# Thread: Brake Shoe Question

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## Brake Shoe Question

I think I know the answer but I just want to be sure.

On my 1950 Buick there should be 2 different size shoes on each cylinder right? The pad with the longer deposit of brake material should go toward the front of the car (primary shoe) the one with the shorter deposit should go toward the back.

The guy that had my car before me must have assembled it in the dark because no one wheel cylinder seemed to be the same as another so I really don't have anything to go off of and the manual really doesn't come out and say it.

Thank you,

Lee

2. Close, the primary is the short pad and goes to the front. You can see them installed all kinds of ways!

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I'm going to throw a bit of physics in here just for fun. Brakes work because (obviously) of friction. Different material combinations have different coefficients of friction which is another way of saying that some combinations work better than others. Here's the interesting part. The coefficient of friction is the same between a given combination of materials REGARDLESS OF THE SURFACE AREA INVOLVED! What that means is that if you have a set of brakes with, say, 4 square inches it will act the same as 8 square inches, as far as stopping the car . . .up to a point. What changes with different areas in contact is the heat generated by the brakes. That's why larger brakes (as a general rule) stop better than smaller brakes; there is less heat buildup (which is the enemy of that coefficient of friction) therefore less brake fade, so you stop faster. Here's where I'm going with all this. It is my theory that, for all practical purposes, it really doesn't make a bit of difference whether you put the short shoe on the primary or secondary because, in the final analysis, any given wheel has a fixed amount of braking surface regardless of which shoe is where. I'm open to discussion, guys.

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Thank you for the replies Bob and njlimbaugh.

And yes, I saw them installed every single way you could on this car....

In going with njlimbaugh's theroy, I would think that the primary shoe would be the one with more braking material on it due to heat dissipation. But if the brakes shoes are applied equally I guess it doesnt matter what shoe is where.

But since I didn't design the car and dont want to be laughed at by other Buick people I'm going to go small shoe front, big shoe back.

Thanks again,

Lee

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## Brakes, Brakes !

Hi, This may be a little long and I am sorry.
I just went though this. and yes the longer one does go to the back of car. My brake shoes on the back right side of the car were put on with the shorter one on the back. This shoe was broke and wore funny. I was told that who ever put them on look at the right side to copy and got it backwards. This person said that the main braking is the back. They also said that they have seen where they will put the longer ones on the right side and the shorter on the other side. So we are the only ones that do not know. I have learn alot from having to do this and alot of that help came for here. I also had some one help me adjust the brakes and leard that when you adjust them you need to adjust them all the way out and then back it off to were you can turn the wheel and listen to the sound it makes. My back wheels. which are 66" wildcat sounded like they were even. The front 55" roadmaster sounded like they were skiping and not hitting even. This was because the drum was out of round. So I adjusted them out until until i could hear them hit all around. They still hit more in the spots that I heard earlier but you got make out by the sound that they were just hitting the rest off drum. I then was told to put car into nutural and then turn wheels again. The back right was a little tight, so was told to back off alittle. I was told that the reason you adjust them like this is to ( I can not remember what he called it) but it is so the the brakes wear to the drums. You drive it for a while like this to fit brakes to drum and then you readjust them again. but you adjust them all the way out and then back them off. Doing it like this to fitt bakes to shape of drums is so you get the pads to brake on all of drum. I was told that they use to do this in brake shops with a machine. Put no one really does it any more because all the new cars have disc brakes. What we have to do to have a classic car. Put I think it is worth it. I would never give up my classic car.

6. njlimbaugh,

That sounds interesting. You must have had an interesting career. I had to find out "why". While I am sure what you say is true, there is a good reason for the primary and secondary going where and how they do, (of course).

You will find it explained here:
http://www.carbibles.com/brake_bible.html
scroll a little ways down until your see the drum brakes.

Thanks for the Physics, a comment always make one think and learn!

7. ## brake shoes

the longer shoes in back of drums,shorter in front,the same front and rear.
Charlene has made it all right in her car.Adjust ancor bolt,and adjust the
crone to max of pads/drums not so its stucks.
Stubbe.

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## drum brakes

there is also a type of drum brake which uses the self energizing principal with "only a single piston". Pressure from the cylinder wedges the primary front, [small] shoe into the secondary rear, [larger] shoe thus wedging it into the anchor bolt behind the cylinder. The large secondary shoe, due to the combined pressure and more friction area provides added stopping power in a chain reaction. Heat plays a big role in drum brakes, I have found that riveted shoes dont seem to fade as much, also there have been some success with drilling small holes in the drum contact area to relieve heat and any gassing from the shoes. see below.

http://www.chtopping.com/classictruck.html
Last edited by 39CENT; 08-01-2009 at 11:55 PM.

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my method of adjusting drum brakes is to get the shoes to were they are just touching the drums. then I test by pushing on the pedal to set the shoes. Then I go back and tighten each brake adjuster till shoes are tight against the drum, and the drum is locked, then loosen to a small drag on each drum. Have someone test the brakes by pressing the pedal. Now you can get on the road and try stopping a few times, go slow in your neighborhood and see if they are responding before going into traffic not hard just to see if they pull or something. Then speed up and start trying them, then give them a few hard stops to see how the pedal feels. If everything is working ok you got it made.
Last edited by 39CENT; 08-01-2009 at 11:28 PM.

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## leading and trailing drum brake shoes

ok there is always a mix up about leading and trailing [primary and secondary] brake shoes. I finally found a web page that had a pic and instructions on which is the leading [short] shoe. Many articles were misleading and just plain wrong! below is a pic of a left rear drum brake assembly, the leading shoe is the left one in this pic and is visibly shorter, this is the common drum brake setup.

http://www.aplsweb.com/Topics/Rear-Brake-Assembly.jpg

It is important also to check your brake shoes if you see any oil or grease leaking from the backing plates, I have an opinion that if you have any brake fluid loss can cause the rear axle bearing seal to weep and then evnetually bearing failure, or vice versa a bad bearing can cause brake cylinders to fail, as many time I have seen both problems. also the wedging action with drum brakes along with oil leaks can cause brake lockup.[ I heard of a guy that flipped his Buick at the drags because of that]. I usually look at the pix in my Motors manual to make sure whats right, I have found many brake shoes installed wrong.
Last edited by 39CENT; 08-02-2009 at 12:14 AM.

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