Proportioning valve..where's it go???

ok this might sound stupid but....been alot going on lately...so where does an adjustable proportioning valve go in the brake system?? In relationship to the residual valves ect...
Summit said it wouldn't be delivered till Monday or Tuesday..but out came today and ol Bob is supposed to be by today to run the front lines...been told the residual valves go about a foot after the master cylinder???sorry for all the questions but I'm run
ning out of time till Cobo

 

Check this out....

http://www.piratejack.net/index.php...onfigurations&catid=12:tech-support&Itemid=18

 

1. First you have to determine IF your system needs a porportioning valve.
This is easy....drive the car, hit the brakes and see which brakes lock up first.
The porportioning valve goes in that line to restrict it so it locks up the same
time as the other axle....If it is your avatar, it will probably be the front.
2. Does your master cylinder already have a residual valve? most do.
3. disk-drum, drum-drum, 4 disk, makes a difference.

 

yes its my avatar...38 steel topolino...325 Hemi with a world cl*** gm T~5...running metric gm disc up front..58~60 olds housing in rear with 2 rear shoes..master is a vette... 60 s...disc drum unit..but I'm leaning towards an aftermarket unit...

I've already have a new adjustable proportioning valve and the two and ten lb valves...just want to ensure i get it right the first time

 

yes its my avatar...38 steel topolino...325 Hemi with a world cl*** gm T~5...running metric gm disc up front..58~60 olds housing in rear with 2 x ll rear shoes..master is a vette... 60 s...disc drum unit..but I'm leaning towards an aftermarket unit...

I've already have a new adjustable proportioning valve and the two and ten lb valves...just want to ensure i get it right the first time

 

In the rear line, between the master cylinder and the 10lb. residual valve. I have built over 100 cars (that's my job), and have yet to find one that did not benefit from a proportioning valve. You can run without one, and your brakes might work fine. That does not mean that they are working as good as they could. Tuning is everything.

If you are running a brake light pressure switch, put that in the rear line, between the master cylinder and proportioning valve.

As for component position, location in sequence is critical, distance between components in a hydraulic system is irrelevant.

 

Great info Hussey, THANKS

 

I'm running mine way back near the rear axle, and it's worked great for years now. I put it there because it was easy to install, and not out in the engine bay where someone could reach down and tweak it easily.

 

mine is mounted to the crossmember right above the rear axle, right next to the soft line going to the axle itself... a good brake system needs a prop valve. they are cheap, they are simple to adjust and make your brakes work more effectively

 

Lets get this straight, this is not a proportioning valve, its a fluid limiting valve, sort of like a water spigot.
Will it work, well yes if you have to meter the flow of fluid because you need to balance the brake bias on an odd ball wheel cylinder combination but its a band aid to mask a screw up. .
Remember all you are doing is limiting the flow of fluid to the installed brake circuit cylinders. Its more of a race car part for braking weight transfer.
Do you need it, NO, not really if you have matched the piston diameter of the master cylinder to the specs similar to the size of the master cylinder of the brake wheel cylinders used.
My answer to the question where does it go, back in the mail to the vendor as an unused return part.

 

After never seeing any benefit after testing with and with out I have ditched using them also and was going to say toss it BUT looking at his Avatar pic I would be inclined to intsall it just to see.

 

Let's see...car weighes less then 1900lbs in stock trim..rip of 4 fenders...a set of running boards...gut the flooring...and all the metal around the firewall and inner fender supports...pull the 3 cylinder cast iron motor..cast iron Trans...add a 325 Hemi up front...aluminum wc t~5 Trans..urea i think its a tad noise heavy...even though the rear of the Hemi is back even with the door posts..


Seriously, I'm just trying to get this thing to stop..on a dime..gonna be a daily driver, not a race car..and i think it'll be really fairly well balanced..all things considered..i got a ton of set back on the motor...gas and battery in rear..and my 173 lb ***...
Thanks for everyone s view and ideas...
Sent from my DROID device using the TJJ mobile app

 

If you are runing a disc/drum brake setup you should have a proportioning valve to prevent rear wheel lock up. Drum brakes only need 1/2 the line pressure as discs do. Without one the rears would lockup before the fronts in a panic stop. A proportioning valve is used to limit presuure to the rear brakes.

