What is considered the Proper Brake adjustments

[Fullraceflathead]

I have read where the Model A brakes are to be adjusted so the rear brakes start to drag first at 1" of pedal travel then the fronts come in after another inch of travel. The idea back in the day was to have the rear brakes come on before the fronts. Is this Theory in braking still apply???
The front brakes work harder when trying to stop a vehical.
It would seem to me that the old theory could be OK but re-adjusting the brakes so the fronts take hold a little sooner than the rears would be much more effective based on today's technology.
What are the Majority of Mechanical Brake Model A owners doing???
Any input on this would be greatly appreciated as I'm about to adjust the brakes on my 1928 Roadster Pickup.

[rons49]

Boy here it comes! I used to try to conform to the original advise it the service manuals. One of the reasons that anti-lock brakes are installed on cars is to prohibit the rear brakes from locking up, and causing the car to skid left or right. If the Model A rear brakes are tighter then the fronts, I believe a skid is more likely. Engineers in the 1920s were a bit suspicious of 4 wheel brakes so they favored the tried and true rear stopping tradition. I adjust them the same, but that's me. Never an issue, or locked up rear brakes.

[newshirt]

This old thread helped me understand the issue a little.

http://www.fordbarn.com/forum/showth...3519&showall=1

[BRENT in 10-uh-C]

I personally feel that your answer lies in how does the Driver operate the vehicle? If a Model-A is set-up according to the Service Bulletins, --then operated in a manner in which it was originally intended, I think the old theory still applies. We are fastly approaching a society that does not understand how to operate a non antilock brake equipped vehicle in low-traction situations. In that scenario, they probably need more front brake bias simply because they drive their Model-A more aggressively.

[Fullraceflathead]

It seems I just opened a "Can of Worms"
Considering that the rear levers have more leverage than the front I think I'll try to make all four wheels brake the same and let the added leverage of the rear take care of itself.
It does seem to me that the 1928 thinking was rear brakes were more important than the fronts. Ford would not have changed the 40/60 braking ratio in 1932 to 50/50 unless the slowly began to realize how important the front brakes are in a panic stop.
My 1928 Roadster Pickup is the lightest of the Model A's at 2073lbs so I'm sure the back will lock up ans spin the truck if not careful in a panic stop situation.

[dave in australia]

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The idea of the backs applying before the fronts still applies today. The backs start first, setting the balance of the car. When the fronts start to apply, they come on quicker, so eventually do more braking. I'm not sure if the fronts apply quicker in the A, but the original front brake cams do not have a straight ramp, but a contoured one, so this may also be how it is for them. But, if you follow the SB's in adjusting brakes, and there is no concernable wear in the system, your brakes will be very good for a car with 4 1/2" tyres.

[BILL WILLIAMSON]

Well, just assemble your brakes carefully & properly, then adjust them to suit yourselves. That's what everyone's gonna' do, anyhow! Most folks NEVER change their ways, we ARE what we ARE!---- AND, we're always lookin' for folks that agree with our THINKIN'!! I jist hope everybody gits STOPPED, SAFELY!
Bill W.

[Jim/GA]

I studied automotive engineering at the Univ. of Michigan (in Ann Arbor, ~1 hour outside Detroit) in the late-70s, and even then (50 years after the Model A) there was debate about which wheels, front or back, should get more braking force. I designed numerous brake systems for various vehicle types. There is no right answer. Each has its pluses and minuses. Disk brakes, instead of drum/drum, are even more complex.

Skidding front wheels provide no steering to allow you to avoid obstacles or follow a road that is curving. Yikes! But pumping the brakes gives you intermittent steering between braking actions.

Skidding rear wheels allow the back end of the car to pivot around the braking front wheels. A classic spin out, but you can steer the car, and sometimes steer out of the spin. (BTW, this is Ford's design on the Model A.)

Wheel skid changes with weight on each axle. A pickup truck is the hardest to design for. Unloaded, the rears will skid first (quite easily, actually). Loaded, the front will skid first.

ABS on modern vehicles has really helped with this problem.

