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Technical HOW TO SET ADJ. PROPOTIONING VALVE

Discussion in 'The Hokey Ass Message Board' started by rdynes01, Jun 20, 2014.

  1. rdynes01
    Joined: Nov 22, 2010
    Posts: 96

    rdynes01
    Member
    from colorado

    Just helped a friend put Chevelle discs on his 56 F-100.We know we needed a prop. valve to adjust line pressure between front discs and rear drums but what is a good starting point for setting the valve? All the way open? All the way closed? Half way open? Thanks for any input.
     
  2. F-6Garagerat
    Joined: Apr 12, 2008
    Posts: 2,652

    F-6Garagerat
    Member

    I put one in my last hot rod pickup, rear end was real light. It was 40 drums at all 4 corners with a dual master cylinder so same principal really. I started at the half way point. Found a big empty parking lot and kept adjusting it until I got to almost lockup in a panic type stop, then backed it off until I was happy with it. Maybe not the proper way to do it but it kept the back tires from locking up and throwing me into a spin when idiots jumped out in front of me. That's the goal.
     
  3. gearheadbill
    Joined: Oct 11, 2002
    Posts: 1,305

    gearheadbill
    Member

    Chances are unless you have a set of big 'n littles your proportioning valve won't be necessary. I'd start with it open all the way (no effect) and see. All a proportioning valve does is reduce the effectiveness of the rear brakes. With a much larger rear tire than front, one of these valves MAY be necessary because the larger rear tires act like a big lever. The larger the lever, the more effectively it works. Reducing the 'lever-effect' allows the front brakes to begin to stop the car first.

    Don't know if this is helpful but I've found them to be underneeded and oversold.
     
    Tman likes this.
  4. 65COMET
    Joined: Apr 10, 2007
    Posts: 3,086

    65COMET
    Member

    I run disc front,drums rear,dual master cylinder with an adjustable prop valve,big rear tires,small fronts.I adjust mine to send less to the rear brakes,it works great,been on the car for over 20 years!! ROY.
     
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  5. missysdad1
    Joined: Dec 9, 2008
    Posts: 2,945

    missysdad1
    ALLIANCE MEMBER

    F-6Garagerat has it right! A proportioning valve is required to reduce the effectiveness of the rear brakes - especially in a vehicle with a light rear end - during a panic stop when the vehicle's weight shifts to the front wheels in a rather dramatic fashion. Anybody who's tried to panic stop a pickup on wet pavement knows what happens when the rear wheels lock up before the front ones. Spin city - in a heartbeat! Don't let anybody talk you out of installing and adjusting a proportioning valve. Your life - and that of your family - depends on it.
     
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  6. F-6Garagerat
    Joined: Apr 12, 2008
    Posts: 2,652

    F-6Garagerat
    Member

    Thanks. With people on their phones and what not, more than a few folks scared the crap out of me. Truck stopped pretty damn good.
     
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  7. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,671

    gimpyshotrods
    ALLIANCE MEMBER

    Never trust anyone who makes blanket statements.

    Some cars need them, some don't.
     
  8. aircoup
    Joined: Aug 13, 2009
    Posts: 898

    aircoup

    how does this adjustment affect bleeding the brakes ive had trouble in the past and was told i needed a residual in line valve
     
  9. HemiRambler
    Joined: Aug 26, 2005
    Posts: 4,199

    HemiRambler
    Member

    Why do we need proportioning valves? Because the IDEAL braking bias (front pressure versus rear pressure requirements) are different and if that was the complete story the factory would just build a different "sized" brake for the front versus the rear - done! But wait! The factory doesn't do that - do they? Why? Because that is NOT the problem that they are trying to solve!

    The issue is this: The ideal braking bias is NOT one value for ALL CONDITIONS. Meaning it's not as simple as designing an ideal system with a 70/30 split and calling it good everywhere. What is "everywhere" - Everywhere is RAIN, ICE, BLACKTOP, CONCRETE, GRAVEL ETC. All the road conditions that affect our traction.
    So as we all know if you put more weight on a tire it will have better traction...same reason you want to transfer weight to your rear tires when drag racing - more traction!

    The GRAVEL ROAD - so when we are panic stopping on a gravel road we have 2 main things working against us - first off traction is reduced ACROSS the board. What this means to your braking system is that you will LOCK UP the brakes at a VERY LOW system pressure (let's call it 500PSI). Also your weight shift (weight transfer) to the front will be VERY LOW. So in this case lets call it 55/45. Meaning the fronts can do 55% of your braking. (Yes these are made up numbers for the sake of comparison/conversation).

