Quote:
Originally Posted by Ecky
I'm almost certain discs have the most parasitic loss. They generally don't have a way to retract the pads from the friction surface safety braking.
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If adjusted right, I suspect disc and drum are very similar for parasitic losses. For long term issues and such, I'd say disc is more likely to cause a drag over drum. Normally drums "go out of adjustment" and you have to press the brake pedal farther for the rear shoes to touch the drum. When adjusted up, they should just barely have resistance.
Disc brakes on the other hand sometimes do have a spring to push the pads out a little, but the slides need to be in perfect working order, good caliper pin slides if it's a caliper with pistons on one side. I'm not sure how the 4 and 6 piston calipers are setup for the return system, but my Lexus LS400 front brakes have a spring that clips into the pads to help seperate them a little after braking. Here's a pic of the little springs, I suspect some mechanics would just throw them in the trash since they probably don't do a whole lot. The brakes are pretty undersized in that car too. I swapped the front rotors and clipers with bracket out from a 94, around 1 inch larger disc. It helped a little with braking, but it really needs a 4 piston caliper or similar since it's a large car. My prius on the other hand has very responsive brakes... did I mention the LS400 is 4 wheel disc, and the prius has rear drum =).
