Disc Brakes

[Bobs69]

I upgraded my 69 to disc brakes quite some time ago.  Believe it or not only recently noticed that the fronts are not grabbing the hardest.  The rotors still have cross hatch marks on them. 

I want to feel the front brakes grab more.  I replaced the rear and wow.  Expensive. 

Disc brakes are off of a 85 or older new Yorker.  New master cylinder (upgraded).  New style proportioning valve.  New flex lines on today (front). 

I know they work, I've done brake burns in the past.  Just not good enough I think.  I'd rather wear out the front pads then the rear shoes and drums.

[Cooter]

Bob, are you sure the lines are hooked up properly?. Should be like 70% frt. I have seen folks hook up lines that should go to rwar to front.


Aside from this, did you make sure if running manual brakes, that you have the correct calipers?

[Bobs69]

I new I should have mentioned the rebuilt brake booster!

How can I tell if the lines are on in reverse?  It was a simple R & R job.  I'll post a picture soon.

[Mopar Nut]

Have you tried readjusting the proportioning valve?

[Bobs69]

Have you tried readjusting the proportioning valve?

How do I do that?

[Mopar Nut]

Have you tried readjusting the proportioning valve?

How do I do that?

Is your proportioning valve adjustable? If it's not that could be your problem. Disc brakes moves more fluid. Sounds like the rear is receiving more fluid. Do you have drum brakes on the rear?

[Bobs69]

Yes drum brakes on the rear.  The Proportioning valve off of a newer car as well.  Not a summit racing deal.  Is it possible it's adjustable?

[Mopar Nut]

Does it have a knob?

[Bobs69]

No

[Mopar Nut]

You might try a adjustable proportioning valve on your rear line only then.

[John_Kunkel]

Before making any changes to the system I would do some brake testing; find an isolated spot and make some hard stops from different speeds to see if the rears lock up first (allow the brakes to cool between tests). If the rears aren't locking first you don't need a prop valve.

[Bobs69]

I'm going to take the wheels off and make sure the drums are set right and that the adjuster is moving freely.  They are all new so should be.  

Then I'll take it out like you said John and try to lock them up.  Does it have to be done on pavement?

[Bobs69]

Ok I've driven in a few times.  The rear brakes are locking up first.  The fronts, not at all.

[resq302]

If you are having the rears lock up before the fronts, then you need a hold off valve.  Its a brass shaped lower case t thing that delays the rear brakes a split second to allow the front discs to engage first.

[Bobs69]

If you are having the rears lock up before the fronts, then you need a hold off valve.  Its a brass shaped lower case t thing that delays the rear brakes a split second to allow the front discs to engage first.

Thankyou!  Never heard of it.  Is this an OEM thing?  Or aftermarket.  Any chance you can give me some more info on this.  A picture would be nice. 

Where does it mount?

[Back N Black]

This is the one that you need.

http://www.inlinetube.com/Prop%20Valves/PR104b.htm

[Bobs69]

there is a valve very similar to that on the rear differential.  is that for something different?  like balancing the left and the right?

It's in the shape of a Y

[John_Kunkel]

This is the one that you need.

http://www.inlinetube.com/Prop%20Valves/PR104b.htm

Hold off valve, prop valve....same same.

[Musicman]

If you are having the rears lock up before the fronts, then you need a hold off valve.  Its a brass shaped lower case t thing that delays the rear brakes a split second to allow the front discs to engage first.

You have that backasswards... the metering hold off valve found in disc/drum systems ensures that the rear brake shoes make contact with the drums before the front disc's can actuate.

[Musicman]

Hold off valve, prop valve....same same.

No they are not the same thing, they are two completely different things.

[Bobs69]

Music Man I phoned the inline people and tried to describe my problem to them and they seem to agree that I need that valve.  do you agree that it will settle my problems? 

