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Technical New discs/drums & master cylinder but crappy brakes???

Discussion in 'The Hokey Ass Message Board' started by Crazy Legs, Apr 16, 2014.

  1. Crazy Legs
    Joined: Sep 3, 2008
    Posts: 266

    Crazy Legs
    Member

    Hey guys,
    Long story short, I’ve finally got my 54 Ford to be able to drive after 3 years and everything is good but it doesn’t seem like the brakes are very good on it for being everything new and non-powered and I can’t figure out why?

    A little history on the setup is on the front of the car I’m using new S10 discs, calipers, pads, braided lines and the rear is completely rebuilt early 1957 style 9” Ford (1-3/4” wide shoes) and all new parts inside and turned drums.

    New 3/16” lines, fed by a 65 non-powered mustang disc/drum master cylinder and a Wilwood proportioning valve to adjust front/rear bias.

    My issue is, I’ve got good pedal, and doesn’t bottom out on the floor or anything but it just doesn’t seem to stop very well. Pushing as hard as I can on the pedal it will not lock up the fronts or rears no matter where I have the prop valve. As I bring more pressure to the rears it does help the stopping but definently not as good as what I have experienced with manual brakes in the past.

    Last night I took it out on the road and about 60mph I stopped as quickly as possible and once it finally stopped the front rotors/pads were smoking so I know the fronts are working but they just don’t seem very good…….

    Could it be I’ve still got air in the lines?
    Could the master cylinder be too small of bore?

    Thanks in advance!
     
  2. Larry W
    Joined: Oct 12, 2009
    Posts: 728

    Larry W
    Member
    from kansas

    Did you bench bleed to M/S before putting on the car?
     
  3. landseaandair
    Joined: Feb 23, 2009
    Posts: 4,386

    landseaandair
    Member
    from phoenix

    Sounds like either pedal ratio or to big a bore in the master. Mustang might be 1"?, may need 7/8"? Wouldn't mess with pedal ratio unless the master can easily be put inline with pedal hole.
     
  4. DD COOPMAN
    Joined: Jul 25, 2009
    Posts: 1,121

    DD COOPMAN
    Member

    NO, but is is POSSIBLE that the M/C has too LARGE of a bore for the calipers, and even the rear wheel cylinders.

    SMALLER the M/C bore equals MORE effective pressure (and more pedal travel) for the same displacement of fluid to the calipers and W/Cyls. DD
     
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  5. V8 Bob
    Joined: Feb 6, 2007
    Posts: 2,589

    V8 Bob
    ALLIANCE MEMBER

    The '65-'66 Mustang disc/drum single system master cylinder has a 15/16" bore, while the '67-'72 dual system master has a 1" bore. Which one do you have?
     
  6. Crazy Legs
    Joined: Sep 3, 2008
    Posts: 266

    Crazy Legs
    Member

    Ok great responses!
    Yes I bench bled M/C
    Yes wiped down rotors, originally started with prop valve all the way out = only 57% power goes to rear
    It is a dual reservoir master cylinder
     
  7. V8 Bob
    Joined: Feb 6, 2007
    Posts: 2,589

    V8 Bob
    ALLIANCE MEMBER


    All the adjustable prop valves I've worked with or use increase rear pressure when screwed "in". The arrow on the knob will/should indicate pressure increase to the rears.
    Keep in mind the rear brakes receive full master cylinder pressure until the crack or split point is reached with a prop valve, then a percentage (57% in your case) of MC pressure is delivered from that point higher. The adjustable feature moves the crack/split point up or down, usually from around 100 psi to about 1000 psi.
    As suggested earlier, new brakes need to be "burnished" or "bedded" for maximum effectiveness. Normally, 20 to 30 medium decel stops from 40 MPH with about 1 mile intervals for
    cooling will do the job. :)
     
  8. Bruskie
    Joined: Apr 9, 2014
    Posts: 50

    Bruskie
    Member

    Did u use quality pads on the front? Makes a big difference.
     
  9. Crazy Legs
    Joined: Sep 3, 2008
    Posts: 266

    Crazy Legs
    Member

    V8 bob, Yes my prop valve is the same way.
    I've got 12 miles on the car total so sounds good on the proper break in, will do that and see what happens.
    Just a "brake best thermo quiet" brand , not the best but had worked fine on my other heaps
     
  10. I wonder how much of what you're feeling is due to the fact that you have manual brakes with front discs. The few vehicles I've driven with manual disc/drum brake set-ups never really impressed me. Manual four wheel self-energizing drum brakes always felt better to me.