    The WET ROAD - so when we are panic stopping on a wet road we still have 2 main things working against us - first off traction is reduced ACROSS the board, but maybe not as much as the gravel road. What this means to your braking system is that you will LOCK UP the brakes at a LOW system pressure (let's call it 700PSI). Also your weight shift (weight transfer) to the front will be LOW. So in this case lets call it 65/35. Meaning the fronts can do 65% of your braking.

    The IDEAL ROAD - so when we are panic stopping on an ideal road we have nothing working against us - other than weight transfer. What this means to your braking system is that you will LOCK UP the brakes at a MUCH higher system pressure (let's call it 1000PSI). Also your weight shift (weight transfer) to the front will be VERY HIGH. So in this case lets call it 75/25. Meaning the fronts can do 75% of your braking.

    So with this varied set of conditions the proportioning valve is not simply a fixed value device - meaning it doesn't always put a certain percentage out - it varies. Now granted if you look up the pressure curve it isn't in a constant state of change (although ideally that would be better). Your brake pressure requirements (for an ideal system) would have the brake pressure ratio vary based on all conditions, but some really smart dude figured out one way to do this would be to put in a "pressure" regulator that would allow the brake system pressure to more closely follow the ideal pressure curve. Pure genius when you really think about it.

    Food for thought: Look at some of the old pickup truck brake systems - they installed a variable proportioning valve that adjusted braking bias based on the HEIGHT of the truck. Reason: a truck FULL of rocks has a much different brake requirements than a truck with an empty bed! My guess is that they do that with computers now. But it is interesting that the factory did put those in there.
     
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  10. aircoup
    Joined: Aug 13, 2009
    Posts: 898

    aircoup

    well this didnt answer my question,,informative but not what Iwas lookin for,
     
  11. HemiRambler
    Joined: Aug 26, 2005
    Posts: 4,199

    HemiRambler
    Member

    Never said it answered your question, but I'll play....

    It doesn't. There ya go.
     
  12. V8 Bob
    Joined: Feb 6, 2007
    Posts: 2,658

    V8 Bob
    ALLIANCE MEMBER

    When bleeding through an adjustable or load-sensing (variable) proportioning valve, it's best to cycle the valve through it's full range at least twice.
    Residual valves (stock or aftermarket 10 lb.) are needed with older pre-mid '70s drum brakes, but can also help pedal feel with later drum brakes. The 2 lb. inline valves should only be used with disc brakes when the master cylinder in below floor mounted.
     
  13. aircoup
    Joined: Aug 13, 2009
    Posts: 898

    aircoup

    thank you v8 bob,, hemi rambler well?
     
  14. Ole don
    Joined: Dec 16, 2005
    Posts: 2,915

    Ole don
    Member

    If you have a blacktop or concrete driveway, water it down and test brake lockup with trusty wife watching from the side to tell which end locks up first. More water, more adjustments. Most big rear tires are like a huge flywheel back there.
     
  15. HemiRambler
    Joined: Aug 26, 2005
    Posts: 4,199

    HemiRambler
    Member

    aircoup, your question isn't very clear, but I took it to be what I highlighted above, to which I answer, "it doesn't". I've never had to adjust my bleeding procedure to account for proportioning valves. Start at the furthest back - finish at the nearest front. Residual pressure valves are needed for drums regardless and discs when M/C are mounted low, they don't enter the equation for proportioning valves, but may in some cases make bleeding easier (I don't know I never compared with and without for ease of bleeding), but in any case that's NOT their purpose - they are about controlling excess pedal travel and possibly sucking air in past a seal.
     
  16. First, you have to seat (burn-in) in the new brakes. Let them cool down. Check your air pressure!!!!
    Find a clean dry area, parking lots are good.(most roads have a crown), with the proportioning valve wide open do a panic stop where you lock up the tires. If the fronts lock up first you need to reduce their effort with the valve in the front line, if the rears lock up first (most do) crank on the proportioning valve until all four wheels lock up together. Now try it on a wet parking lot.
     
  17. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,671

    gimpyshotrods
    ALLIANCE MEMBER

    Leave it wide open while bleeding.

    If your master cylinder does not have built in residual valves (commonly old, all drum ones) you should install them when:

    On all circuits, 2lb for disc, 10lb for drum, if your master cylinder is below the calipers/wheel cylinders

    Otherwise, on drum circuts, 10lb, in all cases. They keep the seals preloaded, to prevent air being sucked back in.
     
