Hooniverse 101- Let’s Do Drum Brakes (Part One)


Stopping your car is almost as important as making it go, and whether you’re a left- or right-foot braker, it’s safe to say you want to make sure your car’s clampers are up to the task. For our next installment of Hooniverse 101, we’re going to dive into the function and maintenance of those most mysterious of brake types – the drum brake.

Now, as a reminder, Hooniverse 101 is intended as an introduction to auto maintenance and function, so many of you will be ahead of the curve when it comes to much of what we’ll discuss. Your input on the discussion, in the comments below, is well appreciated.  After all, this is for those of us who don’t know how their vehicles work, but are eager to learn the basics.

When I did the last Hooniverse 101, on oil changes, I got a lot of feedback that Drum Brakes would make for a valued topic, so here we are. It should be noted however that due to the number of minor differences between various makes’ and models’ drum brake designs, you shouldn’t tackle this job without a good manual or detailed instruction for your own particular car. This however, will hopefully give you a good preparation for what you could expect.

Spin the Drum Slowly

Drum brakes have been around for seemingly forever, and were the stoppers of choice for most of the last century. They supplanted externally clamping brakes – literally a friction material-lined metal band that through mechanical means would squeeze either an axle or a wheel on the car’s driveshaft.

Needless to say, as cars became more capable at traveling at speed, the need arose to safely retard that capability, and in the 1930s the industry made a shift from mechanical brakes to hydraulic. The braking mechanisms of today are, at their basics, riffs on these decades old designs.

But what about drum brakes? How the heck do they work? Well, pretty simply as you will see in my professional-grade illustration below, or in this lengthy video produced by the Army.


The drum brake is composed of four basic parts that stop the car, and a bunch of others that help keep it bolted together and provide other functions. We’ll get into those in a minute, but to start out let’s review the basics.

Like I said, there are four basic parts in most drum brakes that are required for them to function. Those are –

  • The brake drum, which is the part that rotates with the wheel.

  • The brake shoes, which come in pairs, are covered in a sacrificial material, and are pressed against the inside of the drum by hydraulic pressure.

  • The hydraulic or wheel cylinder, which converts hydraulic fluid pressure to mechanical pressure against the shoes.

  • The return springs, which serve to pull the brake shoes away from the drum preventing drag and heat generation.

That’s pretty much it. Now, all drum brakes are not created equal, but most of them work in this fashion- the hydraulic cylinder sits at either the top or bottom of the brake backing plate. Opposite that is a pivot block that serves as the fulcrum against which the brake shoes are pushed.

When the brake pedal is pressed, hydraulic fluid is sent under great pressure from the master cylinder to the wheel cylinder. A piston in the wheel cylinder pushes outward on either side on the ends of the brake shoes which are resting against the piston ends.

The pivot block serves to align and keep the shoes from simply being pushed through an arc by the expanding pressure. Because of these factors, the shoes come into contact with inside surface of the rotating brake drum. As the shoes rub against the drum, speed is converted to heat and brake dust, and the car is slowed by the friction.

Got it?

Some things to keep in mind – there are typically additional parts inside the brake drum and poking through the backing plate. This is the parking or emergency brake, which is a cable-operated mechanical means of pushing the brake shoe against the drum lining and keeping your car from rolling down the hill.

There are also drum brakes that lack a Pivot Block, instead having a pair of wheel cylinders – one top and one bottom – that each act on a separate shoe. While they’ll look different their basic function remains the same as that of the Datsun I’m using as an example.

The most important thing to remember when changing your drum brake’s shoes or rebuilding a wheel cylinder is to work on one-side at a time and use the other as a benchmark for where all the parts go. With the number of springs, and the fact that there are two fairly similar looking shoes with which to contend, this is critical advice.

Never tackle your brakes for the first time by simply disassembling everything thinking you’ll remember the orientation of the springs, or how the hand brake levers fit. Also, take a lot of pictures as you take stuff apart so you’ll at least be able to retrace your steps photographically.


Okay,  let’s go through the step-by-steps of changing out the brake shoes on this 1970 Datsun.

