Originally Posted by FastFreddy
Two things that haven't already been said: (1) If you ride a lot both on and off road you really need a bike designed for each -- road and off-road have totally different demands; (2) Your gearing seems low for road use -- don't you "run out of gears" on even a slight down hill?
Good luck and don't let anybody tell you that commuting on a bike isn't cool.
On my stock triple gearing on the specialized hardrock, 42/32/22 11x32, I maxed out at some ungodly cadance (way way above 120rpm) and hit 40mph going down a tunnel with a tailwind and I stopped pedaling, tucked in, and continued till I hit 50. I usually hit ~120rpm (which is a pretty good cadance) going down the roadway of a bridge here around 32mph or so.
On flat ground, he should have no problem maintaining 25mph average speed on his mtb (which is insane for a regular commute, even on a road bike).
As far as the jerky brakes, the bike needs a tune up and maybe new pads.