'40 brake shoe position

[40cpe]

I'm replacing the king pins/bushings in the '38. I bought the car with the '40 hydraulic brakes on it. When I disassembled the brakes I was pleasantly surprised to find a really neat and clean installation with new shoes and smooth drum surfaces, clean bearing grease. BUT, the short shoe is on the front. The brakes stop as well as you could expect them to, no pulling, etc. I'm kind of "if it ain't broke, don't fix it" kind of guy. How much difference does it make if the shoes are reversed? Has anyone experienced a night/day difference when reversing the shoe position?

[V8 Bob]

The brakes may not be "broke", but the assembly is not right. The forward longer lining does the most work on the Lockheed non-servo drum brake, so why would you want to minimize available braking .

[19Fordy]

1940 Ford brakes are Lockheed style brakes. It is correct for the large shoe to go on the front (facing forward) and the small er shoe to go on the back (facing rearward). Photos show left front and left rear. The later style Bendix brakes have the long to the rear and the shot shoe to the front because Bendix brakes are self-energizing. Your brakes are already installed correctly. Much info. on how to adjust them and the parking brake is on the Fordarn. To have it at your fingertips buy the book shown.

[tubman]

These guys are right of course. However, when I was a kid, I didn't realize there was a difference in the brake shoes and put 'em in in the order they came out of the box. Never noticed a difference on any of those cars. Now that it's apart, you should fix it. If it weren't apart, you probably shouldn't bother. That being said, if it was still together, you wouldn't have known it was wrong.

[40cpe]

You guys are right, the reasonable thing to do is to correct them now. Thing is, they work good now, maybe not when I get finished "fixing" them.

[19Fordy]

Sponsored Links (Register now to hide all advertisements)

40cpe: Here's a helpful video.
https://www.youtube.com/watch?v=rD-Wk2heBH8
This explains how Bendix and Lockheed brakes work and why Bendix is better.
Read it all and you will want to switch your brakes.
https://www.fordbarn.com/forum/showt...5506&showall=1

[40cpe]

I hear you. No argument from me.

[Mart]

Check the wheel cylinders have the larger end to the front. The front ones obviously go this way due to the hose angle, but the rears are often fitted large end to the rear as the pipe run actually seems more logical that way.

Mart.

[drolston]

The physics involved supports the observation that you can not tell the difference in braking between having the linings in the right way or reversed. The drag force of the shoe is the coefficient of friction times the wheel cylinder force applied, regardless of the area over which that force is spread.

The rear shoe gets the bigger force because of the larger wheel cylinder diameter in that direction. Maybe they used a bigger lining so that the pressure (force/area) would be more equal between front and rear shoe. That would tend to equalize the rate of wear of the linings.

[V8 Bob]

Originally Posted by drolston

The physics involved supports the observation that you can not tell the difference in braking between having the linings in the right way or reversed. The drag force of the shoe is the coefficient of friction times the wheel cylinder force applied, regardless of the area over which that force is spread.

The rear shoe gets the bigger force because of the larger wheel cylinder diameter in that direction. Maybe they used a bigger lining so that the pressure (force/area) would be more equal between front and rear shoe. That would tend to equalize the rate of wear of the linings.

The non-servo Lockheed wheel cylinder's larger piston faces towards the front, not the rear, along with the longer lining.
Running the shorter lining forward will result in higher wear and increased fade during hard braking.

[drolston]

Originally Posted by V8 Bob

The non-servo Lockheed wheel cylinder's larger piston faces towards the front, not the rear, along with the longer lining.
Running the shorter lining forward will result in higher wear and increased fade during hard braking.

Yup, - kinda said that backwards, but the principle still applies. More force on the bigger lining tends to equalize pressure and wear.

[V8 Bob]

The Lockheed's longer front lining and larger wheel cylinder does most of the forward braking, by design. Incorrect assembly makes this non-servo design even more inefficient than it already is, compared to a servo design. No good reason not to assemble correctly.