First thing you will need to do is loosen the lug nuts on the wheels. Do this before jacking the car up or else you’re gonna’ have a bad time. Remove any hub caps or other encumbrances to getting to the lugs and loosen them to the point where you’ll easily be able to spin them off when the wheel is elevated and free spinning.


Next, we have to jack that bad boy up. Chock the opposite end wheels and position your jack in an acceptable place under the car – either in a factory provided jacking spot, or – as in the case here – under a well braced element like the differential pumpkin. Once the wheel are off the ground and the car is at a good height for you to work on it without turning into Igor, support it by placing jack stands under substantial frame elements.

I can’t stress this more strongly: DON’T JUST LEAVE THE CAR ON THE JACK. Put it on stands like I have, or by placing wide wooden supports under the frame where they won’t interfere with your access to the wheel arches.

One Does NotDrop the jack and give the car a gentle push to ensure that it is securing supported. Feel free to winch a bit as you do this because it would be scary if the car actually fell.

Once you are sure the car is safely supported, go ahead and remove the wheel nuts/studs completely and pull off the tires. Put them in a safe place, and you might want to go as far as bagging your nuts in a zip-lock to ensure they don’t get lost.

Before we go any further, a word about your safety. Many older cars have brakes with friction material made out of stuff like asbestos, which is gnarly stuff and bad for your lungs. Also, some of the chemicals with which we will be working are not so good to have come in contact with your skin. Because of these factors, you should invest in a good particulate mask and some nitrile gloves for protection.

Okay, back to the play by play.

DSCN2699We now have a good view of the brake drum itself. This one happens to be made of aluminum and finned, but most are cast iron and exhibit a patina of rust. You may also find that they have either a large Phillips head screw flush with the outer face near its center, or a torx head in the same spot if the car’s newish. You’ll need to back those out as they are there to hold the drum in place when the wheel is not doing so.

In this case, the drum is free floating, and only needs to be pulled off the wheel studs to be removed. Should the shoes be rubbing against the drum, or if corrosion is sticking it to the hub center, then you’ll need to take some additional steps.

If rubbing, there will typically be an access hole either in the drum face or in the backing plate where a screwdriver may be inserted and the auto adjuster (more on that later) could be backed off. If it’s corrosion, then you’ll need a liberal application of penetrating oil and a hefty rubber mallet to help break things free. Don’t hit it too hard, if it doesn’t come off with modest attention, then you may want to enlist professional help.

Also, once off you can take your drums into most parts and service facilities where, for a nominal fee, they will turn them to machine the inner surface and ensure they are not out of round.

DSCN2700In my case, the drums slid off without issue, giving us a view of the drum brake’s inner workings. Here you can see the shoes, the hydraulic cylinder, pivot block, and return springs. I measured the drums and found both to be within spec, so I didn’t bother with having them turned.

First off, just like Mister Rogers, we’re going to get those old shoes off. There are a pair of what are known as anti-rattle pins holding the shoes in place. These are made up of four parts – the pin, the spring, bottom seat, and cap. The pin actually looks like a nail with a flat end on it instead of a point. That flat end slots into a slot on the cap, and when spun 90 degrees holds the whole shebang together – along with the shoe – against the small spring’s pressure.

DSCN2702Here’s most of the tools we’ll be using to get the old shoes off and the new ones in place, and the most important of those is that pair of long nose pliers. You can use a special tool for releasing the pins, but I find that this work the best. Grab the pin with the pliers, push in and twist, and they come apart easy as pie.

DSCN2703Once the anti rattle pins and springs and caps have been removed, the next step is to pull the shoes off of their perch on the pivot block. This is easily accomplished with a pair of good sized channel locks, grasping the metal ahead of the friction material twisting outward. Once off of there, the shoes will typically have enough tension removed to slide off the perches on the other side, and out.

After those are out of the way, it’s time to do a little house cleaning. First thing is the brake’s self adjuster. That’s the little gear-like wheel on one side of the hydraulic cylinder. As the friction material wears, the adjuster pushes the shoes further outward in compensation. They work every time you apply the brakes when backing up and now need to be screwed back down to make room for the new, thicker shoes.

You do this on the Datsun by spinning the little cap in the center of the adjuster, it threads back down and I went ahead and just seated it all the way down, making sure the slot in its top was properly facing vertically.


