Your brakes have a tough job to do. Every time you step down on the brake pedal, various mechanisms — calipers, pistons or cylinders — grip onto your brake rotors or drums hard enough to generate the friction needed to slow you down. These mechanisms are called brake actuators and they’re some of the most important parts on your car as you expect them to work day in, day out, without fail.
Types of Actuators
There are two types of brake actuators found on modern vehicles. The most common by a huge margin are brake calipers. Calipers house the pads that are used to squeeze your car’s brake rotors and they contain small cylinders (pistons) that are hydraulically activated to move the pads onto the brake disc when you ease onto the pedal.
Once upon a time, wheel cylinders (which house the pistons in a drum brake) were more common than calipers on a disc brake, but technology has largely pushed drums to the rear axles on entry-level automobiles. Drum brake wheel cylinders push a pad of their own — called “shoes” — against the inside of a drum in order to create the friction needed to stop.
Which Is Better?
When it comes to evaluating brake actuators, calipers have several advantages. The first is that the surface of a rotor is much better at dissipating heat than the inside of a drum, which means the pads don’t see their stopping power fade nearly as quickly as the shoes in a drum design. The second is simplicity: A drum piston is relatively complex and works together with a number of springs and other components that need to stay properly adjusted (usually an automated process), while a caliper is a straight-forward, free-standing housing for one to six pistons.
Which Brake Actuators Are on My Car?
To figure out what type of brake actuators are used on your own personal vehicle, take a look through the spokes on your rim: If you see a flat disc staring back at you, with a somewhat curved lump straddling it near the top, then you have disc brakes. If instead you’re looking at what seems to be a hat-shaped cover over the center of the hub immediately behind the wheel, then you have drum brakes. It’s not uncommon to see some types of vehicles mix and match the two — particularly pickup trucks, which until recently all had drum brakes at the rear — but unless your car hails from the ’60s, you’ll find discs on the front wheels.
For more information on brake actuators, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.
Photo courtesy of Morguefile.
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Source: NAPA Know How