business. Replacing the der cables and housing and cleaning up and lubing the ders will work wonders, too, if you want to keep it a 10-speed.

O.K. You guys talked me into it, I"ll give it a shot. Last time I've ridden a single speed was my dad's bike many years ago. I'll see how weak I am I guess. I really appreciate your guys advice.

Come on now, kick it hard core. No freewheel, use a fixed cog. Only way to go!

I'd do it, but what about the widow and the orphans?

It's not so bad. I run an old Trek, 42/17 gears, tubulars, and a front brake(It is hilly here). If you keep the brakes you should be OK until you get the hang of pedaling all the time and the bike will remind you by picking you up off the saddle if you forget. The only real danger is turning to sharp and touching your pedal down, you will wet your shorts.

Two of my bikes (Capo and PKN-10) have Swiss-threaded BBs, and one (UO-8) is French-threaded. (The Schwinn is English-threaded, and the Bianchi is Italian, making me equal-opportunity with regard to BB shell standards.) I have accumulated a small collection of used metric BB cups, which I have mix-and-matched with various spindles to support different cranksets (Nervar Star, Sugino mountain triple, and Sugino Aero, respectively). I never pass on an opportunity to rescue a castoff Austrian, Swiss, German, or French (Carbolite 103, anyone?) frame, in case it has serviceable BB cups. Metric BB cups also show up from time to time on eBay.

English and French BBs have virtually identical (1-3/8" = 35mm) diameters, but different thread pitches (24 TPI vs 25.4 TPI = 1 mm). I have ridden the PKN-10 for several years with an English-threaded Sugino fixed cup force-threaded all the way into the BB shell -- I suppose one could apply the same technique by forcing an English-threaded adjustable cup into each side of a French BB shell. I am certain this does not meet the Master Mechanics Seal of Approval, but it has worked very well for me. (My fixed-cup trick is limited to Swiss BB shells, which share the English anticlockwise threading.)

I have also read about cartridge-style BB assemblies which clamp into the BB shell, without using the frame's threads. (One simply TIGHTLY threads one half of the assembly into the mating threads of the other half.)

It is possible to cut threads to Italian, but this process will wear the tool greatly. It is best to ream the inside diameter. A tap should not act as a ream. The inside diameter will need to be 35mm, not the 34mm it currently is.

There may be another option with the Stronglight bottom bracket. There is a model that uses two outer lockrings that tighten against the shell. This bb does not rely on internal threads at all.

The bottom bracket tapping process is seen at Tapping and Facing (http://www.parktool.com/repair_help/howfix_bbtap.shtml)

Originally posted by Rev.Chuck
It's not so bad. I run an old Trek, 42/17 gears, tubulars, and a front brake(It is hilly here). If you keep the brakes you should be OK until you get the hang of pedaling all the time and the bike will remind you by picking you up off the saddle if you forget. The only real danger is turning to sharp and touching your pedal down, you will wet your shorts.

Thats assuming you still have the ability to wet you shorts after the saddle attempts to become part of you permanent anatomy when you put a pedal down in a turn :D

Try www.cycleart.com for old bike components. Also, you may consider rethreading to Engish threads. I do like Stronglight BB system. It sounds like you have a good bike to train yourself up to be a wrench.

DieselDan, thanks for your tip, but I am having a problem with that link - the page comes out blank. Also, the diameter of the English threaded opening is 34.8mm, which is slightly smaller than the 35mm French thread, and it is cut in the opposite direction. How can I cut a hole which is smaller than the one already there? I am not sure that I understand your advice.

CycleArt dot com (http://www.cyclart.com/cgi-bin/miva?Merchant2/merchant.mv+Screen=SFNT) This one should work.

I'm just a bit off on the English threading. You'd have to ream the hell out of the BB to do so and you could end up trashing the frame. If the cups and races are still good, you just need new bearings. I've had success with rotery tools the clean and hone cups, cones, and bearing races. That website may have some old French BB parts.