Hi there,

Anyone know if a 49D set of SL chain rings could easily be mounted on a 5-pin cottered crank set? I'm trying to get this onto my 1970s Motobecane, and am not sure if I'll be able to make it happen.

I mean does one cottered crank fit onto any three piece BB/Spindle?

Does anyone know what 5-pin cottered cranks I could find, that look and function well without spending too much?

Thanks!
Ash

If I understand correctly, and you currently have a three-arm cottered crank, you may as well just buy a whole new Stronglight crankset and BB and only have to deal with cotters once. IMO, this would be more easily user-serviceable and may be an opportunity to upgrade your crankset.

Many cottered cranks were produced with a 50.4mm bcd, it was a standard size in the 1940's and 50's. Any of them would be compatible with 49d rings.

As noted above, the 50.4mm 5-pin design was common and interchangeable among many brands. Cottered BB spindles do come in a variety of diameters, though, so it is not a foregone conclusion that any cottered spindle will work with whatever 5-pin arm you find.

Is there a compelling reason to use a cottered crank? By the 1970s these were only found on relatively low-end models. A cotterless 49d or even a TA Pro-5 would work fine on your Motobecane.