    Last edited: Jun 21, 2014
  18. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,671

    gimpyshotrods
    ALLIANCE MEMBER

    This thread is talking about two separate, very unequal things.

    This is a combination valve:
    [​IMG]
    [​IMG]
    It provided the dynamic front-to-rear brake biasing adjustment that HemiRambler expertly described above.

    It is NOT and adjustable proportioning valve.

    Those are these:
    [​IMG]
    or
    [​IMG]
    or
    [​IMG]
    All these are capable of doing is reducing the pressure/flow of fluid to the rear brakes. They have no active, dynamic function, and respond to nothing, except the turn of the knob. There are no moving parts in these, except for the knob and shaft.

    Once you set one, they are identical to have a static setup, with no adjustable valve.
     
    Last edited: Jun 22, 2014
  19. seb fontana
    Joined: Sep 1, 2005
    Posts: 6,610

    seb fontana
    Member
    from ct

    ""
    All these are capable of doing is reducing the flow of fluid to the rear brakes. They have no active, dynamic function, and respond to nothing, except the turn of the knob. There are no moving parts in these, except for the knob and shaft.

    Once you set one, they are identical to have a static setup, with no adjustable valve.
    gimpyshotrods, Today at 12:15 PM ""


    No, do not agree with the above statement. But since I don't have one to cut apart I can't see/tell how it is built. If it is just a valve it can only limit pressure by limiting flow rate, not much flow at all in a brake system and once flow stops [very quickly in a brake system when all the shoe/pad clearance is taken up] the pressure would become equal on either side of valve. If it did not proportion it would just be called an adjustable valve? I think HemiRambler explained it pretty well
     

    Attached Files:

  20. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,671

    gimpyshotrods
    ALLIANCE MEMBER

    I am not sure that you understand. The black valves shown above have no ability to interact with the front brake circuit. There is no front-to-rear proportioning happening here. There is no dynamic bias alteration during operation.

    None, zero, zip, nada. They are simply not attached to it, in any way.

    All they do is reduce the chance of the rear brakes locking up first.

    I will see if I can find a spare in my bins, and take it apart to show you.

    What HemiRambler described is exactly correct, for the brass combination valve that I pictured above.

    That is not adjustable, at-least, not easily.
     
    Last edited: Jun 22, 2014
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  21. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,671

    gimpyshotrods
    ALLIANCE MEMBER

  22. HemiRambler
    Joined: Aug 26, 2005
    Posts: 4,199

    HemiRambler
    Member

    Gimpy, I am not sure we are entirely on the same page or not. Proportioning valves - the brass ones, the Direct Connection ones even the black Speedway one I have all work similar to the manner I described above. Humor me a bit - I know you know this but let me go thru it:
    [​IMG]
    The ideal curve is what we'd get in a perfect world and would put our rear brake pressure at a point just below lockup at all pressure points with regard to the fronts. But let's step back just for a minute to make sure we are all on the same page.
    In the graph above - IF we put the same exact brakes on the front and rear and ran them at the same pressure - the relationship would be a line at a 45 deg angle (100PSI front/rear, 200PSI front/rear, 300PSI front/rear - etc. But! we all know that would suck since the front brakes do more work than the rears. So the factory could just make the rears LESS effective than the fronts and call it a day, but they do not for a multitude of reasons - one being WEIGHT TRANSFER of the vehicle. It is that weight transfer which is the problem we are trying to address with the proportioning valve. That changing ratio of IDEAL pressure from front to rear is what our goal is - that is what will keep our brakes happy whether we are in gravel, wet, or dry road conditions. So what the geniuses have figured out - represented by that IDEAL curve above basically says you can label those conditions as "operating pressure zones" on our curve above - starting left to right - crappy conditions (gravel), so-so conditions (rain), ideal conditions (dry). Each one operates at a respectively higher/lower pressure and therefore a different ideal ratio.
    So is there a dynamic aspect to the operation of the brakes WITHOUT a valve - of course not the line is STRAIGHT in our graph. Is there a dynamic aspect to the operation WITH a proportioning valve - well sure - there is a point when we change the pressure ratio - (IIRC they call that the Changeover Pressure) - I agree it's not a constantly changing relationship - so in that sense it's not dynamic, but it does CHANGE - it's trying to "bend" our pressure relationship to mimick the actual curved ideal one (we're crude by comparison since it's just two straight lines, but it does get rather close to that prefect (ideal) relationship we are striving for.
    So I am saying YES all proportioning valves - IF they are actually a real proportioning valve work in this way - each one I have purchased all show the changeover pressure point and where it adjusts. All have come with instructions similar to this:
    [​IMG]
    So twisting the knob - results in raising/lowering that change over point - once adjusted it acts the same as the one in the first graph.