I tend to adjust the A brakes with a front axle bias, because the brakes are more efficient when setup that way, but I am well aware that I am fighting Henry's original design with the different lever arm lengths front and back.

[BILL WILLIAMSON]

Very GOOD post, Jim Cannon!
Bill W.

[harleytoprock]

If front and rear brakes had the same clamping force, the rears would skid first. Lost traction does not mean that your slowing down at a quicker rate. Skidding is not good. The rears would skid first because the rear of the vehicle is lighter and also because the mass of the de-acellerating vehicle is shifting to the front. Because of the front shift, the weighted traction on the front wheels increases. I think this is what modern auto engineers have learned. The modern invention proportion valve on late hydraulic cars creates more stopping force on the front wheels. Even before disc brakes, front drums were larger than rears. Motorcycles have dual disc brakes on the front but single on the rear. So it appears that engineers have learned that stopping power to come from the front is best. If Henry were still alive, he would have learned much by today and would have many design changes. I vote for 60/40 front to back. It's the modern way. Just my 2 cents.

[Y-Blockhead]

I am certainly no expert but the way the books say to adjust the brakes just doesn't make sense to me, adjusting the brakes so the rears skidded first. Once the rears start skidding you lose all rear braking power.

My way of looking at it is you don't want to skid any of the wheels, just stop in a controlled fashion.

I agree with the thoughts of adjusting with a little bias toward the front brakes and that's the way I adjusted them. I feel they stop much better now.

The example of the M/C is correct. Look at the braking area of motorcycle front brake rotors (2 large discs in front) compared to the rear (1 small disc in rear).

[Ted Duke]

Originally Posted by BILL WILLIAMSON

Well, just assemble your brakes carefully & properly, then adjust them to suit yourselves. That's what everyone's gonna' do, anyhow! Most folks NEVER change their ways, we ARE what we ARE!---- AND, we're always lookin' for folks that agree with our THINKIN'!! I jist hope everybody gits STOPPED, SAFELY!
Bill W.

Words of WISDOM!

Ted

[ericr]

Originally Posted by Jim/TX/GA

I studied automotive engineering at the Univ. of Michigan (in Ann Arbor, ~1 hour outside Detroit) in the late-70s, and even then (50 years after the Model A) there was debate about which wheels, front or back, should get more braking force. I designed numerous brake systems for various vehicle types. There is no right answer. Each has its pluses and minuses. Disk brakes, instead of drum/drum, are even more complex.

Skidding front wheels provide no steering to allow you to avoid obstacles or follow a road that is curving. Yikes! But pumping the brakes gives you intermittent steering between braking actions.

Skidding rear wheels allow the back end of the car to pivot around the braking front wheels. A classic spin out, but you can steer the car, and sometimes steer out of the spin. (BTW, this is Ford's design on the Model A.)

Wheel skid changes with weight on each axle. A pickup truck is the hardest to design for. Unloaded, the rears will skid first (quite easily, actually). Loaded, the front will skid first.

ABS on modern vehicles has really helped with this problem.

I tend to adjust the A brakes with a front axle bias, because the brakes are more efficient when setup that way, but I am well aware that I am fighting Henry's original design with the different lever arm lengths front and back.

BTW, do you find the entire front brake design on the Model "A" to be rather odd, with the actuating lever pushing on a rod pushing on a wedge after that? it almost sounds like a specific plan to reduce front braking efficiency.

I'd like to know what competitive makes (Chevrolet, Plymouth, Dodge Brothers, etc.) offered in terms of mechanical brake design....I suspect cables but I don't know for sure.

[rons49]

No Chrysler product ever had mechanical brakes... always hydraulic. Only the last year of Maxwell, then owned by WPC were not hydraulic. Chevy went to hydraulic in 1936, before 1936 they were cable mechanical.

[DougVieyra]

"WPC" = Walter P. Chrysler"

The brakes on my 1932 Pontiac were mechanical brakes of the cable type, which was the more common way, verses the rod (Ford) type.

- Doug Vieyra

[BILL WILLIAMSON]

I knew of a '32 Roadster that supposedly had the entire, cable operated system, from a '37 Lincoln Zephyr??
Bill W.