Originally posted by riderx
??? Why ??? I've built quite a few single speed/fixed gear bikes and have never had to shorten the BB spindle. Use the middle chainring position of the crank and you'll be fine. On a geared bike the BB and crank are spec-ed to provide a straight chainline w/ the middle ring.
Why? Jonny T. was talking about using a single speed crankset, that's why. If he is swapping out a triple for a double or single, he'll probably want a shorter spindle.