    So I say Yes there is some dynamic aspect - but not in the sense that it is always changing. In chart 2 , Once set at position 1 it will always follow that makeshift "curve" - that makeshift curve represents a dynamic relationship between front and rear - meaning ONE ratio is NOT ideal for all braking (traction) conditions.

    The genius that came up with the simple proportioning valve has come up with a very simple way to try and mimick the ideal curve with a simple concept.

    This concept is very similar to a drag race fuel system with a high speed lean out. Your ideal fuel curve is not a straight line either (efficiency drops) so one way to "tweak" your fuel is to add leanouts - which do exactly the same thing - they lower pressure (rate of change) again trying to "bend" the pumps output curve to match the ideal curve that the motor wants. Always pump too much and reduce more and more to achieve what you want. You want a "smoother" curve - add more leanouts.
     
    Last edited: Jun 22, 2014
  23. aircoup
    Joined: Aug 13, 2009
    Posts: 898

    aircoup

    ok hemi rambler , thats alot more detailed than i thought it would be i feel like ive opened a can of worms here , thank you fr all your information EVERYBODY,
     
  24. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,671

    gimpyshotrods
    ALLIANCE MEMBER

    I looked for the one I had kicking around the back of the shop, that has damaged threads. I did not see it, but I couldn't look long. Sunday's I'm on wife-support.
     
  25. 360FE68
    Joined: Oct 12, 2020
    Posts: 2

    360FE68

    First I will answer the question at hand. This is the method the aftermarket adjustable valve manufactures provide. It is important to not that it is in reality a best guess type adjustment. For a true adjustment would require a lot of calculations, and test equipment most gearheads are not willing to go through.

    To adjust an after market prop valve will take several attempts.

    1.) Open the valve all the way. AKA no brake biais.

    2.) Drive at about 30 mph and stop hard. Taking notice if the rears are locking up first.

    3.) Turn the valve in which ever direction closes your brand/model valve if the rears are locking up first. About 2 turns at a time.

    4.) Repeat steps #2 & #3 until your fronts brakes lockup just momentairly prior to your rears. This will make sure your rearend will not wash out during a panic stop on a dry road.

    5.) Repeat step #2 at 50mph to verrify the desired function at highway speeds. Repeat step #3 as needed.

    6.) If you plan on doing a lot of hualing in a truck, you will want a slightly different result to attemot to gain some safty when loaded. The better option is to use a stock combo valvs.

    Basicly you will lock your rears up slightly prior to your fronts. This way you rears will be more effective when loaded. This is why aftermarket adjustable valves suck for trucks that will still be used as trucks, and cars that are driven on a regular basis. See why bellow for a detailed reason.

    Yes, as someone else already pointed out. Aftermarket adjustable prop valves are not dynamic. They are intended for track use, and street rods that spend more time in the garage, or on the trailer then they do on the road.

    All they do is reduce the preasure to the rear by a given percentage each and every time you the hit the brakes. They do this by the same amount regardless of the changing conditions, unloading of the rear, low traction, etc.

    A stock combo valve, amongst other things, will reduce the rear line preasure in a dynamic fasion via a bypass passage and spring loaded valve. As the rear line preasure spikes in the bypass passage it acts upon the spring loaded valve temporaily reducing the rear line preasure for a brief predetermined amount of time. This gives the front brakes time to do what they need to. Then the rear line preasure is equalized with the static line preasure generate by your foot.

    During normal braking when you are not at risk of locking up your brakes, a stock combo valve provides near equal line preasure front and rear to provide the best braking performance. An aftermarket adjustable valve does not. It continues to drop the rear presure by the preset percentage. This is a major draw back for regular driving.

    As you can see there is a lot more going on with the stock dynamic valve vs. the static adjustable valves. There is a reason circle track guys install them ware the driver can adjust them while they are driving for the given track conditions. They do not adjust themselves. Full stop!

    In a regular street car/truck this is dangerous to install. An appropriate stock style combo valve for your setup is not only far superior, but a much safer option to install.

    Have no doubt that if you are in an accident, and your or the other guys insurance company finds out an aftermarket adjustable valve is installed, they will do thier best to point towards your unsafe setup as the cause of the accident. In part, or in full. If an car accident injury lawyer is involved, things get much worse for you.

