Re: Disc brake question
Marko's problem is a common one with regard to swaps from drum to disc brakes. As mentioned by several posters, this issue has to do with not having enough free play in the rod between the brake pedal and master. When your foot is off the brake pedal, because the piston in the master isn't all the way back at its "starting" point, pressure is kept in the brake lines and the calipers drag more than they normally do.
Residual valves are another (similar) subject. They keep pressure in the lines so that brake fluid doesn't bleed back into the master.... kind of important
with drum brakes because otherwise you'd be left having to pump up the brake pedal to enjoy short pedal travel. Not something you want to need to do.
On disc applications you'll see residual valves mainly if the master is mounted at a weird level, like lower than the calipers.
GM used a quick take-up master and caliper design years ago to keep rotor dragging at a minimum for increased fuel economy reasons, but that's a whole 'nother story.
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