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Technical converted to 4 wheel disc, manual, do we need brake residual valves?

Discussion in 'Traditional Customs' started by 55Thunderboy, Jun 5, 2017.

  1. 55Thunderboy
    Joined: Mar 27, 2009
    Posts: 356

    55Thunderboy
    Member
    from NYC

    Hi guys i just helped my buddy convert over his 62 Chevy Bubbletop over to 4 wheel disc brakes.

    the car originally had 4 wheel drums and stopped fairy good.

    We installed a Wilwood Dynalite kit with a 15/16 tandem manual master cylinder. We installed a new Classic tube stainless hardline kit for the dual circuit as well. Wilwood combination prop valve as well was installed.

    the car stops OK, not as impressive as we expected and not as aggressive as the drums we removed. We pressure bled the system 3 times using the Motive Power bleeder and my Phoenix bleeder, def no air. the pedal seems to have a bit more travel before it engages as compared to the 4 wheel drums we removed. pedal also feels a tad spongy but it might be from the master cylinder bore and caliper pistons

    When we went out back and opened the lines after a few test drives fluid does pour out evenly, when we go up front and pull one of the front wheels and remove the braided brake hose at the caliper fluid does not pour out at the same rate, almost get 1 drip and thats it, seems like something is weird.

    this had us thinking last night if maybe we should install 2lb residual valves on the front circuit or not?

    I have never used a residual valve on any car and was always under the impression this was for guys with drum brakes or masters mounted under the floor on hot rods.

    any suggestions here guys? Why would this lack or pressure occur only on the front circuit with a firewall mounted master? would we need 2 residual valves up front?
     
  2. fiftyv8
    Joined: Mar 11, 2007
    Posts: 4,892

    fiftyv8
    Member
    from CO & WA

    Is there a power booster being used in this setup???
     
  3. 55Thunderboy
    Joined: Mar 27, 2009
    Posts: 356

    55Thunderboy
    Member
    from NYC

    no power booster went from manual drums to manual 4wheel disc
     
  4. V8 Bob
    Joined: Feb 6, 2007
    Posts: 2,564

    V8 Bob
    ALLIANCE MEMBER

    Residuals are not needed or wanted with discs and a firewall or high mounted master cylinder.
    Disc brakes are not self energizing, requiring higher fluid pressure than drums, and is why most production 4-wheel disc systems use a booster. The other option with a manual system is higher pedal ratio, being careful to also allow full pedal travel.
    The 15/16" master may be too marginal for your large disc calipers.
    Make sure the pedal can fully return with it's own return spring, and +/- 1/16" push rod clearance.
     
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  5. racer_dave
    Joined: Nov 16, 2012
    Posts: 205

    racer_dave
    Member

    If the master cylinders are higher than the calipers you do not need residual valves. You said the MC is dual 15/16? what size are the pistons on the front & rear calipers? You may not be moving enough fluid. Also, you may need to adjust the front MC to a smaller bore to get more pressure to the front calipers to increase stopping force.

    But it will all start with the M/C bores and the caliper bores/volumes. Let us know what they are.

    PS- Another thing to look at is the pedal ratio. if that ratio isn't high enough, you're not getting enough force on the M/C.
     
  6. gimpyshotrods
    Joined: May 20, 2009
    Posts: 16,581

    gimpyshotrods
    Member

    x2 on this. A 15/16" master cylinder might be good for PSI, but displaced fluid volume may be the issue.

    For perspective, a generic GM vehicle, with a booster, might have a 1-1/8" master cylinder.

    Given the same stroke, that is a 20% increase in fluid displacement over a 15/16" master cylinder.

    It is a delicate balance between bore (master cylinder and caliper), stroke, pedal ratio, and pedal pressure. It is very easy to get wrong.
     