    Nothing is worse then injuring others due to your not understanding of the custom subsystem you modified or installed. Then being held financial liable for all cost incurred, and possible criminal neglagence as well ranks close. Ultimately, knowing my choices injurred or killed someone else would still be worse.

    I'm in the process of converting my 1968 F100 4 drum truck to front disk brakes using stock off the shelf parts. For both the ease of obtaining maintianence parts, and reproducing a safe braking system. I have put a lot of research into wether or not to use an aftermarket adjustable valve. Since I believe in driving my truck everyday, and using it as a truck. I will be going with a stock late '70's combo valve.

    This combo valve is the correct valve for my truck's wieght loaded and unloaded. Thanks to all the engineering work the Ford engieneers have already put into ensuring a safe setup. This is one area of design that was not skimped on. Take heed in that, if they did not skimp on it, niether should you.

    A simple and safe sollution to determining which stock style combo valve you should use is, to give the guys at InLine Tube (or similar reputable company) a call. Accurately describe your application, and brake setup. They can tell which stock combo valve is best for your application & brake setup. It's the safest, and least legaly risky option.

    If not for your own safty, then for the safty of others on the road!

    Even Willawood's "combo valve" is not a true combo valve. It is thier adjustable static style valve with ports designed to provide a cleaner looking plumbing install. It does not provide the dynamic valving of a stock combo valve. There are times when stock is better then aftermarket, and this is one of them.

    TLDR;

    Some performance race parts are best left strictly for the track. An aftermarket adjustable prop valve is one of them. Be safe for your self and others, physicaly & legaly! Do the research to find the best stock combo valve for your setup.

    If by chance this will be a track vehicale. Then by all means an aftermarket adjustable static valve may be your best option.
     
    gnichols likes this.
  26. goldmountain
    Joined: Jun 12, 2016
    Posts: 2,231

    goldmountain

    A lot of smart guys on here. Not one of them, myself. However, since I mounted my master cylinder behind the dash with a 90 degree bellcrank, and with the brake lines already inside the car, I mounted the adjustable prop valve under the dash. I can adjust it as I go down the road.
     
  27. gnichols
    Joined: Mar 6, 2008
    Posts: 10,798

    gnichols
    Member
    from Tampa, FL

    I would never have the rears lock up before the fronts, regardless of intent / proposed uses. There is a good chance you'll spin out in a panic stop if not a very experience driver. A friend did that a few years ago in his hot rod Chevy coupe in Atlanta. He used all 4 lanes and the guard rail to stop. He told me later he always set his brakes for a rear bias. Your fronts do far more braking than the rears. But I like the rest of your test program. Many moons ago I took a Keith Code motorcycle training / racing class. Took me several years to rid myself of the habit of using the rear brakes on my bikes until down to very slow speeds, or intentionally breaking the rears loose like on a dirt bike. I think he reported 85 percent of the braking was done on the front wheel. Cars are similar.
     
  28. 360FE68
    Joined: Oct 12, 2020
    Posts: 2

    360FE68

    Lockup was a bad choice of words. Engage would have been the better word to use.

    Through many conversations with the different aftermarket brake manufactures, it's the only way to ensure a 1/2 ton or bigger truck can stop safely when load near or at capacity with an adjustable valve installed.

    When loaded the rear breaks lose a great deal of effectiveness trying to stop the added wieght. Stock combo valves make adjustments for this, and decrease the delay to full line preasure to the rear brakes.

    While your fronts do a great deal of braking, your rears are absolutely esentialy when loaded. Your fronts will over heat and fade quickly without proper rear breaking when loaded.

    A static adjustable valve has no means of doing this, and it is the middle ground between having your rears lockup first, and not having enough stoping power when loaded. It's all part of the draw back of using a static adjustable valve on a truck, or daily driver.

    It's one of those parts that seems cool, and better then thier stock counterparts. Right up until you learn you are losing a great deal of safty.
     
    gnichols likes this.
  29. 1971BB427
    Joined: Mar 6, 2010
    Posts: 5,886

    1971BB427
    Member
    from Oregon

    I was told many years ago that an adjustable proportioning valve has a certain amount of restriction even when all the way open. So installing one will have some percentage of proportioning, even before you begin to adjust it down.
    I always install them on a disc drum system, and often I've found there's no need to adjust them, so maybe they were right, or maybe I didn't need one anyway?
     

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