Also, it’s a good idea should your car be a bit older to hit all of the components with a dash of brake cleaner to get rid of the grime. Make sure to put a catch basin under the brake to catch the drips, and don’t breathe that stuff in, it’s pretty bad for you.

I also recommend cleaning all of the bearing surfaces and the studs of any crud or surface corrosion as that will make for a better reassembly and eventual function. I hit everything with a rotary wire brush and it cleaned up pretty nicely.

This is also the time to check the wheel cylinder for any tears in its rubber boot or apparent leaks. Make sure that while the shoes are absent that no one pushes the brake pedal, as that will result in the cylinder popping out its piston and lots of hydraulic fluid. Not fun.

Okay, that’s enough for today. Tomorrow we’ll get into the weeds as far as putting on a new pair of shoes – which let me tell you is a lot less painful than when you are a kid shopping with your mom for Sunday go to church footwear.

Images ©2013 Hooniverse/ Robert Emslie

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39 responses to “Hooniverse 101- Let’s Do Drum Brakes (Part One)”

  1. danleym Avatar

    Hold up. Your drum brakes only have two springs? Why the hell do mine seem to have seventeen?

    1. mdharrell Avatar

      Mine each have precisely one more spring than can be removed or installed without bloodshed.

      1. OA5599 Avatar

        That's one of the parts that gets left over and discovered after the job is complete. I won't go so far as to say it can be safely ignored, but it will be ignored.

        1. mdharrell Avatar

          I apparently prefer to temporarily ignore one or more of the parts that require me to once again R&R the aforementioned spring of maiming.

    2. ˏ♂ˊ mzs zsm msz esq Avatar
      ˏ♂ˊ mzs zsm msz esq

      You know how most sons have a moment when they think their father is the greatest most manly male in the world, and then not anymore. Well, one day I watched my dad doing the drum brakes on the way in the house after track and to me he seemed again the wizard greatest man in the world.

  2. JayP2112 Avatar

    Good timing. I need to work on mine… at least check them.
    Almost 200k miles and still (as far as I know) on the same shoes and drums.

    1. jeepjeff Avatar

      Yeah. Me too. I might have been waiting for this feature before looking at mine…

  3. calzonegolem Avatar

    I replaced drum brakes once. That taught me that I want to pay someone to do them for me or get cars with 4 discs.

    1. boxdin Avatar

      Exactly !

  4. dukeisduke Avatar

    Whoa, upside-down brakes (with the wheel cylinder at the bottom). Also, do you know they make a tool just for removing and reinstalling hold down springs, so you don't have to use needle nose pliers? Here's one made by OTC:
    <img src="http://www.ntxtools.com/Merchant/graphics/00000001/otc-4591.gif"&gt;

    1. Robert Emslie Avatar
      Robert Emslie

      You can see in the tools pic that my multi-tasker brake tool has one of those gadgets on the handle. I'll stick with my recommendation of using long nose pliers.

      1. dukeisduke Avatar

        I always just used regular pliers. One finger on the head (on the backing plate) to hold the pin steady, then clamp the pliers on the cap, and push in and turn. Installation is the same. I can see how the needle nose works, though.

        1. danleym Avatar

          I know there are a handful of nifty tools for drum brakes, and for almost everything else I really like specialized tools, but I've become a pro at doing drum brakes with nothing more than needle nose pliers, 90 angle needle nose pliers, and a flat head screwdriver. I'm not saying it's the best way, but it works well for me.

    2. Kris_01 Avatar

      As a professional mechanic, I echo that this tool is the way to go (not me, the retaining spring tool).
      Got mine in a pawnshop bin full of screwdrivers for $0.50. Guy wasn't sure what kind of screwdriver it was.

    3. HTWHLS Avatar

      This tool is absolutely VITAL for drum brake repair. Ask my left thumb, left wrist and the pliers that were thrown through a '67 Squareback's rear window.