  7. oj
    Joined: Jul 27, 2008
    Posts: 6,225

    oj
    Member

    I went thru same thing from Wilwood, (complete system, 4 corner dynalites, MC, prop valve etcetc), I assumed I I measured the brake pedal ratio wrong and bought a different MC (started with 1" and went to 15/16ths) without improvement, got into serious fight with asshole rep and finally put a Strange 1" MC and it stops much better but not as good as it should.
    I've got a pair of those highdollar Wilwood MC's that I don't even dare to sell. Junk as far as I can tell.
     
    Just Gary likes this.
  8. 55Thunderboy
    Joined: Mar 27, 2009
    Posts: 356

    55Thunderboy
    Member
    from NYC

    My buddy also went through this kit with the wilwood rep for the past year picking ever part out they suggested as a "perfect" kit before he bought it now they are telling us we got the wrong pedal ratio etc, I don't buy it for smack man because the drums stopped the car much better. I called over to them today then the kid in the tech dept told me we should try new pads, I said wtf another $400 to test out new pads it should not be required for a street cruiser. Then he suggested to switch to a power booster I kinda lost it and hung up on the guy. I never was a fan of this stuff and I also thinks the quality isn't that great. He should have went with ssbc imho. My friend has serious buyers remorse and we spent all weekend on this conversion to be dissapointed in the end result, just sucks.
     
  9. Jimmy2car
    Joined: Nov 26, 2003
    Posts: 1,707

    Jimmy2car
    Member
    from No. Cal

    V8 Bob has the answer.
    I have never seen a 4 wheel disc system without
    a booster, but have seen a few with 2 wheel discs
    that were manual in operation.
     
  10. I've only driven a couple of cars with manual disc/drum brakes, but they made me really appreciate any basic self-energizing manual drum/drum brake system. To me, disc brake systems are good candidates for a booster.
     
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  11. Fordors
    Joined: Sep 22, 2016
    Posts: 2,471

    Fordors
    Member

    Well I have a different take on that. My
    '32 Fordor with '70 Chevelle calipers and a Maverick eight inch rear end along with a 1 1/8" GM master stops quite well, no unreasonable pedal pressure required.
     
  12. oj
    Joined: Jul 27, 2008
    Posts: 6,225

    oj
    Member

    I believe the brakes themselves are ok, remember they are designed more to stop a racecar at 160ish but should stop us fine at 55. Stick a cast iron GM corvette style MC on it, do away with thier proportioning valve for the moment and try it out. If the brakes work then add a stock type GM combination valve.
    Did the tech tell you the only way the MC would work is by having the pushrod going straight in, it can't be on the slightest of angles? which is a physical impossibility if connected to a brake pedal traveling on an arc.
    I think a lot of it is their prop valve, I think it is designed to protect the car when slamming on the brakes on a roadrace course entering a tight turn from the main straight, when you bled the rear brakes did you get just a minor spurt that ended abruptly with little volume?
     
  13. 55Thunderboy
    Joined: Mar 27, 2009
    Posts: 356

    55Thunderboy
    Member
    from NYC

    Dude you got the same answers i have, yeah they said the pushrod has to be "perfect" meanwhile why is there a clevis and ball on the end to articulate, it can never be straight in on any car i can imagine. I also have a funny feeling on their prop valve, for some odd reason we are getting more PSI on the rears than the fronts, no idea what causes this but the lines are all mounted correctly. I had issues with their masters in the past, lots of metal shaving over time so i ditched using them but they swore up and down to my friend he has to use their master and prop valve for the kit to function correctly.

    On a hard stop we get the rears to lock up but not the fronts FYI

    now when we pressure bled it using the Motive we left the prop valve fully open and started with the left rear wheel and so on, the fluid moves out back great, up front it seems to be sluggish but then again it all ties into that stupid prop valve they offered with the kit. I have a few ford mc in my garage that are 1 inch bore but i would need to make all new lines. I am more inclined to rip out the Wilwood Pro Combination valve first as a test and see if things get way better or not.

