Adjusting Brakes...Why Equal Temperature ?

Vic's explanation referencing the ratio of the front lever arm to the rear lever arm is correct. The 15 degree setting for the front lever provides a near optimal horizontal pull position which allows some tolerance for wear of the shoes and still maintains effective braking performance before making the next adjustment. The ideal orientation of the lever is vertically upward. When the front brake rod is activated in this position, the pulling force at the pin connection of the lever is totally horizontal (no vertical component). However, once the shoes begin to wear the horizontal pulling force at this setting begins to rapidly decrease.
The intent of the original design was to provide more mechanical advantage to the rear braking system as a means of preventing premature locking of the front wheels when driving on gravel roads. From what I have been told and read about, roads in the Model "A" period where mostly gravel. So this design concept for these types of road conditions makes sense.
Personally I try to adjust my brakes so they are as close to being equal as possible because we obviously no longer drive on gravel roads except when we encounter one while touring.
Jack in CT
 
marc, since acquiring mine in late march this year (late 31, restored in the 80's w/615 miles{orig u/known}). I haven't felt the need or opportunity to adj, but will use les's method i'm sure.
Paul in CT
 
I agree with the posts about NOT locking the rear brakes. I had mine set up in the standard way until a pedestrian stepped in front of me and there was a bicyclist on the right. Locked up the rears, steered right and prayed for the bicyclist. The car didnt slow much, but the rear screech sure alerted people and the bicyclist was alert and stopped in time. Since then I have been working out in a large parking lot to get the fronts to take a little more braking action without locking up and the rears to not lock up, because the rear skid provides no braking action at all (or very little.) You do not have 4 wheel brakes when 2 are skidding. This assumes that the mechanical parts, 15*, slop in the rod clevis's, wedges, etc, are correct. The adjusting board and now the new heat test may be good starting points, but the real test is actual operation. Make the finish adjustments with the brake adjusting wedge as necessary for each wheel. You can take up the angle differences that Vic measured by adjusting the wedge, looser in the rear. Get out in a parking lot and stand on the brakes to get them so that all make a smudge of rubber, not lock, at the same time. I think the idea of the rear locking first, or at all, needs some serious discussion. I for one do not think that locking the rears is the best arrangement for best braking. IMHO
 
The brake system on the A is 60% rear and 40% front.

After relining all shoes, arc a pair to each drum ( keep each pair associated with its drum); the purpose is because each drum when turned will no doubt measure differently.

I start at the brake pedal and adjust the rod to the brake cross shaft so the clevis ends are vertical on the cross shaft. I then attach the rear brake rods, pull out the slack that is built into the rear brake system, then adjust the rod so the pin slips into the brake cross shaft clevis, set jam nut on rod. Then move to the front brake rods; attach the eye to the brake cross shaft, pull the slack out of the front brake cross shaft lever, adjust rod so clevis pin slips in. set jam nut ( leave front brake rods not connected at this time). Adjust rear brakes shoes so they are lighty touching the drum. Drive A on a smooth level black top street at 10 MPH, jam on brakes and make emergency stop ( this will leave black skid marks on the street (the length of the marks should be equal and the car should not pull left or right) adjust rear brake shoes and continue testing until emergency stop skid marks are equal and car doesn't pull left or right . Now connect front brake rods, adjust shoes until they just touch the drum then back off 3 clicks. Make one more emergency stop to make sure car doesn't pull left or right, and adjust accordingly.

During the above tests, I am constantly touching the drums checking for excessive heat.

I use rivited woven lining, I myself prefer to not use bonded lining as its a harder lining; a softer lining with mechanical brakes seem to provide better brakes.

As Marco said: be sure to have your 15 degrees forward of center on your front cross shaft arm.

Once you have your brake cross shaft correct, your rods adjusted correctly, you shouldn't have to ever touch them again, only adjust shoes as they wear, and when you have no more adjustment its time for new shoes.

This method has worked good for me, probable others have just as good results doing there brakes a different way.

Ron
 
I ask again, can someone please tell me what the temperature should be on a pair of well adjusted brakes after a five mile drive of stop and go driving. The drums are cast rockie mountain type. Is it a question that can be answered? Thanks very much.
 
Frank, I have no idea what the teimp should be or even how it would be calculated. The drums are a big heat sink and there are ways to calculate heat dissipation for electronic systems, but beyond setting the home thermostat it is way over my head. Maybe a PhD in thermodynamics with a super computer could do it. Maybe you could measure a bunch of different cars and see what the numbers are.
 
Barners:
I have 6 cars with 4 currently roadworthy. It has been a few years since I have taken measurements and I have not kept records. You do not need to drive 5 miles to get good readings, a mile or so will do to get the drums up to normal operating temperature. First drive around and let the car come to an easy stop using the emergency brake. Get the car up to 40 MPH or so and come to a fast stop without locking the wheels. I recall that temperatures were 165 to 200 degrees after 1 stop. Subsequent stops brought the temperature up a little above 200 degrees. The brake drums will shed some heat in the few minutes that it takes to take and record the temperature. Driving a little will also cool the drums. Remember that the higher temperature will cool faster because of the heat transfer equation Q=U*A*delta T. I paint the drums with high temperature gloss black - good to 500 degrees F. I have never boiled the paint off the drums. I do not know what the "fade temperature" is. I suspect that it is different for all and it shoule be able to calculate it using the thermal expansion coefficient of the drum material. Comments are welcome.

Vic
 
Vic thanks for the information. When I have checked the temps on my brakes they have been in the same range that you're talking about.
 
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