[Musicman]

Your first mistake was talking to the folks at InLine Tube... Clueless and therefore Dangerous 

There are a number of issues that could be causing your problem, the simplest of which would be solved by installing an Adjustable Proportioning Valve in the rear brake line. If you find braking inadequate after testing and making the proper adjustments, then it's time to look at the front side of the system. Before doing anything however, a few pic's of your existing setup would be a great help, at least we could tell if you have the right components installed, and that things are hooked up correctly.

[Musicman]

Just for the record...

This is the valve that InLine has listed as a Hold Off Valve for Mopar in the link above. It is actually a non-adjustable proportioning valve... and their description of the valves function is completely hosed!
The folks at InLine don't even know what it is that they are selling to people, and that makes them dangerous IMHO.

[Musicman]

This is an example of an early Mopar Metering Valve (often referred to as a Hold Off valve). You can tell it's a metering valve by the little tit that sticks out the front. This tit is there so can manually override the valve when your installing new brake pads. Pulling on the tit, opens the valve, allowing brake fluid to freely flow back to the master at a much faster rate when your compressing the caliper piston. If you don't use this feature, compressing the piston will be slower and harder because you are trying to push fluid through a much smaller orifice within the valve.

[Musicman]

This is a typical old Mopar Combination Valve (Metering Valve, Hydraulic Safety Switch, Proportioning Valve, all in one unit). These were common in Disc/Drum systems.

[Bobs69]

Hmmm.  So you say the EASIEST way to fix this is to install an adjustable proportioning valve. 

[resq302]

When I had the proportioning valve out for repair, I had a pig tail in place and when I hit the brakes, the rear lines locked up and started the back end of the charger sliding around on me.  When this valve is installed, it delays the rear brakes from engaging or reduces the pressure going to it which allows the front brakes to engage more than the rears to prevent the rear end from locking up first and sliding around on you.

I also second the fact that In Line is a bunch of tool bags as I sent them back the defective proportioning valve not once but twice!  First time they sent it back to me saying there was no problem.   The valve acted like a one way valve allowing pressure and fluid to go to the back brakes but not back up to the master cylinder when the brake pedal was off.  They claimed there was no problem with it.  When I got an original and installed it, I had no problem.  Seems other people have had major issues with their stuff too.

[Musicman]

Hmmm.  So you say the EASIEST way to fix this is to install an adjustable proportioning valve. 

No, that's not what I said. What I said was...

Before doing anything however, a few pic's of your existing setup would be a great help, at least we could tell if you have the right components installed, and that things are hooked up correctly.

An adjustable proportioning valve would be the solution to the simplest issue. The simplest issue would be that you have everything installed correctly, and that you have eliminated all other possibilities. This would normally be the case, but its always better to check things out before you start throwing money away.

My first question here would be... do you have a metering (hold off) valve installed for your front brake lines. If the metering valve is frozen (it happens occasionally) it will result in the same issue that you have described. The front brakes will hold for torque stands, but they will lag during normal braking. You can tell if the valve is frozen by grabbing that little tit with a pair of pliers and giving it a little pull. It should move roughly 1/16" or slightly less, but it should pull out at any rate. If it doesn't move, then the valve is frozen shut and you are supplying pressure and fluid to your front calipers through a very tiny orifice.

[John_Kunkel]

Hold off valve, prop valve....same same.

No they are not the same thing, they are two completely different things.

Look at the pic in the Inline Tube link and then look at the same item in the FSM, Inline calls it a "hold off valve" and the factory calls the exact same thing a "proportioning valve"....same, same.

This is what happens when vendors and internet denizens use non-Mopar terminology; ditto for calling a "metering valve" a "hold off valve". "Hold off valve" is GM terminology, same as "Positraction"....doesn't belong in a Mopar forum.

[Bobs69]

Okay Musicman I got the pictures.  Been awhile since I've posted so lets see if this works.  

Now keep in mind, I got the car undercoated within the last few days.

[Bobs69]

Come on guys!  Help me out here.

[resq302]

First couple pictures is of the distribution block.  The last two pics are of the brass T that splits the front to rear line between the two rear wheel cylinders.