    Does anyone have a recommendation in a new pro combo valve to try, maybe SSBC?
     
    oj likes this.
  14. V8 Bob
    Joined: Feb 6, 2007
    Posts: 2,564

    V8 Bob
    ALLIANCE MEMBER

    There's really no way the rears can have more pressure than the fronts, but higher pressure may be needed to lock up the fronts, and the reason for the "stupid" prop valve, to keep the rears out of lock.
    If your rears are sliding first with the prop valve fully maxed out or CW, back off the valve CCW one or two turns at a time until the fronts slide first.
    Those new disc pads are normally low in effectiveness and should be burnished before any prop valve/axle balance work, unless they are pre-burnished or scorched.
     
    Last edited: Jun 7, 2017
  15. 55Thunderboy
    Joined: Mar 27, 2009
    Posts: 356

    55Thunderboy
    Member
    from NYC

    my buddy called wilwood tech again today, they sold him a pressure gauge so we can test psi at the master and calipers to see what is actually happening, no idea what the psi should be but il report back in a few days here with the results.
     
  16. 55Thunderboy
    Joined: Mar 27, 2009
    Posts: 356

    55Thunderboy
    Member
    from NYC

    hey guys we just put the PSI gauge on the front and rear calipers and we def found something WAY off. The front brakes are getting 600PSI at moderate leg pressure and only 800 with full leg pressure. Out back the rear calipers make 750-800 moderate leg pressure and 1200-1250 at full leg pressure. that is a substantial difference front and rear. We left the prop valve adjusted a touch closed. When we fully opened the prop valve the rears jumped to 1300+PSI with full leg pressure.

    We don't have fittings to plug the gauge into the master cylinder and we both would like to, need to run to hardware store tomorrow to see if we can get some NPT to flare unions for the master.

    Once we test the PSI on the master and if the results show the same bias i am simply going to swap the lines from the prop valve to the master on the front and rear circuits, that def would solve this braking issue i think.

    any of you got some ideas on what to check and as to why there is such a huge bias in pressure for installing all brand new parts? Can the 3/16 hardlines have bad flares from the Classic Tube kit we used? maybe the prop valve is the biggest POS as others have commented.
     
  17. Are the brake circuits oriented properly at the master cylinder? For some models at least, the front brakes are connected to the rear port of the master cylinder and the rear brakes connect to the front port. Not familiar with how Wilwood's m/cyls are designed. It would be interesting to see the pressure readings directly from the master cylinder.
     
  18. 55Thunderboy
    Joined: Mar 27, 2009
    Posts: 356

    55Thunderboy
    Member
    from NYC

    Here is the master prop combo, it comes with CNC bent lines so it can only go one way. Check this Wilwood tech support swore to me and my buddy several times that the tandem master is 50-50 between front and rear chambers. well what does this mean in their description, "The stroke is set at 1.10” with a volume ratio of 2:1 between the primary and secondary chambers" They call the Primary chamber the front, secondary the rear.

    Now working on Fords for a long time the rear chamber always was for the front discs and the front chamber for the rear drums, i hear GM is the opposite but EVERY aftermarket vendor from Wilwood, SSBC and Baer all say their masters are 50/50 and you can hook it up whatever way you like.
    well its obvious this isn't the case and the Wilwood guys have little to no knowledge because their website descriptions says otherwise.

    I can not wait to test the PSI at the master if i can find the NPT to NPT union locally tomorrow. We will get to the bottom of this soon enough, gotta get some new line material,maybe a new prop valve and a brass T for the front circuit but first need to test at master.
     

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  19. Ford blue blood
    Joined: Jan 4, 2009
    Posts: 604

    Ford blue blood
    Member

    That valve body under the master has a slide plunger in it to one turn on the brake warning light and two to seal off the offending section. Sounds like during the bleed process that slider is pushed to block off the front system. Use an ohm meter and see if the warning light switch is tripped. Many times it can be reset buy jamming hard on the peddle, might have to slowly bleed the rears until the switch turns off.
     
