BB spindle length.

[mac-highlander]

Generally a triple crankset needs a longer BB spindle than a double or a single, be aware also that there are 2 differing standards for BB spindles, JIS (Shimano) and European (Campagnolo) the taper (2 degrees)is the same but the Campagnolo one starts off thicker so doesn't really work. The last 4 builds I've done I cheated and fitted an HT11 or Ultratorque bottom bracket crankset. Deore Triple on the Raleigh 'Oulander' MTB, 105 double on the Raleigh 'Road Ace', Ultegra triple on the Raleigh 'Equipe' and a Campagnolo Centaur double on the 653 'TT frame'

Yeah it’s English thread and JIS taper