Classic & Vintage - Peugeot & Motobecane parts compatibility

I have a nice 1982 Peugeot 5-speed city bike, imported from Germany, 100% stock, Carbolite, cottered cranks, 700c aluminium wheels, chrome fenders, plastic chain protector, chrome luggage rack, generator and lights, swiss BB threads, and a semi-moustache handlebar. It rides very nicely. I found a old beat up Motobecane 10-speed from the mid 70's. Question: Will the handlebar stem and square-taper spindle switch over? I'm pretty sure a Moto that old has French-thread BB so I'd like to just switch the spindle cranks and chainrings, effectively making my bike a 10-speed. I would also like to switch to drop bars. Thanks for any info!

Best info for the stem is to use a metric micrometer and measure the diameter of each stem . I would hazard to guess that they would be the same size, 21.9mm comes to mind, but I could be wrong. Measure the width of the bottom bracket shell of each frame. If they are the same then there is a good possibility that the cups are both french threaded on both bikes.

I would guess that both stems are French 22.2mm diameter, but given that you have both bikes in hand, it's easy enough to try the swap. Same goes for the BB spindle. I could imagine that if one BB is setup for loose bearings and the other for bearings in a retainer rim, you might have issues, but easy enough to try and swap spindles. If you swap the whole assembly, that 70s Moto BB is likely Swiss threaded as well, but if it's French, the threads-per-inch are the same, I believe. The Swiss fixed cup is a left-handed thread while the French fixed side is right-handed. That's something to keep in mind when muscling those suckers off.

Neal

I would guess that both stems are French 22.2mm diameter, but given that you have both bikes in hand, it's easy enough to try the swap. Same goes for the BB spindle. I could imagine that if one BB is setup for loose bearings and the other for bearings in a retainer rim, you might have issues, but easy enough to try and swap spindles. If you swap the whole assembly, that 70s Moto BB is likely Swiss threaded as well, but if it's French, the threads-per-inch are the same, I believe. The Swiss fixed cup is a left-handed thread while the French fixed side is right-handed. That's something to keep in mind when muscling those suckers off.

Neal

Thanks! I actually don't have the bike just yet, hence the question. I'll pick it up this coming weekend.

I would guess that both stems are French 22.2mm diameter I would have guessed 22.0mm for the Motobecane.


I could imagine that if one BB is setup for loose bearings and the other for bearings in a retainer rim, you might have issues, but easy enough to try and swap spindles. It is trivial (and strongly recommended) to replace a retainer cage with 11 loose 1/4" balls.


If you swap the whole assembly, that 70s Moto BB is likely Swiss threaded as well, but if it's French, the threads-per-inch are the same, I believe. Yes, both systems are 35mm x 1, so the adjustable cups are identical. I don't know when Moto changed from French to Swiss, but it was several years before Peugeot finally did. What I know for sure about French Peugeots is that 1974 and earlier were French-threaded, whereas 1980 and later were Swiss-threaded. I don't know about the in-between years or about Moto.


The Swiss fixed cup is a left-handed thread while the French fixed side is right-handed. Correct.

French stems are often cited as being 22.0 mm but I've found many to be a bit less. Curious, I recently checked my old Sutherlands Handbook (1st.ed, c.1974) which in fact does note 21.9 mm as being typical for a French quill diameter. A French stem's handlebar clamp diameter is also a tad smaller: 25.0 mm, rather than the common 1" (25.4 mm) found on most vintage (non-Italian) bars. You can either sand down the bulge of 1" bars or enlarge the opening of a stem if necessary, to make anything fit. And, in my experience, a 1" stem opening will most often clamp down sufficiently to grip French bars without adding a shim... [but use your own judgement here].

I believe it was Sheldon Brown's website which noted that sometimes it is actually just the top locknut of some French headsets which is narrow. I did find this true on at least a couple late 70s French bikes. So, You may want to check the actual inner diameter of your steering tubes to see if perhaps a 22.2 quill stem might fit into the fork. If that is the case, the easiest fix here would be to simply enlarge the opening of that single locknut. Of course, you can also sand down the base of a 22.2 quill stem til it fits.

I think Peugeots lagged behind Motobecanes in changing over to Swiss bottom brackets. I recently overhauled a mid-range Peugeot (P-7 ?) Carbolite frameset from around 1982 which still used French threads on the bottom bracket.

I'd proceed with caution when trying to remove ANY of them because too often owners (or mechanics) would eventually just slop a bit of locktite on the cups out of frustration - to prevent the inherent tendency of the French bottom brackets to un-screw their fixed cups (because of the friction of the ball bearings counter-rotating against the cups). ~ Yes, another of the many reasons why the wrench-flats on French fixed cups are often found in such damaged condition. ~ Have Fun!

Thanks for your help, everyone!:)