I recently bought a used 2008 Cannondale Bad Boy Ultra from a colleague. The bike is 3 years old, but basically new (he said he's ridden it only about a dozen times, and by the looks of it that's true).
The Bad Boy has Avid BB5 mechanical disc brakes with 160 mm discs. Initially, their brake power was abysmal, comparable to the side-pull brakes of a cheap bike from the 60s or 70s. I took the pads out, and they had a slight coat of rust on them (I suppose that the discs got a bit rusty, and braking transferred the rust onto the pads). To give you an idea, it was absolutely impossible to get the rear wheel to skid, even when leaning forward on the bike and squeezing the brake as hard as possible.
I then sanded the pads until they looked good again, and also (lightly) sanded the discs and cleaned them with alcohol. This improved the brake power a bit, but I'm very disappointed.
I'm not expecting to get the same braking power as from the (much more expensive) hydro brakes on my MTB, but it's still pretty bad. I cannot get the rear wheel to skid when sitting on the saddle even when squeezing the brakes like crazy (it's not my hands, I'm pretty fit), and the front brake isn't any better. In comparison, the side-pull brakes on my road bike (105) are at least twice as strong.
Is this what I can expect from BB5s, or are they just crappy brakes? I kind of expected "better than road bike" performance from discs; are the brake pads ruined, and should I change them? Or should I upgrade to hydraulic disc brakes?
Money isn't so much of an issue, so getting some Juicy 3s (or something in that class) wouldn't be out of the question, but I don't feel I need hydraulics for what's I effectively use to go around town and short tours. So if possible I'd just make the BB5s work somehow.