No matter where you drive, a working set of brakes can make the difference between avoiding an accident and being part of one. What can keep your Hyundai's brakes from working their best? With several systems involved, there are a lot of things to look at when trying to find the problem.
When you push down on the brake pedal, the lever pushes a rod through a tube inside the master cylinder. The master cylinder has a fluid reservoir on top linked to this tube, adding more brake fluid as needed. To reduce the amount of pedal force required, the brake booster uses vacuum pressure from the engine to help push the rod through the master cylinder.
From there, the fluid passes through a series of steel lines until it's near the wheels. The final stretch between the hydraulic system and the calipers and wheel cylinders is reached using brake hoses. These hoses are designed to flex, allowing them to move with the suspension.
On cars with Anti-Lock Brakes (ABS,) there's a valve body attached to the steel lines and a toothed metal ring called a “reluctor ring” or “trigger wheel” on each hub. Next to the trigger wheel, there's a small magnetic sensor. As the wheels spin, the teeth on the wheel spin past the sensor, letting the ABS computer know how fast the wheel is moving. If the speed on one wheel drops suddenly, the valve body can release some fluid pressure, reducing braking force to keep that wheel from locking. This prevents skids, shortening stopping distances and maintaining vehicle control. On cars equipped with traction control, the valve body can also increase fluid pressure, applying the brakes on individual wheels. This helps the tire keep grip on slippery surfaces. The Traction Control System (TCS) computer uses the ABS sensors to detect sudden increases in wheel speed, applying the brakes as needed.
Take off a front wheel on any Hyundai, and you'll see a large metal disc behind the wheel studs. This is the brake rotor. Since it's mounted on the hub, it spins with the wheel.
Over the rotor, there is a bracket that holds a pair of brake pads. It's mounted to the suspension hardware, so it remains stationary. A brake caliper mounts on this bracket. The caliper has one or more hydraulic pistons that push the brake pads against the rotor. The friction between the rotor and the pads slows down the vehicle, turning momentum into heat.
Each time the brakes are used, a little bit of the pad and rotor material is worn off. The pads have “indicators,” small metal tabs that extend slightly past the backing plate. When the pad material has almost completely worn off, the indicator will make contact with the rotor, making a constant squeaking noise to let you know it's time to replace the pads.
The rotor acts like a large heat sink, absorbing the heat from braking and transferring it to the air as it spins. Front rotors have fan-like channels in the center to pull air through, aiding with cooling. If the rotor gets too thin from wear, it can overheat. Technically, rotors can't warp because they can't get hot enough to affect the metal. However, they can get hot enough that they warp the surface of the brake pads. In turn, this causes the pads to cut grooves into the rotor's surface. This reduces contact between the brake and rotor, and in turn causes pedal pulsation and reduces braking force.
Some Hyundais use drum brakes on the rear wheels. The drum spins with the wheel just like a rotor, while the braking system underneath pushes C-shaped brake shoes into the drum to slow down the vehicle. The shoes have a lining that's similar to the material on brake pads. Like disc brakes, use of the drum brakes wears down the drum's metal surface and the shoes' linings.
Remove the drum, and you'll see the braking system. The shoes are held onto a backing plate using spring nuts along with a set of springs that link the two shoes together. At the top of the plate, a wheel cylinder uses hydraulic pressure to push the shoes into the drum. The body of the cylinder holds two seals with pins on the ends. As fluid is pushed into the cylinder, it moves these pins outward, swinging the shoes against the drum. To compensate for wear, a brake adjuster slowly unscrews as the brake is used, pushing the shoes further out to reduce the distance between the shoe surface and the drum.
If your Hyundai has rear disc brakes, it probably has a “drum in hat” parking brake. Remove the rotor, and you'll see a complete drum brake system, minus the wheel cylinder. This uses the inside of the rotor's center, called the “hat,” as a drum. With both drum and disc-equipped cars, the brake is operated using a lever linked to a cable running between the shoes and the parking brake lever. Drum in hat brakes push both shoes into the drum, while drum parking brakes only push the rear shoes into the drum.
Some newer Hyundais like the Equus use an electric parking brake. Instead of a lever, the brake is engaged by a switch on the console. This activates a servo motor inside the brake caliper, which uses a screw mechanism to clamp the brake pads onto the rotor. The mechanism is housed in a plastic box at the rear of the caliper.
Problems with Hyundai Brakes
Pads, rotors, shoes and drums are wear parts, but the life of these parts varies widely depending on driving conditions. If you've spent any time here in Birmingham, you know our awful rush hour traffic can quickly wear out the best brakes.
When replacing shoes, it's also a good idea to replace the springs to ensure the braking system is under the correct tension. Hyundai packages drum brakes and parking brakes as a complete kit, including the shoes, springs and adjuster.
If your Sonata's brake calipers are locking up or aren't providing much in the way of braking force, make sure this issue isn't under a recall. Hyundai issued one for vehicles built between 2011 and 2014 due to cracks forming in the calipers.
Broken hand brake cables aren't uncommon on these vehicles, especially in areas where salt is used heavily on the roads. In severe cases, corrosion can effect the function of brake calipers.
Where to Get Brake Parts for Your Hyundai
OEPartsMart.com specializes in Original Equipment Parts. These are factory parts built by Hyundai and their partners for your vehicle, so they fit and function just like the parts used when your car was built, and they come backed with a factory warranty. Our site makes it easy to find what you need by letting you search by part number, VIN, model and keywords like “rotor” and “parking.” Have questions? Call or email us to talk to our staff of professional parts people.