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I am installing restored brake drums on my 1930 Model A. Three install fine, but the fourth doesn’t. I have made all the adjustments for bendix 3-shoe brakes as described in PASB 1974-5, but the result is still that the linings are too thick or the drum is too small. I can force the drum on over the linings, but then it can only be turned with a four foot lever. When I take it off there are shiny spots on the linings. The shoes and the drum did not come off the same wheel originally.
The linings are all between 5 and 6 32nds inch thick, so I have plenty of lining. I think I only need a little clearance — perhaps 0.015 to 0.020. I don’t like to take anything off the lnings — messy, dangerous, and shortens their life. I am thinking of having the drum turned to take off a little metal. The drums have probably never been turned.
I would appreciate advice and suggstions.
THanks.
The metal if removed from the drum can never be replaced. The lining however can be. Call around for a good brake shop that does truck brakes. they will have a shoe-arcing grinder.
Can you measure your other drums, maybe this small inside diameter drum will fit on a different axle, with different brake shoes..
Are the shiny spots on the shoes even all over the lining, or only on the center or only on the ends of the lining ?? Unless the shiny spots are even across the entire lining, then the shoes need to be matched to the drum anyway.
Make sure your brake activating cam is in a position to not move the shoes outward at all. Make sure the shoes are properly seated against the cam, and shoe anchors.
You could instead of grinding the lining, take a few thousanths off the shoe anchors, unless these shoes have a round pin for each end..
I’d get the shoes arced, do some accurate measurments on the drum inside diameter and the shoe diameter, I’ll bet that only a very little needs to be taken off the lining.. and let a shop with the correct machine do the job..
Are all the other shoes matching the drum with even touch-marks?? if the shoes are not matched, to the drum you will have spongy and ineffective brakes..
Greg Long
When doing a brake job there are two procedures that should be included in the work. First, have the drums trued to assure that they are round. Second, have the shoes with the new lining arced to the individual drum with which they will be installed. These two procedures will give the best possible contact between drum and lining for the most effective braking. Almost any brake shop that’s been around for a while should have the equipment to do this work.
Recently I was installing the brakes drums, on a ’31 series 42, after cleaning up the brake shoes and had a similar problem. I found it was due to the anchor pin position. By loosening the nuts and tapping with a hammer I was able to center the shoe assembly and then easily install the drum.
Al
Pierce brake drums of that period can’t be “turned” on a lathe with a cutting tool, they must be ground….they are made of some special steel….if you lay one on the floor, drum opening up, and tap with a wrench, it’s the prettiest bell sound you can hear….
I agree I’d change linings before I’d remove metal….
You’re right. The brake drums are cast steel. This requires drum truing equipment with the capability to grind the drum surface instead of cut it. The drum truing equipment in most older shops should be able to handle this.
Many thanks to all for the helpful responses. I am a lot wiser.
I will consult the local truck shop again, and ask their help on fitting the linings. I took them a pair of front drums and just asked them to turn them, and they did a good job. They obviously knew how to do it with the right equipment. it turned out that these two drums were pretty deeply pitted. I had another better pair which I cleaned up and used. Davit is right — they ring very nicely!