I have a square taper bottom bracket. How can I tell whether it is a J.I.S. or ISO taper with a minimum amount of disassembly?
FWIW, it's a Ritchey from 2004. However, it would be nice to get answers that apply to other brands as well.
The width across the narrowest part of the flats (end of spindle):
JIS = 12.65mm
ISO = 12.33mm
I can't find anything that states exactly what size the taper goes down to either, so you would need a known JIS/ISO to compare with. Other sources conform they are the same angle though. Minimum disassembly will be taking off one crank.
If its the length of the taper that matters, let measure that.
JIS = 16.96mm
ISO = TBD