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Secondary brake spring on some 30s and 40s cars.


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Hello AACA Technical Folks:

I'm working on the brakes of a 1937 Pontiac ... rebuilding wheel cylinders, replacing springs, and flexlines, etc.

These brakes seem to use an "extra" spring (well, extra compared to what I think of a normal hydraulic brake system).

I think that this spring is called a secondary spring that attaches between the center of the secondary (rear) shoe and a post

that extends outward from the backing plate. It appears as if this spring trys to pull the secondary shoe forward (towards the

axle) and holds it firmly against the rear eccentric when the brake is released.

Note: this spring is in addtion to the normal springs: the two upper springs that hold each shoe against the anchor post, the bottom

spring that pulls the shoes against the star adjuster, and the backing plate springs that hold each shoe against the backing plate.

My master parts book shows that this spring is part number 1415663 and was used on 37-38 and 42-48 Pontiacs. I'm guessing that

a similar spring may have been used on some other 30s and 40s cars.

Someone working on this car in the past (it has been garaged and not driven since 1968) apparently decided that these springs were

not needed and removed them. Also, the spring hardware kits that I purchased (supposedly for a 37/38 Pontiac) included all of the

"normal" springs, but not these.

So, I have 2 questions:

1. Does anyone know where to purchase replacement secondary brake springs for this application?

2. Was there a subtle design change over the years that made these springs expendable or were they generally

found to be either redundant or ineffective?

Thanks for you help,

John Shott

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Sounds like this additional spring on the rear shoe was intended to cause the primary shoe to contact the forward-rotating drum first, thus adding to the "self-energizing" effect?

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