Why were the rear brake shoe linings shorter on Lockheed brakes?

[MarcDeSoto]

Does anyone know why the two rear brake shoe linings were originally only about 9", while the other shoe linings are 11 to 12" on a 48 DeSoto and other Mopars?  Bernbaums told me the short shoe linings are no longer made, so why were the rear shoes made shorter in the first place?  And will putting in the long shoe linings in the rear affect my braking somehow?  Thanks.  

[desoto1939]

Here is you explanation.

 

Since you have a single wheel cylinder on the rear and these with have step piston or two different sizes the lockeed brake shoes were designed and engineered so that the short lining alwasy goes to the back of each shoe and the short lining was at the bottom of the shoe.

 

 

When the Bendix type brakes were used these were a floating style brake and not supported by an eccentric pin like the Lockeed. The Bendix were insatlled with the short shoe up front and the long lining on the rears.

 

In my 1939 desoto manual it shows that the shoes are installed with the short on the rears and the lining is at the bottom of the shoe.  This is factory correct.

 

Hope this explains the reasoning.

 

Rich Hartung

Desoto1939@aol.com

[keithb7]

As a general rule, much more braking force is performed by the leading brake shoe, compared to the tailing brake shoe. Larger brake surface area on the front, means better braking performance.  More friction area. Front brakes seemed to always get the R&D money. Even today there are still new vehicles made with front disc brakes, and rear drum brakes. The front does all the work! Except when backing up. Yet how often and how fast are we going in reverse compared to forward?

[JerseyHarold]

Way-back-when in engineering school I remember being taught that the front ('lead') shoe on a drum brake is self-energizing.  The shoe is pulled tighter by the rotation of the drum and thus gives more effective stopping power.  The trailing shoe acts to reduce the stopping power of a drum brake (in a sense repelling the drum).  The trailing shoes have shorter linings so there is less contact between the undesirable portion of the lining and the drum.

 

If someone can offer a more descriptive explanation please do.  The last time I thought about this stuff was when Nixon was President!

[MarcDeSoto]

But on the post war Lockheed brakes the brake shoe linings are both 11.5" on the front axle and on the rear axle the front shoe is 11.5 and the rear shoe is just under 9".  All I want to know is it ok to put 11.5" shoes on the rear axle front and back.  I continued to learn how to use the Miller 19 tool today.  It took some experimentation as the parts can go together is several ways.  With the help of Rick, I finally got it figured out, I think.  I put the 41 sleeve on the rear axle and the 70 sleeve on the front axle.  And I used the pin to determine the inside diameter of the drums.  Thanks, Marc.

 

[allbizz49]

Using equal length shoes on the rear is fine. 

[Sniper]

11 hours ago, JerseyHarold said:

Way-back-when in engineering school I remember being taught that the front ('lead') shoe on a drum brake is self-energizing.  The shoe is pulled tighter by the rotation of the drum and thus gives more effective stopping power.  The trailing shoe acts to reduce the stopping power of a drum brake (in a sense repelling the drum).  The trailing shoes have shorter linings so there is less contact between the undesirable portion of the lining and the drum.

 

If someone can offer a more descriptive explanation please do.  The last time I thought about this stuff was when Nixon was President!

This is true on modern self energizing brakes, which we do not have.  If one end of the shoe is permanent held in place it's not self energizing.

 

Here's a video from Speedway showing the difference, it uses Ford stuff as the example but it's applicable to us.