  5. OA5599 Avatar

    Before disassembling:
    1. Take note of shoe placement. Often, these are not symmetrical, with the front shoe of the pair having more or less area covered by the lining material than the back shoe of the pair.
    2. Other than removing the wheels and drums, do one side of the car, start-to-finish, before beginning on the other side. It makes the job a lot easier when you have a convenient reference to which way the pieces are supposed to fit back together.
    3. If the drums hava a lot of wear, the shoes may have worn a groove into the inside of the drum. You may need to manually turn the adjuster to back off of the adjustment enough to retract the shoes from the groove in order to get the drum off.

  6. frankthecat Avatar

    Other useful advice if you live in the rustbelt:
    If the drum is stuck on, whack the face of the drum, around the hub (BUT DON'T HIT THE STUDS,) with a 1lb sledge hammer a couple of times. If that doesn't work, loosen off the adjuster using a screwdriver through the rubber plug on the backside of the drum plate.

    1. cheapthrills Avatar

      Additional rusty drum tip:
      On most cast iron drums, there will be two threaded holes on the face of the drum. These are there to press the drum off. Thread in two bolts with the correct thread size and suitable length, make sure the holes are lined up over something solid (the metal frames of the shoes is your best bet). Tighten the two bolts, alternating side to side, until you can pull the drum off.
      I've had the anti-rattle pins snap, causing the shoes to get wedged in there all weird, and this method was the only way of getting the job done.

      1. Kris_01 Avatar

        If you are going to replace the shoes, do yourself a favor and get a new hardware kit (new springs, retainer hardware and other misc. junk you may need, like inspection hole plugs).
        If all else fails and you can't get that drum off, snip the ends off the retaining pins on the backside of the backing plate with a pair of sidecutters. Then give the drum another whack with the ballpeen. It should come right off.

  7. mdharrell Avatar

    In Part Two will you cover the Bendix torque spider employed in the rear wheel brake of HMV Freeways?
    <img src="http://www.shopezgo.com/images/TorqueSpiderforBendixBrakes.image.jpeg?size=0&width=235&mid=297fa7777981f402dbba17e9f29e292d"&gt;

    1. Alcology Avatar

      That's going to lay eggs inside of me isn't it.

  8. facelvega Avatar

    Personally, I think around 1962 was the pinnacle of automotive design. But if I ever buy a car from 1962, I'll probably swap in disc brakes. Partly this is because of their far superior performance, but mostly it's from having swapped out both in the past, and still being slightly traumatized from the drums, with the lingering fear that I'd forgotten or misreplaced one of the little parts before forcing the drum back together. Yuck yuck yuck. For me replacing the pads/shoes on a car with both is like going from replacing a light bulb to replacing the filament out of a light bulb.

    1. P161911 Avatar

      About 90% of the time disc brake swaps only apply to the front axle. The rear keeps the drums. GM recently switched from rear discs BACK to rear drums on full size pick ups.
      On C3 Corvettes GM had 4 wheel disc brakes, but kept a drum brake in the rear rotor hat. It was the parking brake. <img src="http://image.vetteweb.com/f/10444438/vemp_0401_01_z+1978_chevrolet_corvette+parking_brake_kit_install.jpg"width=400&gt;

      1. facelvega Avatar

        I'm specifically thinking I'd go all disc on an Avanti with a turner kit. Naturally for performance the fronts are what matters I don't mind a drum parking brake, as it's not liable to ever need attention, and I guess it helps keep the parking brake from sitting clamped while exposed to the elements.
        GM's switch back to drums on the low-end models is awful. They save say fifty bucks per car in production costs, and the owners get to eat several times that much money in additional mechanic's hours over the life of the vehicle.

      2. Impalamino Avatar

        "Drum-in-hat" is one of my favorite automotive terms. Up there with guibo and reluctor.

      3. Kris_01 Avatar

        That's a pretty common design nowadays on larger vehicles with rear discs (think trucks and minivans).

  9. needthatcar Avatar

    Most buses and trucks still use drum brakes. The design is pretty much exaclty the same, only huge-r.
    Also, did you make it to the 25% off sale at JC Penney?

  10. Stu_Rock Avatar

    In some very compact drum brake setups, you need to remove the hub in order to be able to reach the springs. I loathe those designs.
    Also, wear safety glasses while working on drum brakes. You don't want anything to sproing into your eyes.

