Brake pads are rubbing

[dubie]

I just installed the CPP power disc brake conversion on my 56 a couple weeks ago, but still have to run the lines and bled the system. I find that I can't freely spin the rotors without the pads dragging. I know this isn't normal but what's the cure for it? I know it's gotta be something simple seeing how every single part on this front end is new

Any ideas folks?

[Amorget]

Define dragging? Just like a light touch? If so, that is normal for a disc brake setup. Unlike the drum brakes they don't full retract. If you can spin them easily by hand, then it is probably correct.

[dubie]

I might get 1 full revolution out of it when I spin the rotor by hand. There seems to be continuous contact with the brake pads. Will that change once the piston starts getting used?

[Amorget]

If you get a full revolution out of it when you spin it, then you are good.

It won't change as they get used. There is nothing to physically pull the pad back off the disc like there is with drum brakes with the spring.

[meter swinger]

I haven't used the CPP kit but in my experience with new pads, rotors, calipers, they tend to drag and be very of a very tight tolerance. If the kit came with shims for the pads maybe try taking them off. When I did the brakes on 78 gmc recently the first set of pads I got (napa) would not even fit between the caliper and rotor, i went elsewhere and bought metallic pads and ran them without shims and had no issues. After a test run I would pull the wheels and re-check them to avoid any potential of warping the rotors.
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[mr48chev]

Originally Posted by dubie

I might get 1 full revolution out of it when I spin the rotor by hand. There seems to be continuous contact with the brake pads. Will that change once the piston starts getting used?

That's called normal for disk brakes. They have no way to retract them from the rotors except letting the pressure off so that they only have a little drag.

[OrrieG]

Discs always drag a little, that is why they are quicker and take relatively little fluid to engage. If your MC is near level or lower than the calipers you need to run back flow devices in the lines to keep the pressure up, they will not pump up like drum shoes.

[magicoolbus]

If I remember right for disc fronts and drum rears, you need a 2lb residual valve for the front and a 10lb for the rears when the master cylinder is equal to or lower than the caliper/drum. Lots of info on this on this site and others. When I did my conversion, the proportioning valve had the residual valve installed internally so I didn't need them. But on occasion, in stop and go traffic, my rear drums don't completely disengauge and there is a slight drag felt. I plan on installing a new set of brake shoe return springs to see if that helps.

[mr48chev]

Drum brakes will drag slightly if they are adjusted correctly.