I have a '70 Barracuda with the factory KH? disc brake setup. My problem is the brakes have always dragged, like when the car is on jacks it tates a bit of effort to turn the front wheels. I have fitted new pistons, seals etc in the caliapers, new pins & rubber bushes they slide on, I have even replaced those strange little spring things on each pin. The wheels spin very freely without the caliapers fitted & the wheel bearings are new & adjusted as per the Service manual.

Any ideas?

If the car is booster equipped?,...you made need to adjust the pushrod coming out of the booster, that is located behind the master cylinder, as it may be too long resulting in residual pressure being excerted on the master's piston in the bore, resulting in front pad engagement, generally .060 (1/16") clearance between the end of the master's bore and the tip of the booster's rod is acceptable,...this usually occurs when an individual changes masters, as they vary in tolerances during assembly

Mike

Cheers Mike

Yes this car is factory boosted & has had a new master cylinder although I thought the brakes dragged with the old one too.

How do I check this clearance? do I split the Master cylinder off the booster, measure how far the pin protrudes & measure how far in it's seat is on the master cylinder?

Thanks, Kevin

as long as you can see through the brake fluid, you can look in the hole in the bottom of the rear resevior.
with a bright enough light, you can see the piston in the master.

I just stared at it when I pressed the master flush.
if it moved, dial back the adjustment. if it didn't dial it up till it hits. Aftermarket booster, so not sure if a factory would have that.

but that being said, disc do have drag. probably won't get more than half a turn if that if you spun it and let it go.

Either look into the fluid as said or undo the M/C mounting nuts & pull the M/C forward some or open a bleeder & turn the wheel/rotor & that'll tell you if it is a pushrod adjustment (psi) problem. As said discs always have some drag & the Q is how much do yours have? I just replaced the 74 A single piston caliper on one side when I had that problem & the new (rebuilt) one had way less drag but as you know the 4 piston ones ain't cheap

If you still have the original "flex" lines from the body to the caliper then replace them. They start to get really restricted and don't allow the caliper pistons to draw back.

Replace the factory springs with small coil springs. This fixed the problem on my car.

Rick at Mopar action recommends tacking those clips off, that they cause dragging. The other style of caliper doesn't use them.

If you can't spin the wheel after sitting for say 15-30 seconds, then something is keeping pressure applied

One other thing to check. Check the "ways" on the spindle, the part that the calipers and the pad ears ride on. After enough miles and braking actions they can get indentations. I found that on my Neon which wears the pads at an angle and prematurely.

Make sure your master cyl. is for disc brakes and not drum brakes. Drum brake masters have residual valves that keeps some pressure on the caliper. Ask me how I know.

if the calipers are new, then i agree with the above posts.

if the calipers are old, original, never been rebuilt... you probably need to rebuild them.

lots of rust builds up inside calipers and brake lines over time. brake fluid absorbs water and your internal parts will rust eventually. the only way to avoid this is by changing your brake fluid every year, even if you only drive 5k miles or something.

the cylinder walls should be honed as well.

after a while the caliper pistons dont move in and out as easily as they should.

Cheers everyone for your replys

The sliding surfaces on the caliaper & mounting baracet are all smoothe & clean, the caliapers have been stripped, cleaned, new pistons, seals etc

Quote:

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Make sure your master cyl. is for disc brakes and not drum brakes. Drum brake masters have residual valves that keeps some pressure on the caliper. Ask me how I know.

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How do I tell which one I have?

Thanks Guys

Manual 4 drum brake master cylinder.