  11. Gooberpeaz Avatar

    Self -adjusting drum brakes! What is this wizardry you speak of?

  12. Dean Bigglesworth Avatar
    Dean Bigglesworth

    When finished, it should look something like this, right?
    <img src="https://dl.dropboxusercontent.com/u/74465213/Falsterbo-308.jpg&quot; </img>
    The whole car was so spotless that just starting it would ruin it. So it was absolutely useless.

  13. Alcology Avatar

    You forgot the most important part: check the emergency brake and make sure it's not on.

  14. joe Dunlap Avatar
    joe Dunlap

    What has remained a mystery to me for the 43 years I've been a tech, is why in heavens name drum brakes continue to exist? Their performance in every phase of use is inferior to discs. They have more moving parts (read failure points) that make them more labor intensive to build and maintain. The only area they come close, but still fall short in is weight. Is it possible they are cheaper for the manufacturers to install as OEM? Hardly seems possible, unless they are getting container ship loads of them from SE Asia, assembled by 6 year olds. Please, someone enlighten me.

    1. salguod Avatar

      Actually, for a given swept area, I believe that drums will produce more stopping power than discs because they are self engaging. As they produce force, the shoe wedges and produces more force.
      Of course, that's only true going forward, in reverse it's the opposite.
      Oh, and it's only true on the first stop with cold brakes. Once they heat up, they don't cool fast and fade sets in.

      1. joedunlap Avatar

        Not more stopping power, just less pedal pressure. Ultimately stopping power is defined by the tire/road surface interface.

  15. craymor Avatar

    and another add on, if you remove both wheels and drums, you can use the other side as a guide for where all the crap goes! just remember it's a mirror image, not the same.

  16. SSurfer321 Avatar

    I did drum brakes once. And one of the damn springs popped off as I was driving. I don't know if I've heard heard such an awful noise as spring and metal bits grinding around in the drum.
    My truck has discs at all corners and the Subie has rear drums.

  17. salguod Avatar

    First, "wood supports"? Uh, no. Go buy proper stands, period. If you can't afford proper stands, you can't afford to work on your own car. Cars are heavy, flesh is fragile.
    Second, that small flat head screw isn't really necessary and will likely be rusted in place if you live in the snow belt. It's only there to keep things together at the factory. Don't waste too much time trying to remove it if it's frozen, just drill the head off.
    Third, many drums have threaded jack holes in the face to help in removing rusted on drums. The trick is finding the right thread. Once you do, screwing in the proper sized bolt puts pressure on the hub, forcing the drum off fairly easily.
    Fourth, pull the drums off both sides, but only disassemble one side at a time. That way you'll always have one side to look at for where that 17th spring goes.
    Lastly, older cars like my T'bird, the drum is assembled to the hub with a single castle nut and removing it exposes the wheel bearings and races. Be prepared to pack bearings if you're working on one of those.

  18. C³-Cool Cadillac Cat Avatar
    C³-Cool Cadillac Cat

    Oh, drum brakes, how I don't miss your antics.
    The campground on the south side of Fairbanks, AK, has a spring for a 1999-2003 Grand Vitara in the undergrowth.
    Driver's side rear was dragging, so I dove in, knowing full well what I was in for, having had more than a couple of 4-wheel drum vehicles in my time.
    The spring launched, as I suspected it would, never to be seen, again. Meh. At least the Suzuki dealer in Vegas stocked & sold just that spring.
    Drum brakes are the pall of automobiledom. The ONLY upside to them is they do not drag when not engaged (or broken). This is why at 200K miles, you may have OEM shoes on the rear.

  19. HTWHLS Avatar

    Another couple of add-ons:
    My father always told me whenever you unbolted a tire, to lay it down under the car, centered on the frame, especially if you were removing two wheels (such as both rears or fronts). This way if the jack slipped and jack stands wobbled and the car slipped, it would not hit the ground. This tip saved my life, literally. (Although jack stands are light-years better than they were.)
    Some drums may have a little crazy washer (looks like a star washer with points sticking up). This is a Timmerman clip and was used at the factory to hold the drums on. They come off pretty easily and do not need to be replaced.