 

He's going to need all the pressure/braking he can get to the rear with those big diameter rear tires............. JMO

 

you tell 'em ****... we haven't used p. valves for years on personal or customer hot rods. Main reason is that 95% of hot rods have big & little tire/wheel combos & most times front discs. Even with 4w drums (like on my 3w), the larger tire in back has more footprint, braking action/etc. We did a test for one of the car mags in 90's which proved it. But, if U gotta have it, put in the rear. p/s, put the brake lite switch as close to the master cyl. as poss. so gets the pressure more immediately. A more sensitve one is even better. jat

 

Disc/drum set up? Use adj. prop valve as close MC as possible. Most have a spot for a stop light switch or it is already there. Drive it and adjust as ness.

 

If so then why does the front disc take a 2 lb residual valve and the rear shoes take a 10 lb residual valve??
Not Tryin to be a ***...just don't understand if this is true........besidesif it is, i need to swap them as we just finished installing the lines, adjuster valve, and residual valves this afternoon....



Sent from my DROID device using the TJJ mobile app

 

Each residual valve is designed to keep the shoes or pads close to the surface they are applied to. The farther away they are, the longer it would take your brakes to come on. A few milliseconds of delay could mean an accident.

Disc caliper pistons retract slightly when pressure is released. They have no return mechanism to overcome, hence 2psi. Drum brakes have return springs, a mechanical, positive return mechanism, which must be partially overcome, hence 10psi.

 

<TABLE cellSpacing=0 cellPadding=0 width=619 border=0><TBODY><TR vAlign=top><TD width=11></TD><TD width=595>What does a proportioning valve do?
A proportioning valve is used in the rear to decrease the rate of pressure rise to the drums relative to the pedal force as weight is shifted to the front during braking. This prevents the rear from locking up under hard braking conditions.
What are the symptoms of a bad proportioning valve?
If your prop valve has gone bad your rear wheels will lock up easily, especially on wet surfaces.

What does a metering valve do?
A metering valve or "hold off valve" is used in the disc portion of a disc/drum system to hold off the application of the front discs slightly allowing the slower reacting rears to catch up. This provides rear stability on wet surfaces and reduces excessive pad wear.
What are the symptoms of a bad metering valve?
Your car will nose dive and the front pads will wear too fast.

What does a residual valve do?
There are two different uses for residual valves. The 10 lb valve is used to hold a residual pressure to the drum brakes to keep the shoes out close to the drums giving a higher firmer pedal. The 2 lb valve is used in the disc when the master cylinder is lower than the calipers to prevent back siphoning of the fluid from the master.

What are the symptoms of a bad residual valve?
The brakes will be very spongy and you will need to pump the pedal to get good brakes.

What is a combination valve?
A combination valve incorporates metering and proportioning into one valve providing all necessary valving for disc/drum systems.
See below
Should I use an adjustable proportioning valve?
Not if you can help it. The adjustable valve will only provide the proportioning function and not the metering that is needed.
Descriptions

METERING
The metering or hold off valve is used in the brake system to better balance the front to rear brakes. The valve does not allow the pressure to rise at the front disc brakes until the pressure at the rear drums has risen sufficiently to overcome the brake shoe springs. At this point the valve opens to allow full pressure to build at the front brakes.

PROPORTIONING
The proportioning valve modulates the pressure to the rear brakes. The modulation is necessary to minimize rear wheel lock up found in heavy braking and to compensate for the differences in braking conditions in front disc / rear drum systems. As pressure is applied to the system full pressure is allowed to the rear drums up to a certain point. Beyond that point the pressure to the rear is reduced preventing rear brake lock up.

RESIDUAL
There are two different residual valves. A ten pound residual valve will maintain a line pressure to the rear to keep the drum brake shoes out close to the drums giving a higher firmer pedal. Without a ten pound residual pressure to the rear you will experience a spongy pedal. A two pound residual valve is required whenever the master cylinder is lower than the calipers to prevent backflow of fluid from the calipers to the master.

COMBINATION
A combination valve incorporates metering and proportioning into one valve. These are available for disc/drum or disc/disc systems.

ADJUSTABLE PROP VALVE
The adjustable proportioning valve is used when you have a special rear condition that requires higher or lower pressure than a normal condition. You should always use a metering valve to the front when using the adjustable.

http://www.mpbrakes.com/technical-support/reference-valves.cfm

http://www.mpbrakes.com/technical-support/reference.cfm




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I hear what you are saying regarding big and little tire sizes and having more grip in the rear. What about on wet pavement? I am thinking that a larger footprint on wet pavement would be more prone to hydroplane. I know most rods never go out in the rain, but sometimes you have no choice. I would still plumb it. He's already got it. Test stopping distances on both wet and dry pavement, and see what happens. If it's not needed, you could run it wide open. I'd like to know for my own benefit. I do have an adjustable proportioning valve on my 26 but you guys have built alot more cars than I ever will.

