Bottom bracket size for Vintage Cannondale M300

[rsadventurer]

I have a vintage Cannondale M300 that I am trying to find the right size bottom bracket for. I know it is an English thread with a square 68 mm spindle, but I cannot figure out the correct spindle length. The 122 mm spindle is not allowing for the triple direllier to work properly. Does anybody know what the right size bottom bracket for this bike is? Thanks

 

[Ajax Bay]

The 122 mm spindle is not allowing for the triple direllier to work properly.

In what way is it "not working properly"?
Have you installed a 122mm spindled cartridge BB, then? Assume the old one is absent. Have you changed the chainset?

 

[T4tomo]

The spindle length is dependent on the chainset used, so if you have changed the chainset then you may need to change the BB too.

work out how far the middle ring is off centre to the centre of the cassette, and add / subtract from 122mm.*

* I cant remember if you double the difference or not, I think a longer/ shorter BB just sticks out more / less at the drive side, but I might be wrong.

** the is also the issue of ISO and JIS square tapers and a crankset will sit further inboard on one from the other.

*** If you your are simply refitting what was on there the the original length BB should still match the crankset, you might just have not position the front derailleur correctly?