Most vehicles have rotors and calipers on the front wheels (disc brakes ) and drums and shoes on the rear (drum brakes), and sometimes drum brake replacement is needed. The replacement process involves two major steps: removing the drum and (possibly) replacing or re-tooling it and replacing the shoes.
How Drum Brakes Work
Drum brakes work by having the shoes, which are on springs to pull them away from the inner surface of the drum (the smooth braking surface) push out against the drum when hydraulic pressure from the brake lines is applied. The friction of the shoes pressing against the drums slows the vehicle by converting its moving momentum into heat.
Over time and use, the shoes eventually wear down and the pads on them become thin. If left for too long, they will scrape against the drum's braking surface, marring it.
Drum Brake Replacement
Drum brake replacement is actually fairly easy. The tire is removed, exposing the drum. It should slide right off (sometimes a little coaxing by hitting it with a rubber mallet might be required, to break tension that may have occurred). The drum can be inspected for grooving or marring of its braking surface. If required, it should be turned to make it smooth again or replaced, as needed.
The brake pads are shoes facing left and right. The side that equates to the forward movement of the car is called the Primary Shoe and the rear of the vehicle is the Secondary. These can be replaced by removing tension springs. Replacement is the reverse process and usually tension springs should be replaced as well.
Drum Brake Replacement: Easy DIY or Mechanic Job?
Replacing drums and shoes is actually one of the easier home mechanic DIY projects that can be done with few tools and just a little knowledge. Next to changing oil the filters, it's likely the most common DIY mechanic job out there.
Brake Shoe Replacement
Most cars and light trucks have disc brakes (rotor, caliper) and drum brakes (drum, shoe) on the front and rear respectively. Over time, the pads/shoes and rotors/drums need service and replacement in order to continue proper function. Since the brakes are your car's number one mechanical safety feature, they should always be well tended.
To replace the shoes, you'll need to remove the drums. Removing the tire usually exposes the drum, which can then be pulled off without any further tools. Inspect the insides of the drums (the braking surface) to be sure they're smooth and unmarred. Clean with brake cleaner if they're okay or have them turned or replaced if required.
Removing the brake shoes is a matter of pulling off the tension springs that hold them in place. The shoe that points towards the front of the vehicle is the Primary Shoe and the other, pointing rearwards, is the Secondary Shoe. Usually the heaviest tension spring will run between the two shoes and over a pivot point pin at the center of the wheel hub.
Other springs will be the adjusting screw spring at bottom or top (called the heel and toe of the shoe) and likely a cylinder keeper spring which lightly holds the shoes into the hub where the wheel cylinder (the hydraulic cylinder that pushes the brakes outward to the drum).
Removing the heavier spring(s) first and working your way outwards is recommended. There are special brake spring tools that are low cost and very much recommended to simplify this. Using needle nose pliers or similar tools can work, but may bend the springs uncessarily when they are installed again.
It's recommended that the tension springs be replaced as well. Most automotive supply shops have brake spring kits for just a few dollars.
Replace the shoes and springs in reverse order, followed by the drum.
Drum Brake Replacement: Easy DIY Job
For the home mechanic, drum brake replacement is one of the easiest do it yourself jobs you can do.