Hot Rods brake problem

I am looking for a little advice. I have a 32 ford highboy, chevy powered etc, gm single piston disc brakes up front with big ford 11.25 drums in the rear. I have the 2 and 10 lb valves in place, a new master 1 inch bore, new rear cylinders and new rubber hose on the rear differential. Stainless lines up front. System has been bleed, good flow as well as the master. The issue is this, I have a firm pedal, press on the brake pedal and it goes in about 1 inch and then the brakes are fully applied, it stops on a dime if you hit the pedal hard. the issue I have is there is no intermediate brake, its either full on or not. Its not like you can just come to an easy stop with gentle foot pressure, you have to fully push the pedal to stop there is no slowing down. Hopefully that makes sense, just doesn't feel right. I checked the front calipers they seem to rotate pretty freely with little drag, I am wondering if they could be low drag calipers? can anyone advise me how many turns you can get after turning it by hand out of normal calipers verses low drag. Any other ideas how to check them on the car? I bought this car used and have fixed multiple issues, mechanical, electrical etc which had been done incorrectly but this has me stumped, the rear wheel cylinders were the wrong size, since corrected, changed the mc as I didn't know the bore size or how good it was. Any ideas would be appreciated thanks

 

To start, make sure the pedal travels freely and fully without any binding or interference by disconnecting the master push rod. Also, make sure the rear brakes are correctly assembled. What kind of brakes are these, as 11 1/4" are odd?

 

Disk brakes up front? Drums in rear. Did you make sure the 10psi residual valve is for rear with adjustable prop valve. And 2 psi valve for front? Wildwood has the in line kit. And you have brake under floor I'm assuming? No power booster?

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What is the thickness and diameter of the front rotors? Alternately, what is the pin spacing for the pins that hold them to the brackets?

 

Sorry. left out manual brakes, under the floor, brakes are 11 inch ford bronco rear end 9 inch, fronts are 5 1/2 pin ? not sure the car isn't here rotor is 11 inch I believe. I have the the 2 and 10 lb residual valves in place no proportioning valve, car stops straight . Went through the rear brakes, new hardware, new pins in the new cylinders etc. The pedal works fine, adjusted with clearance to the new master, set up for manual brakes. Thanks for the interest

 

That's an interesting problem,
What type of pad and shoe materials ?
The surface of rotors?

You'd figure if they work fine and stop on a dime with full pedal pressure that 1/2 pedal pressure would slow you down. Since you have no trouble bleeding and there's good fluid travel,,, just guessing here. To me it seems that the braking surfaces are slippery until the clamp load rises above the slip and then it's full on with the friction build up and slow down just being eliminated. Contaminated pads can do that

 

Is there a functional parking brake, and is the rear shoe drag correct?

 

the hand brake works and the rears have been adjusted, will pull the pads and see what they look like, rear shoes were good not much wear and no contamination. I keep thinking about the possibility of low drag calipers one or both, rotors look good no scoring or much uneven wear , will see what the pads look like maybe theres a clue their thanks. i think I will also disconnect the front line from the master and see what the pedal feels like, just don't trust the brakes in heavy stop and go traffic feline i have to leave a ton of room between cars. It would be interesting if the pads had gotten contaminated by a small leak of fluid. thanks

 

Next time you have the front wheels off, take a picture of any/all markings or numbers on the calipers, if there are any.

 

Oh, and what master cylinder is in there? Is it a proper disc/drum one, and do you have the lines hooked up to the correct ports?

 

Things I have found that makes your brakes act funny, assuming nothing is bypassing, leaking and are bled.

Master Cylinder bore too small

Loose not properly adjusted wheel bearings on a front disc set up will push the piston in too far (turning) and takes a lot of fluid to recover.

Disc calipers installed on the wrong side (left, right) will not bleed properly because the bleeder is not actually at the top of the piston area, yet you will get no more air when bleeding, but still have air in the piston area.

 

the one inch bore MC should be right for drum disc , calipers in the right position , lines are in correct position wheel bearings checked and correct thanks

 

Yeah, have a look at those calipers. Also, make sure that there are not any weird shenanigans going on with the pedal linkage.

 

Do you have a power booster on the system?

Disc brakes require approx 1450 psi to operate, drum brakes require approx 450 psi to operate.
even with a dual reservoir you will need a proportioning valve to restrict the pressure to the rear drums, you could very well be stopping using mostly rear brakes.
If you have a power booster, some complaints when adapting certain boosters with out installing the original rubber/neoprene washer/buffer the brakes do act as either all on or all off.

irrespective, if you have disc front and drum rear you will need a proportioning valve.