Pint-Sized Gnar Shredder
Join Date: Nov 2007
Location: Somewhere between heaven and hell
Bikes: '09 Jamis Komodo, '09 Mirraco Blend One, '08 Cervelo P2C, '08 Specialized Ruby Elite, '07 Yeti AS-R SL, '07 DMR Drone
Road bike fitting is a science. They can put you on one of those fit cycles like Serotta makes and determine, based on your structure and musculature, when you're the most powerful, when you're most efficient, and when you spin the best little circles, and decide what to prioritize based on what you're using the bike for. And they can take your imbalances and injury history into account and fit you accordingly.
Mountain bike fitting is an art. Sure, you can argue road bike fitting has some art involved, and I wouldn't disagree, but you have a lot more freedom in mountain bike fitting than road bike fitting. Discipline and terrain plays a large role, but even among people who are the same height, same inseam, and ride the same trails, rider preference and riding style also play a large role.