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  1.  
    I am doing a conversion build of a 70s Gitane w/ a layback seat tube and a funky obsolete French BB that desperately needs replacing. I am looking to throw some nice new components on it to improve the steel frame (i.e. IRO drivetrain), and looking to give it a new BB - hopefully one that isn't French. Anyone heard/done this? Thanks.
    • CommentAuthoreaglerock
    • CommentTimeJun 3rd 2010
     
    A lot of people here could tell you stories...

    https://velospace.org/forums/discussion/129/french-bottom-bracket/

    https://velospace.org/forums/discussion/1559/french-bb/

    https://velospace.org/forums/discussion/1633/80s-peugeot-bottom-bracket-length/

    https://velospace.org/forums/discussion/2412/can-a-phil-wood-bottom-bracket-fit-an-80s-guerciotti-frame/

    Remember that, obsolete or not, the bottom bracket is held in the frame by cups threaded into the bottom bracket shell. French BB threading is different from all the other threadings; you can't just pull the French cups out and toss others in. Sheldon sez British BBs (the only common system with rational threading) are too small; the BB cups won't engage your existing threaded BB shell. I've read that it's possible to retap a French (or Swiss) bottom bracket shell to accept a larger Italian bottom bracket.

    But that's going to be expensive, unless you're brave/knowledgeable/foolhardy enough to attempt it yourself - and you'd have to get the right tools even to try. Why would you do that when there are reasonable alternatives available?
  2.  
    Get a threadless bottom bracket from Velo-Orange. They're cheap and work great.
    • CommentAuthoreaglerock
    • CommentTimeJun 4th 2010 edited
     
    Posted By: peterabbitGet a threadless bottom bracket from Velo-Orange. They're cheap and work great.

    They're scary-ugly, with that two-toned anodizing; but it's a good idea, and you can move the BB to British/Italian/Swiss/Raleigh-threaded frames later on. It's in one of the links I posted above.

    I've also just found that Tange makes a sealed BB in French thread, available through Yellow Jersey.
  3.  
    Both velo-orange and the bike biz sell French threaded bottom brackets for about 50 bucks. Good luck with your build.
    • CommentAuthorGone
    • CommentTimeJun 4th 2010
     
    I threaded a vintage Motobecane 36X24F Italian with Campy thin wall cups and I use a Campy 68-P-110 axle. Very tight and works perfectly mind that Marinoni did the job.
    • CommentAuthorper.k
    • CommentTimeJun 4th 2010 edited
     
    I am perfectly happy with my velo orange bb ;)
    • CommentAuthorFlat Four
    • CommentTimeJun 5th 2010
     
    Been running a velo orange GrandCru bottom bracket on my Peugeot for almost a year and I love it.
    • CommentAuthoreaglerock
    • CommentTimeJun 5th 2010
     
    Posted By: per.kI am perfectly happy with my velo orange bb ;)

    Posted By: Flat FourBeen running a velo orange GrandCru bottom bracket on my Peugeot for almost a year and I love it.

    In each case: Threaded or threadless?
    • CommentAuthorper.k
    • CommentTimeJun 6th 2010
     
    definitely the threaded one for me
  4.  
    Posted By: Flat FourBeen running a velo orange GrandCru bottom bracket on my Peugeot for almost a year and I love it.


    I later stumbled upon this very BB and was thinking about going with it. I have no idea what year my Gitane is or even what model it could possibly be - should I just shoot the moon and hope it fits? Or are all French BB shells the same dims?
    • CommentAuthoreaglerock
    • CommentTimeJun 7th 2010
     
    Posted By: customfun50Or are all French BB shells the same dims?

    Up to about the early '80s, when the French framemakers finally started to face reality(!), almost all French frames used French-thread bottom brackets and French-thread headsets. Motobecane did some of their US export frames in French thread, and others in Swiss (same physical dimensions and thread pitch, but the driveside threading is reversed like British, so the cup doesn't unscrew from pedaling). Custom builders (AKA 'constructeurs') such as Rene Herse and Alex Singer might thread differently based on clients' requests.

    As for "same dims", yes; that's why French threading was a standard. It just wasn't the standard that won out in the long run. French BBs are threaded 35mm x 1mm - slightly larger shell, slightly tighter threading than British. French headsets/fork threadings are 25mmx1mm - slightly smaller diameter, slightly tighter threading than British. Because the headsets are smaller, the quill stems are also smaller: 22mm (instead of 22.2mm) and the handlebars are smaller (23.5mm/25mm, instead of 25.4mm/26mm). Pedal threadings are 14mmx1.25mm, instead of 9/16"x20tpi, so French-thread pedal holes can be tapped to fit British/Italian-thread pedals.

    Basically, the French standardized on metric measurements (millimeters), while the British standardized on Imperial measurements (inches). If the French had just had the sense to thread their bottom brackets Swiss-style, so the cups didn't loosen with normal use, their system might have won out, although the stem/handlebar diameters are pretty wussy. The combination of skinnier tubing diameters with the softer steel/aluminum formulas common in the French bike industry means that many French stems/handlebars are easily busted; AVA is notorious for this.

    The late, great Sheldon Brown, a fan of French bikery but a realist, has a whole page on monkeywrenching cheap and readily available British-standard parts to work with French frames.
  5.  
    Posted By: customfun50
    Posted By: Flat FourBeen running a velo orange GrandCru bottom bracket on my Peugeot for almost a year and I love it.


    I later stumbled upon this very BB and was thinking about going with it. I have no idea what year my Gitane is or even what model it could possibly be - should I just shoot the moon and hope it fits? Or are all French BB shells the same dims?


    If your really worried about wether its french or not, take it to your LBS and check it. They should certainly be able to tell you, plus if it turns out they are a Velo Orange dealer they could have what you need in stock.
  6.  
    • CommentAuthoreaglerock
    • CommentTimeJun 7th 2010
     
    You know, guys, if the cups say 35 x 1...it's French. Only the Swiss (and Motobecane, sometimes) used Swiss threading, and nothing else is 35 x 1.

    This is not rocket science.
  7.  
    I didn't realize there was a bottom bracket in place already. I skimmed the first few posts too quickly. I guess my post was more geared towards a situation where some one didn't know the year of the frame, and there was no bottom bracket already in place.

    ... but dude, really? you had to throw "This is not rocket science" in there? It seems to me, that velospace as much a place to nerd out on bikes as it is a place for people to learn. I don't see a reason to add that. Even rocket scientist might not know the thread dimensions and history behind french bottom brackets. It's a somewhat specific field of knowledge.

    Although, on a less agitated note, nice job laying it out on the earlier post. Very informative and concise.
    • CommentAuthoreaglerock
    • CommentTimeJun 7th 2010 edited
     
    Hey, if there are people out there who need to check BB shells for French-threadery, I bet I can scare up a spare driveside cup (the one that makes the difference) with which to test said BB shells. But as a general principle, if the frame's got a Frenchy name and a British BB doesn't thread straight in (it'll be too small), it's French. Proceed accordingly.

    Alternately, the Shimano UN-31/51/71 all have two adjustable cups, and will take Phil Wood cups. If you find one of those (bigger numbers are lighter, and have swankier bearings), you can swap Phil cups until you find the right ones (British/French/Swiss/Raleigh/ Chater Lea; Italian uses a longer BB).
    • CommentAuthorClinton
    • CommentTimeJun 8th 2010
     
    c'mon, SON. leave the cups, approximate b/b... lazer eye, chain line, AKA: low budget alley mechanic. take a chance... have two or three or seven bikes as a standby. also,listen only to Sheldon. all others are subject to speculation and self doubt. ride ON!
 
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