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Everything I ever worked on that had shoes you put the shorter toward the front and longer toward the back. The ones I have taken off this jeep are that way too. When I bought my shoes on KW(I usually read all the questions and answers), the guy answering said the long shoe goes in front. Which is it, and for the record I doubt if it makes much difference.
The froward shoe is longer on some drum brakes. The theory is three fold. Initially the belief was the drum clearance collapsing under the force of the stopping vehicle, would aid in stopping power. Latter it was thought that the added stopping pressure required less shoe up front and more in the back. Then there is the thought that rotation added pressure. So 1940's thought process vs 1960's thought process. I think it's called "Six to one, a half dozen to the other". My 1950 had the long shoe to the front. The Universal Service Manual is of little help as to when or why. It simply states "NOTE: On some vehicles the lining on the front shoe is longer than the lining on the rear shoe".
This is a great debate question. The early 57' Chevy manual photograph shows clearly the long shoe in the front. The early Ford manuals show the long shoe to the front. The 1965 Chevy service Manual shows the long shoe to the rear, as does the 65' Ford. The Jeep Manuals are vague. There are theories of axle rotational forces. I am certain in the modern era of DRUM brakes, everyone evidentially decided on B.O.B. Big shoe On Back. A little ditty from an automotive class.
I also wondered if they changed that theory around the time of self adjusting brakes.
Yes, right around the time of self adjusters.
Google search regarding proper orientation of mismatched brake shoe configurations seems to indicate the small shoe should be mounted on the front while the larger one is to the rear. When I diassembled / removed the rear drum on this Jeep, the large shoe was towards the front / small towards the rear. I noticed the wear characteristics were very disproportional as the big shoe had much more friction material remaining while the small shoe is extremely thin. Which is why I questioned if the previous mechanic installed the shoes incorrectly. I'm going to reassemble with small shoe forward.
There are a few different types of drum brakes that were and are used on automobiles. Here are some. Simplex, Duplex, Uni-servo, Duo-servo, and Duo-Duplex. There are even a few other modifications of these. In general the force generated changes somewhat depending on the design. The attached illustration from Wikipedia shows how the force relates to the design. The distribution of the force is highlighted in black. So the design matters but, which shoe goes where is still up to how you want the brake to behave. If the long shoe is placed in a high force area for the design you have, the brakes will be more aggressive than if the shoes are reversed. Will you feel the difference, I don't think so. It could effect the wear. You would want the "most shoe" in the high force area for the best length of wear.
https://en.wikipedia.org/wiki/Drum_brake
When I did brakes on Flossy. The old shoes were larger towards the front/smaller towards the rear. The new shoes I got (raybestos brand) were all equal.
Have all of the brakes disassembled right now. Three wheels had large shoe towards the rear, one with large shoe towards front. Noticed in Kaiser Willys parts book it specifically states that large shoe goes towards the front. Brake system will be 100% new other than the drums when complete. Including new dual res master and all new lines [hard and soft]. I'll tackle the parking brake later.
Catlewis:
You are indeed a wise man to put so much effort into brakes. Some guys let brakes be an afterthought and their biggest effort is to just get a Jeep running.
Getting it to stop is as critical as getting it running. There was a TV commercial a year or so ago that had the tag line; "Well, something will stop it" - not a good approach to Jeeps.
Take a hard look at your drums. On the '48 the drums were right at the reject limit, so we used new drums. Then about a year later, (not that many miles) the brakes got a bit wonky. They surged and had a screech and shudder as the truck came to a complete stop. It turned out that even the new drums were out of round - so look them over carefully. Even if they are not too worn, check for concentricity.
Take care and keep us informed on the project - it's looking good,'
Cat, where did you see that reference for the big shoe to the front? That is interesting because you have a '65. That should be a Duo-Servo design in 65'. The largest force would be to the rear. In that design for best wear the large shoe should go to the rear and the small shoe should go to the front. Usually the long shoe goes to the front in the older Simplex design like the Early MB's and CJ's. Once again however, it depends on how you want the brakes to behave.
This is interesting because it would indicate in the 65' they were more interested in stopping power over wear. This would explain somewhat why in the Universal Manual, it indicates they can go either way. It must come down to individual mechanical preference of the installing mechanic. In any event they must all be installed the same way on each wheel in the front and the rear, left to right.
It's on page 106 in the 2023 catalog. It's located in the lower right corner of the parts illustrations [which are located at the top of page] near the binding. "TIP: BRAKE SHOES" The primary shoe has the longer padding and is the one that goes in the front.Quote:
Originally Posted by bmorgil
Also per the illustrations you provided previously I would guess this braking system is "Simplex". Single wheel cylinder, with one hold down pin per shoe and adjuster at the bottom.
That would do it Cat. The Simplex would have the big shoe to the front for best wear.