  20. B.A.KING
    Joined: Apr 6, 2005
    Posts: 3,582

    B.A.KING
    Member

    Question? Would taller/larger rear tires make you have mechanical advantage with a 50/50 MC. Now i am really old school but are the brake pads the metallic type? If so would they not stop real good until they got hot? Just old man thinking??
     
  21. 55Thunderboy
    Joined: Mar 27, 2009
    Posts: 356

    55Thunderboy
    Member
    from NYC

    We just tested PSI at the master and Wilwood is so full of crap how its 50/50 per chamber no freaking way. We bypassed the entire system and plugged the PSI gauge into the master ports while plugging off the other chamber here are the results

    Front Chamber which we were told is primary and for the fronts produced 900-1000 PSI MAX
    Rear Chamber which we were told is for the rears produced 1300-1500 PSI MAX

    this is def in line with what the PSI gauge was depicting at each caliper we tested.

    this is a substantial bias in PSI, we are thinking of just making new lines from the Prop Valve to the Master to switch this and see if this solves the braking issues we are having, such a PITA to make small lines that way by hand.

    I honestly want to scrap this MC and prop valve but my buddy paid so much dough he just cant afford to replace parts now.
     
  22. 55Thunderboy
    Joined: Mar 27, 2009
    Posts: 356

    55Thunderboy
    Member
    from NYC

    brake lights arent on but after seeing the PSI at the master i think it kinda makes sense now and Wilwood to say its 50/50 is nonsense
     
  23. V8 Bob
    Joined: Feb 6, 2007
    Posts: 2,564

    V8 Bob
    ALLIANCE MEMBER

    There is no pressure differential function in that combo valve, only a simple brake light pressure switch. You're thinking of some OE combo valves that some people claim have that blocking off function. :)
     
  24. V8 Bob
    Joined: Feb 6, 2007
    Posts: 2,564

    V8 Bob
    ALLIANCE MEMBER

    The only ways a single bore dual master would have unequal output pressure when port plugged is either air, or internal leakage between the primary and secondary circuits.
     
  25. oj
    Joined: Jul 27, 2008
    Posts: 6,225

    oj
    Member

    It might have a metering device under that Allen screw between the front brake circuit outlets.
    If there were leakage between primary and secondary the pressure would equalize wouldn't it? What about the compensating ports, if the primary circuit port is too far forward it wouldn't get enough fluid to create the pressure. When I tried to use those MC's I had the opposite problem, no rear brake pressure/volume.
     
  26. V8 Bob
    Joined: Feb 6, 2007
    Posts: 2,564

    V8 Bob
    ALLIANCE MEMBER

    Web description does not state any metering, and a push/pull bypass would would be obvious.
    You're correct, the pressure differential would eventually stabilize but could take more time than a quick
    pressure check.
     
  27. oj
    Joined: Jul 27, 2008
    Posts: 6,225

    oj
    Member

    You've a lot of experience with brakes etc, I have a couple of those MC's if you want to test for us I'll send one out for your analysis.
     
  28. V8 Bob
    Joined: Feb 6, 2007
    Posts: 2,564

    V8 Bob
    ALLIANCE MEMBER

    Like I stated, either air or a defect. No way can there be a pressure differential from the (single bore) master, except for air, a defect, or a fluid displacement (volume) issue in the system.
    I appreciate the testing confidence, as I have personally tested many "faulty" dealer removed masters, and a damaged seal, casting porosity or machining debris was always the reason.
    Just to add, I ALWAYS disassemble any new/rebuilt master I use, to be sure the seals are good and no debris in the bore.
     
    Last edited: Jun 11, 2017
    dirt t likes this.
  29. Please post final outcome.
    Thanks for posting I've learned something new.

    Sent from my SM-G900V using The H.A.M.B. mobile app
     
  30. stimpy
    Joined: Apr 16, 2006
    Posts: 3,547

    stimpy

    I wish Honeywell still offered the school they had . I have dealt with the idiots at wilwood several times only to go back to Bendix's teaching and fix the problems.

    But some of the problems are the installers not wanting to listen to industry trained person vs a phone tech .
     

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