Originally Posted by 79pmooney

The BB is the one contact point I cannot change. Seats are east to move in all directions except side to side. Likewise handlebars. I spend 100% of my rides with my feet rotating around the BB in perfect circles. On a big climbing day, I might spend 20% of my ride not even touching the seat. I've been known to ride miles at a time no-hands. I don't track seat to handlebar, partly because I put the handlebars on a line that is a near constant distance from my shoulder. (Actually an arc, but a line is very close for small changes and fart easier to document.)

I think of the "triangle". BB to seat, BB to line for the handlebars and seat to that line. I rotate that triangle to match what kind of riding I plan to do on that bike. For comfort, leisurely riding, it rotated back. For fix gears that will be ridden upwind, forward. I see the BB/seat relationship like a car's crankshaft, pistons and cylinders. That relationship is exact and never changes (outside a major engine re-build) but you can tip the entire engine anyway you want and it doesn't care. (Airplanes fly just fine upside down.) Everything revolves around the crankshaft. It makes little sense to pick any other place as a reference.

Ben