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Technical disc brake swap issue..still got a soft pedal

Discussion in 'The Hokey Ass Message Board' started by Vincentnova, Dec 2, 2018.

  1. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,284

    Kerrynzl
    Member

    The port nearest the "stepped bore" [against the firewall] goes to the front callipers
     
    Vincentnova likes this.
  2. Vincentnova
    Joined: Nov 6, 2015
    Posts: 62

    Vincentnova

    a slop ?

    everything is new . rotor and bearing . I jaked the car and front wheels doesnt have a play . I dont understand it should not change the camber . I aslo take mensuration beettwen the top caliper's braket and the rotor and bottom braket and rotor , and everything look fine.???
     
  3. s55mercury66
    Joined: Jul 6, 2009
    Posts: 3,719

    s55mercury66
    Member
    from SW Wyoming

    If you didn't do anything to change the camber, it can only be a wheel bearing issue. Something is wrong there. There was a thread on here a month or so ago about the same problem you have, with that being the problem. I'm not there to tear into it, but I bet you have the wrong bearings in there, causing the wheel to sit like that, and when you apply the brakes, it pushes the piston out, and when you let off the pedal, the wheel leans back like that, and pushes the piston in so far, that it takes all of your pedal stroke to push it back out.
     
  4. s55mercury66
    Joined: Jul 6, 2009
    Posts: 3,719

    s55mercury66
    Member
    from SW Wyoming

    I am thinking one or both of your wheel bearings are wrong for your spindle.
     
    Vincentnova likes this.
  5. X-cpe
    Joined: Mar 9, 2018
    Posts: 711

    X-cpe

    For the camber issue, did the kit come with new steering knuckles? If so run a dowel through the ball joint holes to represent the steering axis and see if the spindle is at the same angle to it on both the old and new knuckles. If you did any thing with the upper control arm make sure it doesn't have an aftermarket offset shaft.
     
  6. Vincentnova
    Joined: Nov 6, 2015
    Posts: 62

    Vincentnova

    it didnt came with a new steering knuckles . its a very basic disc brake kit
     
  7. Vincentnova
    Joined: Nov 6, 2015
    Posts: 62

    Vincentnova


    thanks a lot for this answer im gonna dig in it
     
    sunbeam likes this.
  8. Atwater Mike
    Joined: May 31, 2002
    Posts: 9,798

    Atwater Mike
    ALLIANCE MEMBER

  9. Vincentnova
    Joined: Nov 6, 2015
    Posts: 62

    Vincentnova

    if rotor is pushing back piston I would feel a heck of a vibration when braking when i drive it ? correct? because i did a test drive and dont feel it
     
  10. Who makes the disc swap kit? You should not have a camber issue like that with the rotors put on correctly. I always make sure the inner bearing (did it come with an adapter sleeve??) goes onto the spindle squarely, also check the outer bearing on the spindle, check both to see how they fit into the rotor races. You should be able to adjust the wheel bearings and have the rotor spin freely, no excessive top-bottom movement at all.

    Also with discs, after they are bled, you still have to manually at the pedal push the pads out so they are tight to the rotors. Cars with power brakes, I start it, manual brakes, engine off.
     
  11. s55mercury66
    Joined: Jul 6, 2009
    Posts: 3,719

    s55mercury66
    Member
    from SW Wyoming

    Not neccessarily.
     
  12. Vincentnova
    Joined: Nov 6, 2015
    Posts: 62

    Vincentnova

    well after doing again multiple experiment im still at the same point


    I had a piece of wood and steal in one caliper to check for difference but nothing

    I took a part the calipers to inspect the seals and they are not low drag calipers .

    i plugged off the master cylinder and i get a rock hard pedal.

    I tried different caliper...nothing
    I tried a different MC...nothing

    i bled the shit out of the system soooooo many time... i dont get it
     
  13. TRENDZ
    Joined: Oct 16, 2018
    Posts: 83

    TRENDZ

    Remove your calipers and see if the rotor wiggles. If you have the wrong bearings for the spindle, your rotors will move around.
    If the rotor is not 100% square to the caliper, fluid will be consumed by the caliper trying to clamp at an angle.
    If you truly had no camber before, you have serious mis-match of parts. Solve the camber issue, and the brakes will probably work just fine.
     
    31Vicky with a hemi likes this.
  14. Camber change can't be right. Does your inner bearing fit the spindle or kit supplied spindle adapter? Also; just about every disc kit I've installed, has came with one or both replacement bearing races shipped loose with the kit, which are to be changed out with the "factory" installed races in the rotor. Possibly missing, incorrect, or overlooked parts in kit.
     
  15. You have something weird going on, strip the calipers off and look at the rotors, make sure they spin by hand easily and have no rock to them. If something is very far off, you may not get the castle nut and cotter pin to align.
     