    Most of the brake bias is on the front wheels, and disc brakes don't self-energize like most 60's and newer drum brakes do. Try the break-in procedures mentioned above and that may help the feel of the brakes. Or you might want to consider adding a booster if you're locked in to the front disc set-up.
     
  11. txturbo
    Joined: Oct 23, 2009
    Posts: 1,771

    txturbo
    Member

    Check the rear shoes and see how much contact area you have. If the drums were turned quite a bit your shoes may only be contacting a couple inches of drum surface in the center. If thats the case you will have to re-arch the shoes.
     
  12. Ulu
    Joined: Feb 26, 2014
    Posts: 1,748

    Ulu
    Member
    from CenCal

    Sounds to me like you have a "short" pedal from a power brake car on a car with manual brakes. You should be able to lock 'em up even without a booster, if the pedal is "long enough". (Has the correct leverage ratio.)
     
  13. hayu
    Joined: Feb 8, 2010
    Posts: 30

    hayu
    Member

    Also make sure rear are adj. up good.
     
  14. Crazy Legs
    Joined: Sep 3, 2008
    Posts: 266

    Crazy Legs
    Member

    Yeah I hear ya on the disc/drum vs drum/drum, my dad's Chevy II is drum/ drum and stops way better than this car.
    I'll check all pads, shoes etc and do the break in etc and report back, thanks everyone

    Btw
     
  15. If your master is for a '65 Mustang disc/drum those were 4-piston calipers. I know on some older GM ('67-68 Impala) cars with 4-piston calipers, the masters were different and wouldn't interchange for a single piston caliper application.

    Size-wise the Mustang may be a little lighter than your '54. I would try a master off a '70ish Torino as it may give you a better front-back balance. Do you have room for a power booster?

    But I would first change to a master that is closer to your car's weight and general proportions, also agree on ditching the proportioning valve.

    Bob
     
  16. Bruskie
    Joined: Apr 9, 2014
    Posts: 50

    Bruskie
    Member

    Buy a good set of wagner or raybestos semimetalic pads & see how they work
     
  17. 1971BB427
    Joined: Mar 6, 2010
    Posts: 5,563

    1971BB427
    Member
    from Oregon

    Not sure the Wilwood prop valve was a good choice with the factory disc-drum master. I'm still interested in what year master it is, and what your brake pedal ratio is? Measure from the pivot point to the middle of the brake pedal, and the pivot point to the operating rod attachment point. Post the info so we can determine if you've got enough ratio to work that master.
     
  18. Bruskie
    Joined: Apr 9, 2014
    Posts: 50

    Bruskie
    Member

    if the pads were smoking there is an issue with contamination or crappy pads
     
  19. ^^ding ding^^

    Pushing as hard as I can on the pedal it will not lock up the fronts or rears no matter where I have the prop valve


    So this pushing is either bottoming out the master, Your pedal ratio is off
    Or you have some water contamination
     
  20. Crazy Legs
    Joined: Sep 3, 2008
    Posts: 266

    Crazy Legs
    Member

    Interesting on the 4 piston calipers vs these S10 calipers
    I hear ya on the other brand pads, I may try that
    Why is the adj prop valve a bad idea? Isn't that the best situation cuz its all adjustable?
    Not sure what the pedal ratio is but its using the stock hole in the pedal, I'll check it
    Bruskie, I thought it was weird as well that they were smoking, I've never seen that either, I'll clean and check it all asap.
    Its not bottoming out on anything, if I was HE-Man I could push the pedal even farther. How could there be water contamination? Its 100% new, new fluid & it lives in a heated/air condition garage?
     
  21. Glycol-ether (DOT 3, 4, and 5.1) brake fluids are hygroscopic (water absorbing), which means they absorb moisture from the atmosphere under normal humidity levels. All you need to do is leave the system open or the container.

    Hydraulics are based on ratios of leverage, just like a lever and fulcrum only with a twist.
    A larger bore moves more fluid but its harder to move it.
    A smaller bore it easy to move but the amount moved is less.

    Then the pedal is a basic lever and fulcrum.
    The master stroke is "x" and with a pedal ratio of X you'll stop nothing.
    If your pedal ratio is 3x you are applying 3 times the force but moving 3x as far.
    If your pedal ratio is 6x you are applying 6 times the force but moving 6x as far.
    Manual brakes usually have a high pedal because they need a big ratio and plenty of room to move.
     
