Originally Posted by
JohnDThompson
Spindle too short, and the chainring hits the chainstay.
Spindle too long, and chainline offset makes shifting suffer.
BITD, you could make small adjustments to "Q" (lateral pedal spacing) with different length spindles. Petite riders might like lower "Q", while duck-footed galoots (like me) might be more comfortable with more "Q".
As Bob says- that's gone by the wayside with modern two-piece cranks.