1 ton discs...

[NotMatt]

Finished my brakes tonight... Dual piston Ford D60 calipers up front, half-ton GM front calipers out back, '86 E-350 master cylinder on a stock '91 wrangler booster. The fronts run from one solid line down to the axle, then hard lines out and stock F-350 soft lines to each caliper. The rears are stock chevy soft lines up to the frame on each side, with a single hard line back to a T in the rear tub.

I figured I'd start simple and run no prop valve and see how things felt. I'm happy with how the brakes operate right now... rears lock up at the same time as the front testing them out in the snow-covered street. After I wheel it some I may add an adjustable prop valve for the rears if I feel it needs it.

However, the pedal is still very spongy after bleeding and bleeding... I bench bled the MC, then started from passenger rear to driver's rear, passenger front, driver front. I'm pretty convinced I got all the air out... I get a nice solid stream out of all four calipers.

Opinions? Do I need a bigger/better booster (I believe this is a single diaphragm one vs. the later dual diaphragm). Do I just need to pump the **** out of them and see if I can squeek out a little more air?

 

[CHOP SHOP]

Are any of the calipers on upside down? Like with the bleeder on the bottom of the piston instead on top where it belongs.

Just a thought.

 

[NotMatt]

Are any of the calipers on upside down? Like with the bleeder on the bottom of the piston instead on top where it belongs.

Just a thought.

Nope, haha. I'm not the sharpest tool in the shed, but I know that bleeder needs to be on top.

 

[ain'tstuckjustresting]

I would think too small of booster would result in a stiff pedal and poor braking, really sounds more like air in the system. When you mash the pedal down does it bleed down or is it solid?

 

[NotMatt]

I would think too small of booster would result in a stiff pedal and poor braking, really sounds more like air in the system. When you mash the pedal down does it bleed down or is it solid?

Hmm... "spongy" is the best way to describe it... I didn't think of holding it down for very long to see if it would drop and further. I'll have to play with it some more tomorrow night, drive it around the block some and stomp on it and then bleed it and see if I get any more air out.

 

[ain'tstuckjustresting]

Spongy is either air in the system or a bubbled rubber line.

 

[jeepmauler]

Sounds like air....keep bleeding.

When you get that setup dialed.... your gonna have killer brakes

My old buggy had a boosted Corvette M/C with half tons and it would do stoppies. The 1 tons up front are gonna be sick.

 

[benw1]

Do they firm up if you pump the pedal once or twice?

 

[boardbysled]

Do they firm up if you pump the pedal once or twice?

This.

Maybe a bad master?

 

[Gibby1]

Is the master is designed for a drum rear. If so, it simply cannot push enough fluid for the rear discs.

This is an issue that I have with my brake. I need to change to a 4 wheel disc master from a stock chevy master. Even with a proportioning valve, I couldn't get the brakes to work like they should.

 

[Jim1]

I'm guessing it's the booster, but only because everything you're using besides the booster I've used on my Bronco and the brakes are awesome with 44" tires on a ~7000lb rig.

The master cylinder will do just fine with GM 1/2 ton calipers in the rear.

 

[boxboy]

on my jeep I was using the same master, same booster, and same rears but I also ran the 1/2 chevy in the front woth no issues but I also installed a prop valve. I would put a couple miles on it using the brakes then blead them again it could just be a caliper binding up and you just need to work it free... but I did have to grind some on the mounts so the calipers would work smoother.

 

[zukkev]

Pumping the **** out of the pedal will only cause the fluid to airiate (sp?)...1 or 2 pumps max at moderate pressure, then hold while bleeding the line....
How's the pedal height at full brake application???

 

[CHOP SHOP]

need to pump it up and then stand on the pedal and see if it drops at all slowly at all.

Maybe a leak ina fitting or line that is seeping/sucking.

 

[NotMatt]

Yep, found a small leak in my rear hard line fittings. It's cold in the garage right now and I don't have motivation to start a fire and fart around with it tonight, so tomorrow it should be all fixed up.