Modified Brakes

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ctcarguy
Posts: 17
Joined: Fri May 08, 2015 3:13 pm

Modified Brakes

Post by ctcarguy »

The previous owner of my 56, upgraded to front disc brakes. When someone else does the work, it is hard to tell if it was done correctly. I don't think so in this case. The front section of the dual master cylinder feeds directly to the rear brakes. The rear section feeds into the power booster (stock) and then the front brakes. There is no proportioning valve at all. The car stops but I think it is working off the rear brakes only and the pedal travel is almost to the floor. As I remember 50's power brakes, they were sensitive, these require pressure.
From what I have read so far and my knowledge of brakes:
1. System needs a proportioning valve
2. The front section of the master cylinder should be for the front brakes and the larger rear section for the rear brakes
3. The power booster may or may not be working but should be part of the front brakes only.

Before I rip apart what is there, I want to be sure I am on the right track. Thanks

(Moderator moved this post to the more appropriate Modified section)
Joe Johnston
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Re: Modified Brakes

Post by Joe Johnston »

Always good to ask questions before tearing things apart and getting into trouble or spending a lot of money needlessly.
Not in any particular order:
The Largest volume reservoir of the master goes to the disk brakes because disk brakes require more brake fluid as the pads wear and pistons extend. The rear section is usually the larger and often the bore of the piston is larger in the rear so this makes machining a lot easier during manufacture. Yours is correct.

The line from the rear of the master should go to the booster, and again yours is correct, but your booster my not be functioning to its max ability. These disk conversions only use the booster for the front disk brakes. The Midland boosters do work but don't expect them to work as well as a modern car or truck because the area of the diaphragm is less and the effective boost is less than we have now. I have a disk conversion and have left the booster out of the circuit and the manual brakes work quite well, but pedal effort is a little higher. Pedal is firm and probably goes halfway of the travel to the floor. Adjusting procedures for rod that goes from the pedal arm to the master cyl should be in the manual. Perhaps you need a minor adjustment.

The front section should go directly to the rear brake drums.

In some cases, Ford used manual and power disk/drum brakes WITHOUT a proportioning valve and were able to do so because the piston in the master cylinder is matched to the proper disk brake calipers and rear wheel cylinders. Everything is sized as a system and works well. Often these conversions were done with a kit from one of the Thunderbird parts suppliers and it will be a complete package and I doubt you have any problems in that respect.

Some cars did indeed have more sensitive brakes than others, but that doesn't mean you should have a similar experience now. I've always felt that GM cars had a softer pedal feel than Ford products, but that is just my opinion.

Its simple to test everything, just hit the brakes hard on a stone driveway and you should be able to lock everything up. It also may be a good thing to change and flush the brake fluid and re-bleed the system, especially if the fluid in the master is a bit brown.

Hope that helps.
J
PLEASE invest a few bucks and buy all the shop manuals for your car. Definitely will save you much time and be an education.

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ctcarguy
Posts: 17
Joined: Fri May 08, 2015 3:13 pm

Re: Modified Brakes

Post by ctcarguy »

Excellent reply. Thanks. I will lengthen the brake rod and see if it helps. The car does not nose dive at all on braking unless the pedal is near the floor. It does seem to take a longer distance to stop than my 2 drum brake 65 Corvairs but it is also a lot more car. As far as the booster, i don't care if it is working as long as I do not need extreme pressure to stop. I have bleeding and changing the fluid on my Thunderbird to-do list. I bought the car for my wife but she is not comfortable driving it. I guess I have to grin and bear it and drive it! Just kidding, I am really enjoying cruising in this car. Very smooth ride and comfortable.
Larry
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paul2748
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Location: Northeastern New Jersey

Re: Modified Brakes

Post by paul2748 »

In adjusting the pedal rod, make sure that you leave 1/8 to 3/16 travel before it starts to push the piston in the master cylinder. This allows for fluid expansion when the brakes get hot.
1956 Fiesta Red 312
1954 Ford Victoria 312
1948 Ford Convertible Street Rod 302
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