Just trying to confirm what I think is the correct way to install the brake shoes on my 61. The rear shoes appear to be the same size (a box of 4 identical shoes); the fronts have a long and a short size. I seem to remember the long shoe going toward the back to provide more stopping power when applied with the weight of the car wanting to keep going forward (physics). But when I look through the old Chiltons Unit Repair section, it lables the front shoe as primary, and seems to show the back shoe longer??? Any thoughts? Thanks!!! Jim
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Re: C1 - Brake Shoe Orientation
Jim,
The Chilton manual is correct. The long shoe is installed in the rear position. Since the wheel/hub are fixed to a center position, (spindle) there really is no front or rear force applied inside the drum. The forward energy is absorbed into the spindle, not the brake drum or shoes.
Now for the big question. Who can tell us the actual purpose of a long/short shoe arrangement.
And why is the brake shoe spring rate different between front and rear shoes. -
Re: C1 - Brake Shoe Orientation
The front shoe is the primary and is shorter than the secondary rear shoe which is longer on a self-energizing system like your Corvette. I think your linings should be 2 inches wide but I'm not sure.Comment
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In a self-energizing system, the front shoe tries
to bite into the drum. This forces the shoe to push downward and since there is no anchor at the bottom of the shoe, that force is directed against the bottom of the rear shoe as the top of the rear shoe is being forced against the drum by the wheel cylinder. So, basically, your front shoe contacts mostly at the top of the shoe and not much at the bottom. The rear shoe on the other hand is full contact by means of what I described.
The Chrysler center plane dual wheel cylinder brakes of the '50's used equal length shoes I suspect since they had equal forces against each shoe. Two cylinders and two anchor pins.Comment
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Re: C1 - Brake Shoe Orientation
Your old Chiltons is on the money; front shoe is primary AND has the shorter lining. Drum brakes are self energizing, meaning the some of the frictional force reacts to make the shoes press even tighter. Making the forward shoe shorter helps minimize the effect so you don't lock up at every stop sign.
I would have thought my '63 rears, being the same basic size, would have the same shoes. Parts book says otherwise. Pictures still show shorter primary shoe so I wonder about what came in your box. Stand by for C-1 experts.Comment
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Re: C1 - Brake Shoe Orientation
Thye short shoe should grab better in the forward rotation and throw the rear shoe against the drum...I think As for the springs does that have anything to do with the self adjusters?Comment
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Re: C1 - Brake Shoe Orientation
Different return spring rates? Never thought about it before but my guess is you want the front brakes to actuate first on application and de-actuate second when you come out of them.Comment
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Re: C1 - Brake Shoe Orientation
Ok, that's half of it Chris. The front/primary shoe, by design, makes contact with the drum first because the primary return spring is weaker than the rear/secondary spring. When the vehicle is moving forward and the brakes are applied, the primary shoe extends and contacts the drum. As contact is made, the rotational force of the drum tries to rotate both pri and sec shoes along with it but the top of the rear shoe is against it's stop, or pin, which prevents the motion of the shoes. This eliminates the "clunk" of the shoe hitting the pin that you would hear on brake application in a forward direction if the rear shoe was off it's seat. That would be the same noise, or "clunk" that you do hear when you apply the brakes while moving in reverse. In reverse, the pri shoe leaves it's pin and makes contact with the drum but now the rotational force is in the opposite direction which moves the front/primary shoe back against the pin, causing an undesireable noise.Comment
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Guess #2
Or.....
To get them to actuate at the same time. With different dia. wheel cylinders front to back you have different forces to balance.Comment
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Re: Guess #2
Chris,
I should have used the words primary/secondary instead of front and rear. I was refering to the shoes for one wheel. The return spring for the primary shoe is of a different tension than the spring for the secondary shoe.Comment
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Re: C1 - Brake Shoe Orientation
Well, I read that one wrong.
Thought you meant front and rear axles, not front and rear springs of a single brake assembly. Would still have been guessing. Certainly appreciate the education.
Back to Jim's box of C-1 rear shoes. No way there should be four identical shoes for the rear axle is there?Comment
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Maybe Roy Braatz Can Help With This One....
Chris,
I tried to find some info on C1 brake lining but I don't have anything that will help on the length of lining. As far as I know, and that's very limited for C1, the lining sets had a pri and sec shoe but that's just a guess. It's possible that early/mid 50's Chev pass cars had equal length pri and sec lining?Comment
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Thanks everyone!!! *NM*
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