I Have a Stronglight crank and BB that I salvaged from a Mercier (year unknown) that I am trying to use in this MB mixte frame (also year unknown)


When I removed the BB cups from the Mercier both sides have right hand threads. This is what I expected from my limited knowledge of "French" BBs. And it is what I expected when I tried to instal the bottom bracket in the MB. The threads on the non drive side are the same right hand threads on the cups I have but the drive side appears to have reverse left hand threads.

I now have to find at the least one Stronglight drive side BB cup and I need to know exactly what to look for.

Thanks in advance and I know I should have paid attention when this BB stuff was all explained before but I never thought I would ever find myself buried this deep in a couple of French bikes.

Left hand treads on the fixed cup with right hand threads on the adjustable cup + old (70's/early 80's) Motobecane frame = Swiss threading!. Not fatal, but it will not be that easy to find a new BB. Phil Wood makes cups for his BB cartridge but it will cost a lot of money. a few NOS Japanese (SR?) comes up once in a while at eBay..........also for a lot of money (close to a 100 bucks just for cups!)........I feel your pain, I have the same thing in my 84 Peugeot PSV.

Good luck building the MB mixte up. look like it will be a nice bike! Hope you find the BB for it soon.

Chombi

I ran an English BB in a Motobecane with Swiss threads. It was loose when I threaded it in, but it tightened down fine. I had no problems with it. You could give that a try.

An English cartridge bottom bracket can be forced into a Swiss-threaded shell. I wouldn't do it, but some have.

This one is a 75-76 and i used a Shimano sealed cartridge.Installation was fine and had no problems so far.