Front Brake Drag

[lazypineapple]

ive got about 1500miles on my 52 now.
it has a MustangII front end with drums on rear.
Booster is under the floor stock location Blue residual valve on th front, red on th rear..
Pedal and braking are great.

How much should these fronts drag?
to me they seem to drag alot.
with it jacked up
you can turn the wheel my hand with much effort. no free spin,
you stop turning,
it stops.
with wheel off you cannot turn rotor just by grabbing it and trying to turn.Very Hard to turn

I seem to be getting alot of brake dust on my Wide Whites.
Rotors are glazing over.
i have even smell brakes when on Hiway sometimes.

does all this sound normal, for this set up?
or maybe a bad residual valve?
do i really need a residual valve?

thanks

[mechanixman]

It definitely does not sound normal.
Do you not have a residual valve on there right now?

[lazypineapple]

I have the residual valves installed. blue front,red rear.

Originally Posted by mechanixman

It definitely does not sound normal.
Do you not have a residual valve on there right now?

[Rufton]

I don't use a disc residual pressure valve if master cylinder elevation is above caliper.
My rotors spin easy by hand and work great.
Fluid change is easy because I only have to gravity drain.
Tempted to remove residual valves from drum systems to facilitate fluid change.
Last rebuilt drum master cylinders I bought already had residuals deleted but I installed OEM residual I already had.

[mechanixman]

That's another good point. Is your MC mounted in the stock location? or did you put it up by the firewall?

[mr48chev]

According to the sources I checked you have the residual valves on correctly as they show blue 2 lb red 10 lb residual pressure.
It could be that or it could be that the piston in the master cylinder isn't always clearing the port between the reservoir and the cylinder it's self. That would probably happen if the push rod was too long or adjusted out too far.

Another thing, do you have a working return spring on the pedal to bring it back up to the top? If not the pedal may be putting a slight pressure on the brakes by it's self.

[G&R's57GMC]

Are you sure that the M/C is for disc brakes ?

Are there any tight bends in the front flex hoses ?

Is there free play in the P/B to M/C rod ?

Are the calipers free to move on the slides and are they lubed ?

[_Ogre]

i set my mc up and pulled the cab
when i put truk back together the brakes were dragging
between new body mounts and reassembling the sheet metal my pedal was pushed down 1/8''
that's all it took to make the brakes drag

i removed the bolt between the mc and the pedal to see that it was depressed

[lazypineapple]

Mech,
M/C is under floor.

Mr48,
The rod play is correct,
But I do not have a return spring. I have noticed the weight of the pedal resting on the M/C and i reach down and pull it up.
But the brake still drags,
I will add a return spring,

G&R,
yes on the M/C for Disc. with a Disc/Drum portioning valve
Yes on rod FreePlay
flex lines are good , no tight bents or kinks,
fresh calipers are all lubed up.

Orge,
thats was one of my first cks was a loaded M/c pedal


Me thinks its the residual valve.
if i break the line loose at the M/C the front brake still drag and no fluid gushes out.
But If a crack the line after the residual valve I get relief.

while under it tonight
I also noticed that my M/C and Front Calipers are dam need level to each other.
measuring the lines at the M/C to the floor are the same height ,
as the center of the caliper puck.
so Im thinking of removing the front residual valve.

[G&R's57GMC]

If you have a correct disc /drum M/C it already has the proper residual valves built in.

This would keep a slight pressure in the line to the front and having a inline residual valve this would load that valve thus increasing the pressure to the front calipers.
Same would happen to the rear drums.

The aftermarket M/C may not have them. Thus the need for an inline valve.

[solidaxel]

I don't think RV are accumulative. 2+2=2
There should only be 2# of drag on the front rotors with the RV, sounds like you have much more than that.
can you leave the RV out of the line and try it without a RV

[lazypineapple]

its a CPP Booster M/C Pedal Assembly.
I'm changing my front springs, once i get it back together i'll try it without RV

[lazypineapple]

I took out the residual valve , bled, and adjusted rear shoes. Added pedal return spring.
Brake pedal feels fine.
Pedal is a little different, not as firm,not as high. But good.
Front brakes don't drag.
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[Rufton]

That sounds good.
I'm curious of no return spring effect.

[OrrieG]

Without the spring the MC was probably not uncovering or covering the front port in the MC which kept pressure on the pads. I had a similar issue, that little bit makes a difference.

[Rufton]

Some vehicles have a neutrally balanced hanging pedal and rely on MC internal piston springs to return pedal to up position mechanical stop. When swapping MC the pedal return stop needs to be confirmed to avoid loosing pedal to MC interface and for comfortable pedal free travel. I suppose the older truck pedals put weight on the MC which may overpower MC internal springs? Feel free to ignore if clear as mud

[lazypineapple]

The return spring had nothing to do with my brake dragging.
The RV was applying too much pressure or the R-pressure is not needed.

This floor pedal design was definitely always applying pressure to MC
It's a huge pedal assembly. So a spring is needed.
You could pull it up with your hand, pedal would stay up till next brake.
I'm only talking about 3/4"

Now if I could get the hard pedal back without a brake drag.
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[Rufton]

Brake line air is pretty good at hiding if there are unusual bends.