HOW BRAKES WORKListening to your engine roar while handling a tight corner or splashing through the mud in four-wheel drive—it’s the little things that make driving your vehicle a fun experience. But you can’t forget about safety. Something has to slow you down heading into that corner or stop you when the muddy ground ends your brakes. No matter how fast your car is off the line, the amount of distance it takes to stop is more important.
Disc Brakes vs. Drum BrakesThere are two basic types of automotive braking systems: disc brakes and drum brakes. Though each type uses friction to serve the same purpose, the way they work differs.
Compared to drum brakes, disc brakes tend to be lighter and easier to service. That’s why the front brakes on your car or truck are likely to be disc brakes. While disc brakes are fundamentally more complicated than drum brakes, the added complications come with a host of advantages.
How Disc Brakes Work
When you press on your brake pedal, pressure builds in your brake lines. The pressure then acts on the cylinder inside the brake caliper. The pressure in the cylinder pushes on the caliper’s piston. The piston then acts on the brake pad, which makes contact with the rotor. The friction between your brake pads and the brake rotor is what ultimately causes your car to decelerate under braking.
There are three essential parts necessary for a disc brake to work:
The rotor is the “disc” portion of the brake, which is connected to the wheel and/or axel. When the vehicle is in motion, the rotor spins in place. The rotor must be perfectly smooth on both sides and requires a minimum thickness to work properly. Most rotors can be machined down to the minimum thickness even after they have been used for tens of thousands of miles.
The caliper holds the brake pads in place and acts as the key mechanism between the rotor and brake pad. The caliper’s pistons must move inside their bores. The caliper transfers the force from the brake pedal to the brake rotor.
The brake pads are built with one main purpose in mind: to press against the rotor when you depress the brake pedal. When in doubt, replace them. Most brake pads have wear indicators built into them. These indicators consist of small divots in the pad material that, when worn completely away, indicate the brake pads are on their last legs.
Drum brakes are a little different from disc brakes. Depending on the age and type of vehicle you own, you may have a pair of drum brakes rather than disc brakes acting on the rear axle of your vehicle.
How Drum Brakes Work
Rather than a rotor, drum brakes use a cylinder to stop your vehicle. Hydraulic fluid is forced into the wheel cylinder, which in turn pushes the brake shoes outward against the drum. That drum is attached to the wheel, and the friction from the brake shoe brings the axle to a stop. As with disc brakes, drums have a minimum thickness specification.
Drum brakes can often be machined to like-new condition, allowing you to avoid replacing them when they wear out. In general, drum brakes tend to last longer than disc brakes. This has more to do with the fact that they are often found on the rear of most vehicles that have them, rather than any sort of increased durability.
The Front Brakes Do the Hard Work
Up to 90% of stopping power is contained within the front brakes. Even if your car or truck did not have any brakes on the rear, you would still be able to stop effectively. Alternatively, if you chose to use just your rear brakes, you would find your vehicle stops much, much slower. Because so much force is applied to the front brakes when stopping, they tend to wear out must faster than rear brakes. This is true whether you have disc or drum brakes on the rear of your vehicle.
Brake Problem Warning Signs
- Brake warning light comes on
- Car pulling to one side when braking instead of stopping in a straight line
- Brake pedal is mushy or very hard to depress
- Wheel(s) are excessively hot after short drives
- Brakes grind with continuous loud metallic noise when applied
How long do brakes last? Most new cars require brake service during the first 30,000 to 42,000 miles. You should also inspect them for wear before the winter and summer seasons because extreme temperatures may negatively affect your brakes. If you start to suspect that your car is having braking issues and you aren’t sure where they are stemming from, bring it to Pep Boys for a Brake Inspection.
Brakes are arguably the most important car parts, even if they aren’t fun to think about. With routine checks and the occasional replacement, you can ensure that during those times spent enjoying your vehicle, you’ll never have to worry about when it’s time to stop.
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