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Old 07-11-2020, 02:07 PM   #1
farmerdick
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Default 40`Ford Brakes Update from 7/10 post

I was reading some early posts on brake problems and noted a situation where the master cylinder was below the wheel cylinders which mine is. Any thoughts?
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Old 07-11-2020, 06:06 PM   #2
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Default Re: 40`Ford Brakes Update from 7/10 post

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Originally Posted by farmerdick View Post
I was reading some early posts on brake problems and noted a situation where the master cylinder was below the wheel cylinders which mine is. Any thoughts?
Problems? I'd never encountered any. I've been "playing" with these old Fords for decades.
Kind of a pain to access the master but other than that no issues at all. Keep in mind that millions, literally millions of cars were built this way.
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Old 07-11-2020, 06:20 PM   #3
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Default Re: 40`Ford Brakes Update from 7/10 post

On a stock brake system they were designed this way and work fine. On some modified systems using a mixture of parts, a master cylinder mounted lower than the wheel cylinders can cause issues. This is more often prevalent with disk brakes than drum brakes.
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Old 07-12-2020, 06:33 AM   #4
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Default Re: 40`Ford Brakes Update from 7/10 post

I just can not get a firm pedal without it traveling 3 to 4 inches and stopping 2 inches from the floor boards. I`ve bleed the master cylinder twice and bleed the lines 3 times with clear fluid, no air bubbles.
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Old 07-12-2020, 07:03 AM   #5
richard crow
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Default Re: 40`Ford Brakes Update from 7/10 post

is the pedal hard or spongy if it,spongy air in system. if it,s hard it,s a adjustment problem of some kind. master push rod ,shoe anchor adj. cam adj to name a few
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Old 07-12-2020, 12:32 PM   #6
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Default Re: 40`Ford Brakes Update from 7/10 post

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There is a valve in the master cylinder that keeps the wheel cylinders from bleeding back into the master cylinder.
Do you get a better pedal with the hand brake on? If so then the rear shoes need more adjustment.
Adjust all 8 shoes right up tight and see if you get a good pedal.
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Old 07-12-2020, 12:50 PM   #7
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Default Re: 40`Ford Brakes Update from 7/10 post

Are you using a stock Ford master cylinder with a 1-1/16" bore? A smaller bore will provide greater line pressure for the same applied "foot force" but more stroke before the displaced line fluid pushes the wheel cylinders and shoes to the contact point.
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Old 07-13-2020, 09:25 AM   #8
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Default Re: 40`Ford Brakes Update from 7/10 post

As Aarongriffey said adjust your brakes. Then see how much freeplay there is until the push rod starts bushing the inards ofmaster cylinder in. You may need to adjust the push rod so it just has a little play and just making contact with the inards of the master cylinder. JMHO.
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Old 07-13-2020, 04:12 PM   #9
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Default Re: 40`Ford Brakes Update from 7/10 post

I am using a 67` mustang MC which has a 1" bore. I also checked the pedal ratio and is 5:1. Herd that it should be 6:1.
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Old 07-13-2020, 04:15 PM   #10
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Default Re: 40`Ford Brakes Update from 7/10 post

The pedal has some resistance for about 3" then gets hard 2" from floor.
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Old 07-13-2020, 09:38 PM   #11
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Default Re: 40`Ford Brakes Update from 7/10 post

Brake shoe adjustment is everything before you can hope for correct pedal travel. Keep working on the adjustment.
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Old 07-14-2020, 08:52 AM   #12
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Default Re: 40`Ford Brakes Update from 7/10 post

Hi Farmerdick,


The 1" bore shouldn't stroke much more than the stock 1-1/16" bore. I think some of the Mustangs had a 7/8" bore. The 67 is a dual bowl type. For disk brakes in the front circuit, there is a residual pressure check valve which maintains about 2psi. For the drums in the back circuit there is a 10psi check valve. You may want to think about adding a 10psi valve for the front drums. This won't effect the stroke to brake application though that you have.


Like others have mentioned, shoe adjustment and push rod adjustment will make a big difference.


Regarding "pedal ratio and is 5:1. Heard that it should be 6:1" will affect the foot force you need to brake but not the stroke to actuate the brakes, i.e., the 3" you have.
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Old 07-14-2020, 02:49 PM   #13
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Default Re: 40`Ford Brakes Update from 7/10 post

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Hi Farmerdick,
Regarding "pedal ratio and is 5:1. Heard that it should be 6:1" will affect the foot force you need to brake but not the stroke to actuate the brakes, i.e., the 3" you have.
Actually, I believe the ratio DOES affect the stroke. Imagine these two scenarios, exaggerated for clarity!

Pedal #1 is 12" long between pivot point and foot pad. It has a pushrod hole 6" from the pivot point....1/2-way between the pivot point and the foot pad. That would be a 2:1 ratio. If you push the pedal pad 4", the rod will stroke 2".

Pedal #2 is also 12" long between pivot point and foot pad. It has a pushrod hole 3" from pivot point. That equates to a 4:1 ratio. If we push the pedal pad the same 4", the rod will only stroke 1".
DD
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Old 07-14-2020, 03:40 PM   #14
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Default Re: 40`Ford Brakes Update from 7/10 post

Yes DD, whether the foot lever to actuating arm ratio is 4, 5 or 6 to 1 etc,, it needs to be sufficient to develop a full stroke of the master cylinder. Bigger number here reduces foot force for the same brake line pressure.



The problem that farmerdick has is 3" to 4" of "slop" without a firm pedal. This is caused by too small a master cylinder bore, too much gap between the shoes and the drums or a brake rod to master cylinder being too short, with lost motion until the MS starts it's stroke.


Glenn
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Old 07-14-2020, 05:04 PM   #15
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Default Re: 40`Ford Brakes Update from 7/10 post

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Originally Posted by glennpm View Post
Yes DD, whether the foot lever to actuating arm ratio is 4, 5 or 6 to 1 etc,, it needs to be sufficient to develop a full stroke of the master cylinder. Bigger number here reduces foot force for the same brake line pressure.



The problem that farmerdick has is 3" to 4" of "slop" without a firm pedal. This is caused by too small a master cylinder bore, too much gap between the shoes and the drums or a brake rod to master cylinder being too short, with lost motion until the MS starts it's stroke.


Glenn

I can surely agree with all of that! DD
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Old 07-14-2020, 08:37 PM   #16
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Default Re: 40`Ford Brakes Update from 7/10 post

Adjust all the shoes tight to the drums and then see what you have as far as pedal travel and hardness. If it is spongy you still may have air in the system? You may want to bleed it with the drums still tight. I always use a pressure bleeder to get air out but still have to have a second person ( Wife ) and pump slowly and bleed to get the remaining air out. The best thing without a doubt is have the shoes ground to match drums. Also make sure shoe material is not so hard that you can not push your thumb nail in the edge of the shoe. I have found store bought shoes are too hard and do not have enough friction. I also draw X,s on the shoe face's to see how much contact you have the next time you remove the drums. I use an old fashion brake shop here in town and have them relined and ground. Casper Brake K.C. MO.
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Old 07-15-2020, 07:27 AM   #17
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Default Re: 40`Ford Brakes Update from 7/10 post

Have you contacted Bert's in Denver as I suggested on the HAMB?? They now handle the Cling's adapter I believe.
Paul in CT
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