Front Drum Brakes


#1

My 1963 Holden has drum brakes all round. The fronts had always been a problem pulling and shuddering. I have had the drums machined and fitted new shoes and adjusted them up correctly. The shoes are the correct fit in the machined drums.

They are now working really well when cold. Once they heat up I am getting a bit of shudder, nowhere as bad as before but still annoying. No longer pulling to any great extent. My question is, why would the shudder only happen after driving for a while and the brakes warm up?


Dave


#2

Loose backing plate, bad wheel bearings, worn idler arm, frozen slave cylinder, primary and secondary shoes in wrong location. Then there is something unbelievable that I haven’t encountered and hope you find.


#3

On drum brakes the lining material is much more important that on discs. The last family car I bought with drum brakes was a 61 Dodge Dart Phoenix with a 318. The brakes had been done at Sears just before I bought it and the must have bought the linings from Kleenex.At anything over 70 they would just shudder and smoke. You could not lock uo the wheels.

I went and bought a set of Grey Rock brake linings, a brand that was used in Nascar at the time and you could hit the brakes at any speed and just set the car right down. I don’t know if anyone makes high- performance brake shoes any more but you could probably get better than you have. We used to buy over sized shoes and have them arc-ground to fit the drums so they made full contact.


#4

Yes I am starting to wonder if its the quality of the linings. The brakes were fine for the first couple of weeks but started to shudder again when heated up a bit after this time. Maybe once they wear down a bit they are not working as well as they should?


#5

Once warm, your brake shoes no longer fit the drum as perfectly as they did when cold. This can cause shudder. This is ONE of the many reasons manufacturers no longer use front drum brakes. Changing lining material can help. Organic (asbestos) linings are best but I’d guess tough to find these days.


#6

If the front brakes use a single wheel cylinder there is a primary and secondary shoe and reversing their position, as mentioned above, will cause grabbing and possibly lock up. Also, beveling the leading edge of the brake shoes might help.

I corrected myself. It’s the leading edge of the shoes, especially the primary shoe that benefits from beveling. Way back when working on 4 wheel drum brakes I beveled both ends of both shoes. And I recall a crown grinding machine that radiused shoes to perfectly match the diameter of the drum after it was turned. Done correctly a brake job resulted in like new performance.


#7

All good ideas. I’d be suspicious of the quality of the shoe material, as mentioned above.

I’ll add this. I have drum brakes front side on my 70’s Ford truck and never had this exact problem, but when the brakes seem not to stop as well as before, esp when hot, I’ll take the drums off and sand them and the shoes with some AlO2 sandpaper, 120 grit, with the sanding direction 90 degrees to the stopping direction. Not much sanding required, just a little. The idea is to deglaze the surfaces and give the two surfaces some surface texture, something to bite into. Has helped to improve the braking performance for my truck at least.

Inexpensive. Doesn’t involve messing with the hydraulics. (As long as you don’t accidentally press on the brake pedal with the drum off … d’oh, I did this one time! ) Worth a try at least.


#8

Next time they start grabbing, jack the front of the car and see if the wheels spin freely. You are checking for brake drag causing overheating of the braking surfaces.


#9

@1963EJ…try this procedure. I know you said that you adjusted the brakes properly but you may be missing a step. I always tighten the brakes as tight as they will go and then back off the adjustment until the wheel will just turn easily. A loose brake adjustment can cause brake grabbing.


#10

Yes I tighten the adjuster right up so the wheel is locked then back off the adjuster until the wheel turns with a light brush of the drum


#11

In brakes, mass plays a very important role. In disc brakes, the thicker (and therefore, heavier) the rotor, the less likely it is to warp.

The same thing with drums. The more they are machined, the more likely they are to warp.


#12

In addition, many drum brake systems are designed such that the friction from the applied shoes actually assists in pressing the shoes onto the insides of the drums.

I’m going to guess that modern lining materials have higher coefficients of friction than the original Holden linings and that combined with the tendency of the friction to push the shoes into the drums due to the brake design are combining to cause the shuddering.

Understand that this is only a theory. There’s no “book” on this type of problem that I’m aware of. Which brings up another suggestion; perhaps some in-depth research on brakes is in order on this one. There may even be a Holden club that can shed some light. Granted, it probably won’t be a big club, but I’m sure those who have restored Holdens are members.


#13

@the_same_mountainbike is on the right track. I strongly recommend you search the internet for a Holden forum. That’s where you’ll find the one or two people in the world who are absolutely experts on front brake drums for Holdens.


#14

Yeah, I am a member of. Holden forum but every time i raise the topic of drum brakes everyone just says “upgrade to discs”.


#15

Upgrade to disks, if you care more about performance than authenticity.


#16

Perhaps someone on your Holden forum can at least tell you what the lining material was that Holden used and you can research from there.

I’m also wonder if, since they all recommend upgrading, this was a problem that Holdens had right off the assembly line. Is there any indication that there might be a basic design problem in the brakes themselves? Perhaps the shoe pivot points aren’t at the optimum points, or the arc radius of the shoes is incorrect?