    Last edited: Apr 17, 2014
  22. When you locked them up, did it give off that hot brake pad smell? Still quite possible the backs weren't working nearly as well as the fronts. Again, the master is off a car that is very light in the ass.

    How many S10 parts do you have around, like the master and pedal arm? Not to use the pedal arm, but measure from the pivot to the pedal to get an idea of the ratio. I would definitely consider using the S10 master, at least to de-bug things.

    Bob
     
  23. fms427
    Joined: Nov 17, 2006
    Posts: 864

    fms427
    Member

    Manual disc systems aren't really very good, except with really light cars with really big brakes - not your car.....

    If I remember correctly, the 1978 GM intermediate cars offered manual discs on a very limited number of cars (same front brake as you have) - 7/8 master, 6.5 :1 pedal - passed federal standards but was a pretty crappy system - high pedal travel and required a lot of effort. (Yeah, I was the engineer on those systems, and even I didn't like it ....):D

    Check your pedal ratio - should be 6-7 to one - and master about 7/8. Get some GOOD pads. like a racing pad like HAWK - may give you an acceptable car. And use all the rear brake you can - but watch out for rear brake lock-up on slippery roads)

    But I would REALLY recommend a booster (about 4:1 pedal and 1" master...) . You will be much happier.....
     
  24. Ulu
    Joined: Feb 26, 2014
    Posts: 1,748

    Ulu
    Member
    from CenCal

  25. Ulu
    Joined: Feb 26, 2014
    Posts: 1,748

    Ulu
    Member
    from CenCal

    You say you have "good pedal" but how firm is the pedal?
    If there's air (or steam) in the lines it'll feel spongy.

    If it's rock hard under pressure, there's no air.

    Have you tried to back-bleed the brakes?
     
  26. telekenfun
    Joined: Mar 9, 2010
    Posts: 250

    telekenfun
    Member

    You should have no trouble locking up the rears with the setup you have. TXTurbo has made a very good point. Shoe re-arching machines are almost nonexistent anymore. On my 54 GMC with a V6 Citation vacuum booster MC (disc/drum) and front ASTRO van/stock rears, I had to adjust the rears every couple of days until the shoes wore down to make full contact. Now I only need to adjust them once a year, and feel every bit as good as my modern daily driver. The first clue will be rapid loss of pedal height before braking action begins. Your pedal should be rock hard an inch from the top. Adjust a bit of drag on the rear shoes and get the slack out of rod between the pedal and the master cylinder.
    By all means switch to a vacuum booster setup, in todays traffic you don't have time to double pump the brakes!
    Best Regards and Good Luck with all your endeavors, KB.
     
  27. 34toddster
    Joined: Mar 28, 2006
    Posts: 1,481

    34toddster
    ALLIANCE MEMBER
    from Missouri

    I had an issue like this, found out the rear drum wheel cylinders were too big for my master cyl., 9 in Fords offered several diameter rear wheel cylinders I used the smallest I could find, 7/8 I think, I could then lock up the rear brakes in a panic stop. I also had a adj prop valve, didn't seem to do much until I changed the rear wheel cylinders. That is the only thing I changed and it helped a lot.
    Good luck!
     
  28. Limey Steve
    Joined: Apr 4, 2005
    Posts: 1,523

    Limey Steve
    Alliance Vendor
    from Whittier

    Remove the proportioning valve , put a connector between the two lines , re bleed & see what happens, my money is on good brakes , I never use an adjustable prop valve, why take away rear brakes . Try it & see what happens I have fixed many systems that have your symptoms by just removing the valve.
     
  29. Ulu
    Joined: Feb 26, 2014
    Posts: 1,748

    Ulu
    Member
    from CenCal

    Because the rear ends of some vehicles (Light rods and coupes with truck engines under the hood) are so light they'd skid all the time.

    Most modern cars are proportioned heavily toward the front due to that; plus, the issue of weight transfer under braking is a big deal.

    The thing with the OP is that his brakes are so weak presently, relative to the car's weight, that there's no chance of it swapping ends under braking.

    He will probably need one when the power booster is restored.
     
  30. LOL! :eek: Ahaaa! So YOU were at least partially responsible for some of those systems, eh? The early S10s with manual disc/drums would sure get your attention on a hard stop. At least if you had a manual trans you could scrub off some speed by downshifting. The Vegas and Monzas with this set-up were no day at the beach either! :D
     
    Last edited: Apr 18, 2014

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