I'm looking at adding some Avid disc brakes to my Fox F90 RL fork. Avid's product literature recommends not putting bigger than 160mm rotor on a cross country fork. Why the hell not? I know it will fit on there, so what's the problem? There are some extremely steep hills around here and the extra stopping power would be lovely.
I'd do 160 mm in the back... so, what's the problem? Is this just a weight-weenie / bike fashion faux-pas thing, or is there a practical reason why 185mm rotors = lose on an XC fork?