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Posted By Discussion Topic: 1947 brakes -- page: 1 2     cdeac47 09-07-2020 @ 10:22 PM reply profile send p.m. Member Posts: 37 Joined: Apr 2020 I am working on a '47 2 door sedan with a flat head V8. It's not modified! I have replaced the 2 front slave cylinders, replaced the front drums and shoes as well as the brake cables. In the rear I have turned the drums, replaced the 2 slave cylinders. When I arc'd the brake shoes I made the radius of the shoe closer to radius of the drum than I do on a GM car with bendix brakes. I inspected the master cylinder which appears okay and then filled it and bled the braking system 3 times! I adjusted the shoes/drums as well. On the hoist I was able depress the pedal and found that point of contact, shoes to drum, to be very low; almost to the floor. Hesitantly I went for a road test and the brakes did stop the car. Then I tried an aggressive stop and the pedal went to the floor and the brake stopped the car but by no means did it feel like a panic stop as they did not lock up the wheels and by no means did the car skid! Once the pedal was on the floor the pedal became numb and the car stopped. What am I missing because a lot of the brake system is new! I question if there is an adjustment needed at the brake pedal linkage. HELP!!! juergen 09-08-2020 @ 5:59 AM reply profile send p.m. Member Posts: 254 Joined: Jan 2010 Did you measure the ID of the drums? If you are using standard linings (3/16), the drums should be cut less than .060 or you will not have a lot of lining contacting the drum even if you arched the shoes as the fixed pivot won't get the bottom of the shoes close to the drum. Also if the brake pedal is soft and nearly hits the floor when depressed, you still have air in the system. TomO 09-08-2020 @ 8:35 AM reply profile send p.m. Senior Posts: 7244 Joined: Oct 2009 The common causes of a hard, low brake pedal are the ones that juergen mentioned as well as shoe adjustment and master cylinder push rod free play (1/4"). Worn pedal shaft bushings could also cause this. The brake shoes should be adjusted by adjusting the forward shoe cam counter clockwise until the drum cannot be turned by hand, then back off just enough so the drum can be turned by hand, without drag. Then do the same to the rear shoe. Is this how you adjusted yours? Did you put the short shoe to the rear of the car? This is opposite of the way you would install them on self energizing brakes like those found on GM cars and later Ford products. Did you have good pedal before you replaced the wheel cylinders? Did you check to see if all 4 wheels are braking at the same time? Let us know how you made out. Tom This message was edited by TomO on 9-8-20 @ 8:37 AM cdeac47 09-08-2020 @ 11:41 AM reply profile send p.m. Member Posts: 37 Joined: Apr 2020 The front drums measured too wide and I replaced them. The rear drums were still within spec so I cut them and used them. Two of four slave cylinders were leaking so I replaced all 4 of them. The shoes are properly installed. The shoe were arc'd tightly and barely rocked when I test fit them in the drum. The adjustment on each of the 4 brake assemblies are very tight therefore a small amount of drag can be felt when turning the wheel. The brakes have been bled on three occasions. So I believe I have the obvious things in good order. Now I am looking for the not so obvious things. Can you elaborate on the master cylinder push rod free play and the pedal shaft bushings? This message was edited by cdeac47 on 9-8-20 @ 11:45 AM 1931 Flamingo 09-08-2020 @ 11:54 AM reply profile send p.m. Member Posts: 383 Joined: Nov 2019 Worn bushings and incorrect push rod play ='s lost motion. Paul in CT 40 Coupe 09-09-2020 @ 5:42 AM reply profile send p.m. Senior Posts: 1650 Joined: Oct 2009 Adjust the brake shoes so they all drag slightly and evenly. TomO 09-09-2020 @ 8:05 AM reply profile send p.m. Senior Posts: 7244 Joined: Oct 2009 There should be 1/4" free play, measured at the top of the pedal, before the master cylinder push rod contacts the piston in the master cylinder. Too much free play will result in a low pedal. Worn pedal shaft bushings will allow the pedal to travel without operating the piston. Did you use the stepped wheel cylinders or all one size cylinders? Tom supereal 09-10-2020 @ 1:23 PM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 It is likely that the system has not been completely bled. Bleeding these cars can be difficult without a bleeder unit. With the master cylinder lower than the wheel cylinders, it takes time and extra fluid if you are using the "pedal pump and hold" method. As my friend Tom O suggests, be sure the pedal free play is correct to allow the system pressure to release when the pedal is completely released, and the reservoir is kept full as you bleed the system. When I bleed my '47, it usually takes lots of fluid, even with DOT3. If you are trying to install silicone fluid, it is almost impossible without a bleeder. Even then, the pedal can be softer when completed. Unless you have removed more than .060 when turning the drums, arcing the shoes may not be needed. cdeac47 09-10-2020 @ 6:42 PM reply profile send p.m. Member Posts: 37 Joined: Apr 2020 Tom: I used stepped cylinders. I am new to the Ford way of doing things. Therefore the question arises can you please elaborate on the pedal shaft bushings? A quarter inch of pedal free play would be a fantasy for me. The brake pedal does not seem to have any resistance until it travels at least half way down. There's just not enough pedal travel and hits the floor and the brakes never lock up. I used an air driven brake bleeder 3 times and it did use quite a bit of fluid. It's a fun car to drive if only I can get it to stop! This message was edited by cdeac47 on 9-10-20 @ 6:53 PM alanwoodieman 09-10-2020 @ 7:40 PM reply profile send p.m. Senior Posts: 864 Joined: Oct 2009 make sure there is clearance in the brake pedal-you just need the pedal rod to "rattle" you really don't need a 1/4" I have been using my homemade bleed jar for over 40 years with better results that power bleeding the system--take a glass jar and punch a hole into the top, place a piece of metal brake tubing in to the hole and with a j bend at bottom-use some jb weld and seal off the tube, fill jar with clean fluid until the j bend is under the fluid-hook up a rubber hose to the bleed and to the bleed jar tubing and open bleeder and slowly-READ SLOWLY-move the pedal up and down, using this method you are sure to bleed air out and fluid in with every pump. I do this with the car jacked up and just me pulling on the brake pedal arm from under the car

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