Singlespeed & Fixed Gear - 75 Motobecane...French or Swiss?

I just picked up (most of what I think is) a 75 Motobecane Mirage for $10. There is a "75" stamped into the seat tube (and it appears to match the pictures of such a bike on the web). My hope is to turn it into a fixie. It has a cottered spindle that I want to swap out (mostly because it doesn't have any cranks). Can anyone tell me if this year/model uses the Swiss or the French threading for the BB? The cups and cones appear to be in good shape and I don't want to put much money into it. Also, I'm not entirely sure that it has the correct spindle. Does anyone know the proper dimensions? Mine measures 137mm in total length with the left, middle, and right sections measuring 33mm, 57mm, and 46mm (assuming I measured them correctly).

Thanks for any advise you can offer.

if you removed the bottom bracket then you definitely have the answer. think about the driveside cup.

if you removed the bottom bracket then you definitely have the answer. think about the driveside cup.
Specifically, if the driveside cup (which is usually the fixed cup) has a left-handed thread, like a track hub lockring, it's Swiss or English. If it's right-handed, it's french. To differentiate between a swiss or english threaded cup, try and thread the BB lockring onto the hub. If it threads on, it's an english BB. If not the BB is Swiss.

The BB spindle length you'll need depends on your cranks, but generally the shorter the better. Cottered spindles are usually way longer than their square-tapered cousins because they go all the way out until they are flush with the outer side of the crank arm.

Thanks for the info. but I have not been able to get the fix cup off the bike. This may be a chicken and egg situation. I'll know what I have when I have it. Maybe I'll just flip a coin and put my back into it. I'll post the outcome if it comes out.

my guess is french,
but if you don't want to put a lot money into it and you are reusing the cups
does it matter ?

overall length of the spindle won't matter much or correspond to the length of a cotterless spindle,
but you will need match the distance between the bearing surfaces

75 is pretty early -- i am pretty confident that it'll be french, in which case you're looking at two right-handed cups.

an original 1975 bottom bracket fixed cup that hasn't been removed frequently is almost certainly going to be a total ***** to get out. I would really recommend using a special fixed cup remover from your local bike shop (make sure to tell them that it's french or they will probably turn it the wrong way). if you are budget deluxe, use the sheldon brown nut/bolt method.

75 is the seattube angle, not the year.

Did the bike have all of the components on it. If they are Suntour and Shimano you can find the year the parts were made for an approximate year of the frame if those components are original. (@ http://www.vintage-trek.com/component_dates.htm But, as el twe pointed out the 75 is not the year. Chances are it is Swiss thread which are tough to find. Later on 80's? I think they did switch to English.

Did the bike have all of the components on it. If they are Suntour and Shimano you can find the year the parts were made for an approximate year of the frame if those components are original. (@ http://www.vintage-trek.com/component_dates.htm But, as el twe pointed out the 75 is not the year. Chances are it is Swiss thread which are tough to find. Later on 80's? I think they did switch to English.

Awesome site! Always been wondering about my oldie Moto Mirage as well--the cranks that came with it (gotta be original, had big Motobecane branding) are stamped "77" on the inside which according to that site indicates the year. Mine is English thread, if it helps, but when I removed the BB that was inside when I acquired it, it was not cottered. So I don't know how similar our rides are.

The only components still on the bike are front, center-pull brakes (Weinmann 610, VainQueur 999) and the handle bars/stem. I see if they can lead me to a manufacture date. BUT, as Coelcanth pointed out, I may not need to worry about taking of the fixed cup if it's usable. I just need to find a spindle with the correct middle length.

Thanks for everyone's advise. I've only got $10 in this but I'm having a great time just learning!!!

Specifically, if the driveside cup (which is usually the fixed cup) has a left-handed thread, like a track hub lockring, it's Swiss or English. If it's right-handed, it's french. To differentiate between a swiss or english threaded cup, try and thread the BB lockring onto the hub. If it threads on, it's an english BB. If not the BB is Swiss.

The BB spindle length you'll need depends on your cranks, but generally the shorter the better. Cottered spindles are usually way longer than their square-tapered cousins because they go all the way out until they are flush with the outer side of the crank arm.

hey i was trying to teach a man to fish here, and you waltz in and give him a fish sandwich!?!

hey i was trying to teach a man to fish here, and you waltz in and give him a fish sandwich!?!
It would have been giving him a fish sandwich if I handed him the proper bottom bracket and installed it. Your "teaching a man to fish" was just grunting and pointing at a fishing pole.

METAPHORS RULE!

It's most likely French. Swiss didn't really get picked up until the late 70's. My '78 Motobecane has Swiss, and I believe that was a year or so after the manufacturer introduced it into their frames. If it is Swiss threaded, then you have very few options for a new BB. You can pick up some Swiss threaded cups from Phil Wood for $50 and pop them onto a Shimano UN-72 BB (I think a 71 works too), or go with an ugly threadless BB.