Whats the real difference between a saddle height thats spot on and one thats just a hair off - is it really going to be the deciding factor between a podium finish and a trip to the hospital, or are we just splitting hairs here? I mean, weve all heard the old knee should be almost fully extended rule, but what about when youre bombing down a rocky trail and your knees are bent just to stay on the bike - does that rule still apply? And what about all the different types of mountain bikes out there - do the same saddle height rules apply to a cross-country hardtail as they do to a downhill full-suspension? Can someone explain to me why saddle height is so crucial, and what the actual consequences are of getting it wrong?