A couple weeks ago I wrote a post about the different ways that you as a driver engage the parking brake. This week let’s look at the different ways parking brakes work.
The most basic, and on cheaper and older cars the most common, are drum brakes. Normally, during regular braking, the hydraulics push out with the wheel cylinder, pushing the shoes against the drum. When you pull on the parking brake lever, or push on the pedal, it pulls a cable that then pulls on a lever in the drum brake system, which mechanically pushes one or both of the shoes outwards.
Common on many trucks and larger cars is the disc-drum combination. Sometimes referred to as “top hat” rotors because of how big the middle part is compared to regular rotors. For regular braking there’s a caliper that grabs the rotor, but for the parking brake there’s a whole drum brake system inside, working just like it would in regular drum brakes, with the cable pulling a lever.
This is a much simpler system than the drum brake-based types. The cable pulls on a lever that pushes the piston outwards mechanically rather than hydraulically. The caliper piston is threaded like a giant bolt, which is how the rotational motion of the lever translates into linear motion. The downside of this is it makes brake jobs take a bit longer, because instead of being able to simply push the piston in, you have to use a special tool to turn the piston back into the caliper. Another downside is I’ve known these calipers to fail and seize up more frequently than regular calipers.
Electric Parking Brake Caliper
Electric parking brakes work much the same as the caliper style above. The main difference is that instead of the lever it just has an electric motor that moves the piston. Just like I said in the other post about parking brakes, you don’t have as much control over the application of the brake as with cable-operated parking brakes, making it mostly usable for just parking. Another downside is that you’ll need a scan tool to tell the computer to move the piston back in when you go to change the brake pads, or you’ll have to go to the dealer.