Drum Brake tutorial

Drum brakes.  Some think of them as archaic technology from a bygone era of the first cars on the road.  Others view them as an overly complicated brake type held together by too many parts that are too difficult to replace and maintain.  I view them as the brakes that are not only found on the rear axles of many cars, even to this day, but they are also found on most semi trucks, even today.

Drum brakes operate on the same principle as disc brakes do, hydraulic pressure is used to operate the brakes generated by the brake pedal, except where a disc brake set up presses the brake pads into a rotor, drum brakes are operated through hydraulic pressure that actuates a wheel cylinder, which expands pins that press the shoes on to the inside of a brake drum.  Brake drums are typically made of iron, and, like brake rotors, can be machined and reused until their maximum diameter is reached.

Drum brakes have more moving parts than a disc brake, including springs to retract, spacers, self adjusting parts, cables, etc.  They have more parts, but I believe that if you take your time and have the right tools, you can do this yourself.

I would suggest that if you have any doubt as to your ability to do this job, you should consult a professional, as brakes are pretty important safety item and they need to work properly.


I recently had occasion to replace the drum brakes on my Durango, and I decided to document the process.

First thing is first, this is what you will need to do this job:

I have here jack stands, a floor jack, wheel chocks, pliers (needle nose and standard), a brake tool (that has a spring tool, a tool for installing springs, etc.), a large hammer (not pictured), one small and one large screwdriver (also not pictured), and of course new brake shoes and brake hardware (springs, pins, etc.)

Set the wheel chocks on the front wheel to prevent movement, and raise the rear axle enough to spin the tires, then secure the rear axle on jack stands. Remove the tires, then remove the drums.  Use the large hammer to smack the sides of the drum to aid in removal.  This will help dislodge any rust or build up that might keep the drum stuck on the hub..  If the drum does not come off, you will need to spin the star wheel to retract the shoes.  There is an access plug on the backing plate, usually covered by a rubber plug, which allows you to do this.

Above is the access hole for the star wheel.

And this (above) is the star wheel.  The big flathead screwdriver will be used to push a spring back and the small screwdriver (also a flathead) will be used to spin the star wheel teeth.  Generally, these need to be spun upwards, but if you are unsure, spin the star wheel and check to see if the drum moves at all.  If it moves freely, you are going in the right direction.  If the drum will not move, that's the wrong way.  Now once the drum is removed, you will be looking at this:

As you can see, there are the springs I mentioned earlier.  There are also pins that are held in place by springs and cap locks, the star wheel on the bottom, a parking brake cable, more springs, and the shoes.  Not visible is the parking brake cable that runs from the assembly to the parking brake pedal in the passenger compartment.

The first things to get removed are the upper springs.  Using the spring tool, place the tool over that top retaining pin (it's fixed in place) and rotate the tool, then pull back.  The spring will come off.  Repeat for the other spring.  Set these aside for reference in a similar fashion to how they were arranged on the brake for reference.

The top springs are first in line for removal.

                  Using the tool to remove the spring.  

Next, use a pair of pliers or a brake spring tool to remove these caps. They are rotated so that the slots in the caps line up with the tabs on the pins.  They can then be removed, along with the springs behind them.  The pins slide out of the back of the mounting plate.

Above is a close up of the pin retainer. Take note of the slot that is in the center, this is what will need to be aligned with the end of the pin that retains the spring and in turn, the brake shoe.  The shoes may now be removed.

The next piece of the puzzle is to remove the parking brake cable and pivot assembly, as indicated by the arrows. This is simple to remove as at this point the cable can be removed with little effort.  Set this aside as well.  There is a part behind the cable eye that acts as a spacer between the cable and the shoes. This also, like almost everything else, needs to be removed.

Finally, remove the star wheel, parking brake pawl and their springs.  Take note of a couple of things, most importantly its orientation and that it can be adjusted.  If you are reusing the star wheel, my suggestion is that it be cleaned up and the threads lubricated, lightly, with either a WD-40 type oil or anti seize.  Either will work but this needs to be applied sparingly,

Now for the reassembly...

When installing the new shoes, looking at the old ones, if you placed them on the ground as they appeared when you removed them, that will tell you how to position them.  From there, installation is started by installing the pins, springs, and caps to hold the shoes in place.  Next is the star wheel and spring used to keep the wheel from moving.

Above is the star wheel (shown on the old shoes) which needs to be adjusted to its minimum length.  It will be adjusted later in the procedure. Not pictured is the spring which is used to keep the wheel from adjusting itself. Additionally this is the time to reinstall the parking brake cable, pawl, and retainer spring.

Once the star wheel, parking brake pawl and their springs are installed, it is time to install this bar with the spring and spacer on one end between the shoes.  There are notches in the shoes that these ends are installed into to hold it in place, just below the notches for the wheel cylinder pins.

The above picture should give you an idea of where this spreader bar goes onto the shoes.

Above is a retaining clip that also helps hold the brake shoe in place. install a new one at this time.

The next step is to install the cable inside the shoe between the pin at the top and the parking brake pawl on the inside of the shoes, do not forget the spacer on the top pin.

Finally, set up the top of the shoes with the wheel cylinder pins in their proper spaces.

To adjust the brakes so that they work (on all models that use brake drums):

You will need to expand the star wheel until the brake drum just barely fits over the shoes.  When this is done correctly, you will hear a slight drag on the drum by the shoes.  You can also adjust the shoes via the access slot on the back of the backing plate.

You can use this diagram below to reference the parts of the drum brake system.

1. Front (leading) shoe.
2. Rear shoe.
3. Small upper spring (May vary depending on model.)
4. Large upper spring (may vary by model.)
5. Parking brake internal cable and pivot. (not shown-retainer for bracket.)
6. Upper pin,
7. Spacer (may not be present on all vehicles.)
8. Spreader bar with spring and spacer/keeper.)
9. Pin cap, spring(under cap) and retaining pin (under cap.)
10. Lower spring.
11. Star wheel.
12. Parking brake pawl and cable connection..
13. Pawl retaining spring.
14. Backing plate.

Not pictured: retaining pins as described, star wheel access slot.