Lets talk brakes and proportioning valves

[broncomitch]

I'm running full hydro steering ,Chevy hydro boost, duel piston ford calipers up front and the normal Chevy disc brake conversion on the back with a CNC cutting brake for the rear only and I'm using the stock early bronco drum-drum proportioning valve.

My brakes have always sucked and the proportioning valve is the only part on the braking system I have never messed with and wondering if its cus of that.

I have not blead my brakes all the way cus i have not plumed in the cutting brake yet (waiting on shifters) and I can already tell that the hydroboost is a huge improvement but I'm Wondering if I should ditch the proportioning valve and plumb the lines together? Or Get a disc-disc proportioning valve.

I'm sick of having crappy brakes and want this thing to stop the best that it can so I'm Also thinking of getting drilled and/or slotted rotors and was wondering if anyone knows of a good and or cheap set, I found some on summit for the front that I think will work but nothing for the back.

Front is a 88 ford kingpin dana60 and the rear is '73-'87 3/4 ton, 4x4, Chevy front Calipers & Rotors
Both are 8 on 6.5 bolt pattern

Now, obviously this is not street legal any more and is a dedicated rock crawler and the most it will see is 50mph.

Thanks

 

[surfer-b]

Well all I can say is this, I did the chevy conversion on my 74 and used the stock H-block, the brakes really wrk good, no probs at all and do not need much pedal pressure, it feels more like a modern brake system. I have my 76 which is all stock and all new everything except the p-valve, and all is the same as the 74 except for the calipers and H-block/P-valve and I really have to put the pressure on these to get them to wrk like they should. Sometime I am gonna swap the P-valve for one I pulled off of a BII, which had unbelievable brakes, and see if this make a diff. So my take on this is the 76/77 P-valves are very restrictive I cant say this for sure but I cant figure anything else that it would be.

 

[SpareParts]

Mine sounds similar to yours....

79' Lincoln dual disk master cylinder
79' Lincoln Hydro boost
79' Lincoln Saginaw PS pump, upgraded by West Texas
88' D60, dual piston calipers
80' 14 bolt, Chevy Impala calipers
Wilwood adjustable prop. valve

Mine will lock up 40's at hwy speeds if you stand on it...or crazy enough too. The brakes with the hydro boost feel kind of soft, until you press them further and then they really start to hold well.

 

[Apogee]

The drum/drum "proportioning valve" is actually just a distribution block and has no proportioning functionality, so unless it has a serious corrosion issue internally blocking flow or something, then it's probably not the problem. That said, what is the problem? It sounds like you have low brake torque and possibly a poor pedal, but it's not clear from your post.

As for drilled & slotted rotors, that's generally blingy aesthetics and marketing, so swapping out rotors probably won't change much if anything with respect to performance. MC bore size, booster function, pedal ratio, effective caliper piston area, pad compound and rotor diameter are what determine your overall brake torque and pedal feel.

 

[stock1970]

yep, slotted and drilled are more for high speed racers that generate tons of heat or hauling vehicles that ride brakes down mountain roads.. I would think.

 

[rustbucket]

Bleed the brakes! Can't expect good braking without doing this. Also, make sure the bleed screws are pointing up.

The drilled and slotted rotors, as was mentioned, are for high speed applications. Their purpose is to allow super heated gasses to escape from underneath the brake pads. During high speed, these gases can keep the brake pads from making full contact with the disk. There is really no purpose for them on a trail rig.

 

[SpareParts]

They would look cool...but not needed.

 

[broncomitch]

Won't bother with the slotted rotors for now sense my stock ones are bran new.
More for looks and so far what I have found is sometimes there the same price as stock style rotors.

At the moment the only problem I am having is air in the brakes.

Witch I'm not going to fix till I get the cutting brake plumbed in...I'm just wondering what I could do to make my brakes as good as they can be.


Anyone have any special tricks to bleed the brakes?
I remember reading a rat rod mag that was talking about putting a valve stem on the master cyl cap where the breather is and hook it up to the compressor that has a regulator on it.

 

[70_Steve]

Anyone have any special tricks to bleed the brakes?

The last several years I've just "gravity bled" my brakes. I use a length of clear Tygon tubing that fits tight overtop the bleeder. The other end goes in a coffee can. Open the bleeder and you can watch the brake fluid come out of the bleeder. You can see any bubbles and can see a color change when flushing brake lines.

It's a little slower that some of the other techniques, but works just as well...

 

[jarhed1984]

Bubbles want to go up. Dump it all then pressure bleed the system from the wheel hub up to the reservoir. You may be surprised the difference it makes.

 

[Apogee]

Bubbles want to go up. Dump it all then pressure bleed the system from the wheel hub up to the reservoir. You may be surprised the difference it makes.

This is generically referred to as a "reverse bleed" process and you're right, it can work very well. While reverse bleeding has always been commonly used on other hydraulic systems like mountain bike brakes, Reverb seat posts, etc, in automotive circles the main advantage is with ABS systems that would otherwise require special tools or electronics to push fluid through the ABS hydraulic control unit. There are reverse bleeder kits, however most won't want to pay what they cost. In my experience, most EB's are about as simple as it gets when it comes to brakes and can be bleed effectively in a variety of ways, so I would just pick the one you're most comfortable and/or familiar with and go for it.