What brake set-up (meaning what size rotors for front and rear) would you put on an all-mountain bike?

Question

hydraulic or mechanical?

Answer 1

Most forks on an all mountian bike should take up to a 200mm (8 inch) rotor in front, and probably a 7in at the rear.

It depends also on your weight.  If you're like 130-150 lbs, probably you could do fine by 6in in both front and rear, but if you're heavier, you could use a larger rotor in front.  I'm like 230 lbs and run a 8 inch rotor in the front, and a 6 in at the rear.  Your really only need the huge stopping power at the front, and use the rear to prevent skids.

Hydros are usually a lot better than mechs.  It's not the sheer power, but usually hydros have better modulation than mechanicals.

Answer 2

There are very few bikes that have adjustable braze-ons or brake  bosses. Basically you're stuck with whatever the frame is designed for.

As far as mechanical vs hydraulic, go hydraulic for dh, mechanical for everything else.