M38 Brake shoe Adjustment

ChuckW · Post by **ChuckW** » Tue Dec 17, 2019 10:21 am

On my 1952 M38, I have found that the brake shoes will not rotate on the bottom anchor pin eccentric when the nut is tightened. It's like the anchor pin tightens down on the shoe web before the brass eccentric cam, like the web of the brake shoe is thicker than the cam. I think I am correct in thinking that the shoes must be able to rotate on the cam in order to expand and contract against the drum. My thought is to lightly grind the web of the brake shoe until I get enough clearance for it to rotate on the cam. Anybody else had this problem? It appears to be only the front shoes, the rears seem to rotate freely with the bottom anchor pins nuts tight. These shoes were installed several years ago but have never seemed to work very well. The linings look like new on all 4 wheels!

Post by **wesk** » Tue Dec 17, 2019 12:05 pm

Chuck, can you confirm completely stock M38 front brakes and back plates?

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Incorrect dimensions on any of the Yellow Circled items in the next photo can cause either excessive tightness or slop to the lower shoe pivots. Those shoes should easily flop outward (fwd/aft) when the spring at the top is disconnected.

I would confirm the correct parts first. Then look at the linings, are they wider then the shoes? Any metal I decided to remove would be done in a way that the item remains centered or in it's correct relative position.

ChuckW · Post by **ChuckW** » Tue Dec 17, 2019 2:36 pm

Those shoes should easily flop outward (fwd/aft) when the spring at the top is disconnected.

That's what I thought. The shoes are aftermarket, so I suspect they are the problem. I don't remember where I got them. I am going to pull the shoes off and measure the thickness of the web and compare to the thickness of the eccentric washer.

ChuckW · Post by **ChuckW** » Tue Dec 17, 2019 5:26 pm

After a closer inspection, the shoes are definitely the problem. Rather than try to make them work, I think I will order new shoes all the way around. There is no telling where these shoes came from, I didn't keep any records back then!

Post by **wesk** » Tue Dec 17, 2019 11:33 pm

It will not always be the thickness of the web under the retaining plate (Item S) that will cause the binding. The width across the face of the shoe can also cause the binding if when the shoe inboard edge lies against the backing plate the web area of the shoe does not rest against the plate's mounting surfaces. The shoe's web should should just touch the mounting surface of the plate "S".

Jeff_Lee · Post by **Jeff_Lee** » Fri Dec 20, 2019 4:19 pm

Also check and make sure your eccentric (the little brass cam - part L in the drawing) doesn't bind in the hole in the shoe. They need to be a tight fit, but MUST rotate to adjust the shoe.

I recently bought some aftermarket eccentrics and they were slightly larger than the holes in the OEM Bendix shoes, which I had relined. The eccentrics I removed were a perfect fit. I suspect the newer parts were offshore parts that were slightly over tolerance.

ChuckW · Post by **ChuckW** » Sat Dec 21, 2019 4:04 pm

New shoes came today. The web on the new shoes is a good .012" thinner than the old ones and the shoes will swing free with the bottom adjusting stud nuts tight now.
The lesson I learned, from now on, I will always measure the thickness of the brake shoe web and the thickness of the cam washer! Of course, at my age, this will probably be the last M38 brake job I ever do! Maybe it will help someone else!~