    54vicky likes this.
  16. 54vicky
    Joined: Dec 13, 2011
    Posts: 1,115

    54vicky
    Member

    I noticed in your first post you said you bled master with a syringe I do not know what you mean by that you need to learn how to bench bleed.as to the camber issue I think you have been given good advice on the bearings.the master probably has a built in residual valve as disc drum come that way so do not waste money buying residual valves they have their place just not here.if you do not bleed master you will never get brake pressure.
     
  17. Vincentnova
    Joined: Nov 6, 2015
    Posts: 62

    Vincentnova

    hi guys happy new years and sorry for late reply
    been super busy

    about the camber . i remember doing the spring on it just before . car was too low . may be ? changing the coil changed the camber . i dont work all the time on the car since im very busy .and may be i didnt see it...

    today i removed the front calipers from there brakets , put something in between the pads .press the pedal and still same result

    i also got pressure test for brakes and ddi a test
    front driver side 870 psi
    front passenger side 870 psi ( sometime a lit more)
    rear both 580psi

    does 870 enough for the front?
     
  18. '51Plymouth
    Joined: Jun 8, 2005
    Posts: 231

    '51Plymouth
    Member
    from York, PA

    That was me, it was last spring...time flies.
    I was having pad knock back due to bearing slop allowing rotor wobble. Everything bled great, pressure held at a stop. When I moved, the incorrect bearings were letting the rotor knock the pads all the way back into the calipers. After a pump or two, brakes were great until I moved again. Correct bearings solved all problems.
    Between the brake issue and the camber issue, I'd suspect this is the same thing.
     
    s55mercury66 likes this.
  19. Vincentnova
    Joined: Nov 6, 2015
    Posts: 62

    Vincentnova


    I did a test .
    the new bearing that came in kit look exactly the same as the old one with drums
    I install the old bearing with the rotor and nothing changed

    should the bearing be different drum to disc ?
     
  20. Vincentnova
    Joined: Nov 6, 2015
    Posts: 62

    Vincentnova

    here a picture. How i blocked off caliper. Both side.
    It should eliminate the question about the rotor/camber

    I still got same pedal..
     

    Attached Files:

  21. s55mercury66
    Joined: Jul 6, 2009
    Posts: 3,719

    s55mercury66
    Member
    from SW Wyoming

    Yes, that should eliminate that as an issue. Hopefully one of the wiser folks will know about the line pressures.
     
  22. 427 sleeper
    Joined: Mar 8, 2017
    Posts: 665

    427 sleeper
    ALLIANCE MEMBER

    Is it possible that the master cylinder bore is too big? Could be that it has plenty of volume but not enough pressure, causing a soft pedal??? Just a thought. The camber issue really worries me though.
     
  23. Vincentnova
    Joined: Nov 6, 2015
    Posts: 62

    Vincentnova

    i think??? tell me if im wrong..
    bore too big , hard pedal and less braking
    and smaller bore more pressure and more pedal travel...

    any idee on that one?
     
  24. 427 sleeper
    Joined: Mar 8, 2017
    Posts: 665

    427 sleeper
    ALLIANCE MEMBER

    I was taught the complete opposite but that doesn't mean my teacher was right...
     
  25. 427 sleeper
    Joined: Mar 8, 2017
    Posts: 665

    427 sleeper
    ALLIANCE MEMBER

    When PHR converted Project X to disc brakes all they did to the master cylinder was to take it apart, and drive a drift pin through the residual valve to disable it and then they put it back together. A stock tri-5 Chevy has a 7/8" bore master cylinder. Never heard any negatives, but that could be propaganda also. Sometimes too much is too much.
    My personal opinion is that a big resivoir,or however the hell you spell it, is great for the supply side of the equation, but the pressure is determined by the bore size.
     
    Last edited: Jan 12, 2019
    RAR1947 and Vincentnova like this.
  26. TRENDZ
    Joined: Oct 16, 2018
    Posts: 83

    TRENDZ

    Larger bore master will have a higher/ stiffer pedal if everthing is working correctly. The larger the bore, the less pressure will be applied to the caliper with a given force on pedal application.
     
    mad mikey and Vincentnova like this.
  27. ^^^this is correct


    Sent from my iPhone using H.A.M.B.
     
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  28. Vincentnova
    Joined: Nov 6, 2015
    Posts: 62

    Vincentnova

    ok next step im going to check what master bore size i have and i will go bigger and see
     
  29. 427 sleeper
    Joined: Mar 8, 2017
    Posts: 665

    427 sleeper
    ALLIANCE MEMBER

  30. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,284

    Kerrynzl
    Member

    That is correct
    bore too big , hard pedal and less clamping pressure [unless assisted]

    A quick way to test to see if you bore size is too small is to eliminate a calliper.
    Clamp off one hose and test for pedal travel.
    It should come up.

    Also clamp off the rear hoses, and try it
    I've had new brake shoes that were the wrong curvature for the drums .They adjusted up nicely for drag on the drums, but pedal pressure would push/compress them even further.
    Grinding them to the shape of the drums was the solution.
     

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