The Underappreciated Drum Brake

@wha who?
Finally a fellow who agrees that the drum brakes got a bad rap. Here is my question, if disc brakes are so good, why do semi trucks still use drum brakes when they haul tremendous amounts of weight? I have driven a moving truck with power disc brakes, they were hydraulic, it was scary stopping it. I have driven another moving truck with good ol drum brakes, airbrakes. It stopped very well.

Lets hear it for the un appreciated drum brakes.


Thats my point, why dont we go back to properly sized drum brakes, they worked just fine. The good ol days.

I was told that relined brakes still may contain asbestoes which while it was a cancer causing agent, it does its job really well.

@WheresRick I doubt that very many shops would accept beer as payment

"if disc brakes are so good, why do semi trucks still use drum brakes "

Actually these days air-actuated disc brakes are becoming more and more common. But using compressed air helps deal with one of the traditional weaknesses of drum brakes, heat dissipation. With air brakes like you see on semis, there’s no brake fluid to boil.

Can anyone tell me why semi trucks which weigh 70k lbs loaded still use our good friend the drum brake on all wheels? Why is this? Surely the could make a disc air brake, they may who knows?

In a nutshell, drums aren’t as good as discs and I’d certainly rather service disc brakes than drums with an assortment of levers and springs; the latter which have been known to go flying.
However, I don’t think drums are death personified.

On the other hand, if you ever had to replace a set of brake shoes on an old Subaru FF1 (and I did a few back in the 80s) you would be cursing the day someone invented brake shoes. They were mounted inboard on the front drive transaxle and flat rate labor time was around 8 hours on a brake job.

A similar procedure would be building a ship in a bottle.

I’ve done both on my cars and have to say that buying a car with rear drums would be a deal breaker for me. The last ones I worked on, think it was the Park Ave, didn’t even have the slots to adjust the shoes down or up. You needed to measure them before putting the drum back on. No thanks.

You guys have me all amped up and now I cant sleep. Just to prove a point there is a 69 caprice on ebay with a 427 engine and 4 wheel drum brakes. I may just buy it to prove a point. A big heavy car with a powerful engine stopped by our red headed step child, drum brakes. Oh it cant be.

I could buy it and go thru the brakes and get the shoes relined for 30 dollars worth of beer at my friend bobbys shop. Then I could go buy a rebuild kit for 30 dollars and rebuild the carb and have a car that is as good as new because the car has a timing chain and will last another 40 years.

Let me ask you this, Do drum brakes ever get pulsation? Our pretty boy the disc brake sure does.

My 59 Pontiac had four wheel drums and was a pretty heavy car. Think it was $15 new shoes but what a hassle and sure didn’t have the stopping power of my 09 Pontiac with 4 wheel discs.

You don’t suppose there might be a reason that those guys who do resto-mod / pro-touring restorations always see fit to stuff big Wilwoods under those do you?

“A big heavy car with a powerful engine stopped by our red headed step child, drum brakes. Oh it cant be.”

It the same car had a set of disc brakes , it would stop sooner, more consistently, and with far less fade under repeated use.

I’ve owned some big block muscle cars with drums and they were never a problem. As Clint Eastwood said in a movie; a man’s got to know his limitations. :slight_smile:

Regarding Bing’s Park Avenue, I’m not sure on that model but in what was no doubt a penny pinching move on the production line some car makers omitted the removeable plugs for rear shoe adjustment.
However, they would dimple the backing plate and a punch and hammer were to be used to knock out the oblong dimpled segment. Rubber plugs were to be purchased and added after the shoe adjustment.

The route manager for the Coors distributor dropped by the dealership one day around lunchtime and left me a free case of beer as a thank you token for fixing his car. The car had been in the shop half a dozen times over several weeks with a different diagnosis and cost each trip. He finally balked at a valve job diagnosis on a 30k miles car. The problem? One dead plug wire that was found inside of 2 minutes.

@fodaddy Those guys that do that have big wallets and small ways. They are trying to be big shots and 4 wheel disc is the in thing right now, so they do it to fit in.

It the same car had a set of disc brakes , it would stop sooner, more consistently, and with far less fade under repeated use.

John Muir of the vw idiot book fame said to drive in a way which brake use was minimal. No reason for repeated use, downshift. Downshift.

I don’t like disk brakes because they always drag, it is part of their design to have close pads, if they came up with a design for disk brakes that was lighter then drums, and that the pads were able to fully retract, then I would think about them, but as they are they weigh more, and slow you down, try it, coast to a stop, and feel your wheels, if you have disk brakes they will all be warm, and the drums cold.

Discs brakes rely on the disc knocking the pads back into the caliper for clearance drums dont.
This means there is ALWAYS more resistance on a disc brake setup as the brakes always drag a little.

The downside to disk brakes for me is that they’re open to the elements. When you don’t drive every day (and then when you do drive, you don’t use the brakes much or very hard) the disk surface rusts.

The drum brake is going to be lighter and brake harder initially than a disc brake of equal size because their is a greater friction area.

Manufacturers went to discs BECAUSE IT WAS CHEAPER FOR THEM !

ok4450 Yeah I probably should have just knocked the plug out, in fact still have the unopened package of the rubber plugs. But the factory service manual called for measuring them and even had a special tool to do it. I broke the spring tool anyway so have no intention of ever doing drum brakes again. ('Spose I’ll regret having said that and have to eat my words.)

@bing Dont let em get in your head bing, I would not let the fact a car had rear drums scare me away from it. Embrace rear drums, that way you get best of both worlds. Dont fear the rear drum, embrace it. If you could still buy a new car with 4 wheel drums I would, it completely floors me that they no longer make cars with front drums. I think 1977 was the last year for front drums and that was on the vw bug.

Theres many problems not found with drum brakes(warped rotors, stuck calipers, etc).

Brakes don’t prevent an accident, a driver does.

What do you mean there’s no brake fade with disks? Disks will fade just as easy as drums. Pretty much any type of brake that uses contact friction will fade when they get hot.

Disks will fade just as easy as drums

One of the main benefits of disk brakes is their ability to resist fade due to their superior cooling over that of drum brakes. Don’t even try to dispute that one.

WheresRick, drum brakes had their time and place as the primary brake technology, and they do have “some” benefits that disks don’t enjoy. But please step back for a moment to look at how you’ve so lost the extreme position you’re trying to defend.

@WheresRick , you don’t take your cars to the track or autocross them do you?


“…why do semi trucks still use drum brakes when they haul tremendous amounts of weight? “

Because they have to balance brake pots and air disk brakes and the forces during braking. When the brake drum heats up, its surface actually moves away from the lining as the drum expands. Conversely, when the disc heats up, it moves closer to the pads. So, they put more stress on the disc brakes as the braking system heats up. The drum brakes apply less braking force and the disc are applying more.

They are now going to disc brakes, why? Because the Federal Motor Vehicle Safety Standard (FMVSS) 121 reduced stopping distance regulation. It now requires a loaded Class 8 tandem axle tractor with 59,600 GVWR or less to stop in 250 ft. from 60 mph, down 30% from a previous standard of 355 ft. So, you’re going to see a lot more tractors and trailer with disc brakes.

Having driven, and replace both types, I’ll take disc brakes any day. Easier to change pad than shoes, no adjustment required, better stopping distance, less fade, better wet and mud performance, and last longer. The big one of course is no adjustment needed, if you happened to be the type of person who didn’t back up much, your drum brakes wouldn’t self-adjust, IF your drum braked had self-adjusters.Not a worry with disc brakes, they adjust themselves.

Not saying that drum brakes were bad, it’s just that disc brakes are better in most cases.