 

BobMcD, Close your adjuster all the way, take your car out on a dirt road, at 30 or so and hit the brakes. Watch what happens to your tires braking.
Now do same with adjuster at 1/2 way.
Again at full open. My bet is you will not see a substanial diff. in any setting. Would like to hear results.................

 

Thanks Dane. Great information!.

 

Drum brakes use more residual because they have springs pulling the brake shoes back where disks don't.

 

I get the topo going I'll do some tests...this really has turned into a very educational thread for me....be interesting to try the different scenarios ......would have been a great thread for tech week

 

"gets the pressure more immediately"???? WTF, it's hydraulic. There's no "more immediately".
Whenever the brake pedal is pushed any/all pressure generated by the M/C will be realized thru the entire system at the same time, in a proper air free system

 

Fundamental truth.

 

The simple answer is to install the residuals as close to the master as possible, and locate the prop valve anywhere downstream before the rear brake tee.


gimpyshotrods
<table border="0" cellpadding="6" cellspacing="0" width="100%"><tbody><tr><td cl***="alt2" style="border:1px inset"> </td></tr></tbody></table>Each residual valve is designed to keep the shoes or pads close to the surface they are applied to. The farther away they are, the longer it would take your brakes to come on. A few milliseconds of delay could mean an accident.


Disc caliper pistons retract slightly when pressure is released. They have no return mechanism to overcome, hence 2psi. Drum brakes have return springs, a mechanical, positive return mechanism, which must be partially overcome, hence 10psi.



Simply not true. Drum brake residuals do not-cannot overcome the shoe return spring force, to allow the shoes "close to the surface", and they weren't designed to. They prevent air from entering past the wheel cylinder cups, period. No way a 10 lb residual can overcome a 75-100 lb shoe return spring.
The 2 lb disc residual is strictly aftermarket, as production disc brakes never had or needed residuals, because master cylinders were all firewall-mounted in the '50s, years before disc brakes. All they do is keep fluid from siphoning back into the master when it's mounted below the calipers.
I know some of the brake suppliers state what you posted in their so called "tech" sections, but sadly they're totally wrong. Too bad many companies don't have a clue about some of the brake products they sell.

 

That's what I was going to say and it's also what I did on my "A" sedan and it hasn't given me any trouble and works great. When I built the car 12-13 years ago I didn't know what I was doing so I just followed the advice given by the good men at Speedway Motors. Car now runs mid 11's at the HAMB drags and haven't had any trouble stopping from 115 mph and I am braking pretty hard at the end.

 

OK, we get wild ***ed theories on here about all sorts of things; but DAMN guys, this is BRAKES. You know, those things that are on the car to SAVE YOUR LIFE in the event of an emergency... READ A BOOK!

The residual valve is NOT there to keep the pads/shoes close to the friction surface. It is there to prevent the backrush of fluid from causing a siphon effect and evacuating the wheel cylinder or caliper. DON'T EVEN tell me this is not possible...that's why they were invented. Residual valves are most necessary in systems where the master cylinder is mounted below the caliper or wheel cylinder (down hill back flow). They should be mounted as close to the M/C as possible, ahead of any other inline device (prop valve, etc).

Regarding the prop valve: **** Spadaro is spot on in theory. The reality is, sometimes we use parts that don't match perfectly (hot-rodding, right?)... The prop valve is designed to keep the rear tires from locking up before the fronts and causing the car to spin under heavy braking. It is marked with "increase" and "decrease" relative to the pressure applied to the rear brakes. Count how many turns the valve will move between full open and full closed (softly seated).

Set it by starting out full open. Drive the car about 25 mph and POUND the brakes. If the rears lock first, close the valve 1/2 way and repeat the test from exactly the same speed. If the fronts lock first, open the valve back up 1/4 of the total turns and try again. If the rears still lock first, close another 1/4 of the way and try again. This just eliminates having to sneak up on the correct setting from way off the mark. If you keep splitting the fraction of total turns you will hit the mark (fronts JUST lock first) fairly quickly. Relative tire size has NOTHING to do with whether or not a system needs a prop valve. Without it, you have NO way of properly adjusting brake balance. You may "get lucky" and have the system work fine with it full open. Great. Leave it there in case you or a future driver decide to change tire sizes, brake type, etc...

 

Started a thread on master cylinders..looking for info on brake and clutch matter cylinders..lots of great info here..thought maybe a few of you guys might jump over there and add to it