Welcome to Club Hot Rod!  The premier site for everything to do with Hot Rod, Customs, Low Riders, Rat Rods, and more. 

  •  » Members from all over the US and the world!
  •  » Help from all over the world for your questions
  •  » Build logs for you and all members
  •  » Blogs
  •  » Image Gallery
  •  » Many thousands of members and hundreds of thousands of posts! 

YES! I want to register an account for free right now!  p.s.: For registered members this ad will NOT show

 
Like Tree9Likes
  • 3 Post By glennsexton
  • 2 Post By 34_40
  • 1 Post By 53 Chevy5
  • 2 Post By Hotrod46
  • 1 Post By motocop

Thread: Hot Rod braking problems
          
   
   

Reply To Thread
Results 1 to 8 of 8
  1. #1
    1929ModelA is offline CHR Junior sMember Visit my Photo Gallery
    Join Date
    Dec 2019
    Location
    Collins
    Car Year, Make, Model: 1929 Ford Model A
    Posts
    1

    Hot Rod braking problems

     



    New to this site and new to hot rods. Shade tree mechanic at best. Bought a car (1929 Ford Model A Fordor) already restored (retrofitted) with no knowledge of its components finished in 1981. But what I do know is the brakes are lousy. New master cylinder mounted on frame under driver floorboard. No vacuum or other power. Sits lower than calipers. Front calipers have one piston on Mustang II front end from 1978. Rear end is from 1979 Corvette and has four pistons. I do not know the size of the bore on the master cylinder or either caliper. It has an adjustable proportional valve plumbed to the rear brakes and Wildwood blue 2 psi residual valves plumbed front and rear. Excellent pads and rotors.

    The brake pedal is full and hard, not spongy but you have to press down hard to make it stop and it will coast to a stop with no skidding or throwing you thru the windshield.

    Does anybody see any problems with this setup that may help me short of disassembling the master cylinder and/or calipers and provide that information? Are the residual valves the right psi given the multiple caliper piston arrangement and would they be the problem? Are they needed?

    The pedal comes out of the floor, makes a 90 degree turn to the right (if you are sitting in it) then another 90 degree turn towards the driver. It does not appear to be binding in any way.
    Last edited by 1929ModelA; 12-03-2019 at 08:17 PM.

  2. #2
    glennsexton's Avatar
    glennsexton is offline CHR Member/Contributor Visit my Photo Gallery
    Join Date
    Mar 2005
    Location
    Tigard
    Car Year, Make, Model: 63 Nova SS
    Posts
    2,572

    Welcome to CHR!

    Might sound silly, but have you flushed and bled the lines? Sometimes crud grows in brake lines - especially if she been sitting for a while. Might be worth a shot.

    Regards, Glenn
    NTFDAY, johnboy and rspears like this.
    "Where the people fear the government you have tyranny. Where the government fears the people you have liberty." John Basil Barnhil

  3. #3
    34_40's Avatar
    34_40 is offline CHR Member Visit my Photo Gallery
    Join Date
    Sep 2007
    Location
    New Bedford
    Car Year, Make, Model: 34 Ford 3W Coupe Replica
    Posts
    14,606

    Welcome to the site. Maybe you could share a pic of the car with us?

    Have you even looked into the master cylinder? Like Glenn above, I'd be curious as to the color / condition of the fluid.

    I am also curious as to the brake pedal length. I wonder if the builder change the mechanical advantage during fabrication by making the bends to place the pedal where he wanted it.

    Could you measure the brake pedal? We's need to know the 2 distances from the pivot. Pivot bolt center to the connection to the master cylinder center and then pivot center to the pedal itself center.. The mechanical advantage is the "horsepower" you can input to the brakes hydraulic system.

    My other thought would be to lift the car completely off the ground and have a helper apply full pressure to the brake pedal while you try and turn each wheel. I'd be curious if any of them turn. Even if you used a long prybar ( like a diggers rock bar) off the floor and really work at making a wheel turn.

    Well, that's all I've got for now. We'll see what others come up with.
    NTFDAY and glennsexton like this.

  4. #4
    53 Chevy5's Avatar
    53 Chevy5 is offline CHR Member Visit my Photo Gallery
    Join Date
    Jan 2005
    Location
    Doon, Ia
    Car Year, Make, Model: 53 Chevy 3100
    Posts
    2,709

    Welcome, I'm also wondering if you don't have enough leverage on the pedal.
    NTFDAY likes this.
    Seth

    God cannot give us a happiness and peace apart from Himself, because it is not there. There is no such thing. C.S.Lewis

  5. #5
    Hotrod46's Avatar
    Hotrod46 is offline CHR Member Visit my Photo Gallery
    Join Date
    Feb 2007
    Location
    Vidalia
    Car Year, Make, Model: 1946 Ford Coupe, 1962 Austin Healey 3000
    Posts
    1,496

    Provided the brakes are in good mechanical shape, it sounds like low line pressure. Could be too large of a master cylinder bore or not enough leverage in the pedal or both.

    If I recall right, the original MII master was 7/8" bore. You need to shoot for at least 1000 psi with a leg effort around 100 lbs. Disc brakes require a lot of pressure.

    Here's a couple of online calculators that will help.

    https://www.markwilliams.com/calculators.html

    https://techtalk.mpbrakes.com/how-to...ng-pedal-ratio

    You could also have a mechanical issue. Stuck caliper pistons, stuck floating caliper (would only apply to the fronts), badly glazed rotors/pads, wrong pad material would be few possibilities.

    Edit: I was close on the MII MC bore. It's actually .937". 7/8 is .875.
    Last edited by Hotrod46; 12-05-2019 at 05:21 PM.
    glennsexton and 34_40 like this.
    Mike

    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc-
    I'm following my pass​ion

  6. #6
    glennsexton's Avatar
    glennsexton is offline CHR Member/Contributor Visit my Photo Gallery
    Join Date
    Mar 2005
    Location
    Tigard
    Car Year, Make, Model: 63 Nova SS
    Posts
    2,572

    Good call on the fluid - is it a nasty color or nice and clear?
    Last edited by glennsexton; 12-06-2019 at 08:53 AM.
    "Where the people fear the government you have tyranny. Where the government fears the people you have liberty." John Basil Barnhil

  7. #7
    Dave Severson is offline CHR Member/Contributor Visit my Photo Gallery
    Join Date
    Jul 2003
    Location
    Madison
    Car Year, Make, Model: '67 Ranchero, '57 Chevy, '82 Camaro,
    Posts
    21,160

    How much travel does the rod going into the master cylinder have? Generally speaking a pedal ratio of about 6:1 should be adequate, depending on the size of the master cylinder. One other thing to check is if the residual valves are installed correctly, there is an in and an out side to them. Was the master cylinder bench bled before it was installed. I don't mean to be insulting with dumb questions, but often the easiest things are overlooked and can cause major problems.
    Yesterday is history, tomorrow is a mystery, Live for Today!
    Carroll Shelby

    Learning must be difficult for those who already know it all!!!!

  8. #8
    motocop is offline CHR Member Visit my Photo Gallery
    Join Date
    Dec 2019
    Location
    Jonesborough
    Posts
    4

    I have a 1936 coupe with the same basic setup. 9.25" rotors in front and a Ford 8" in the rear. Mine stops as hard as my drum brake 57 Chevy. I dont think the small rotors cut it for stopping power. I plan on going to a 11" Wilwood setup. Its four piston and low profile so I wont have to go to a 15" wheel.
    Dave Severson likes this.

Reply To Thread

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
Links monetized by VigLink