If you have ever ridden a bicycle fitted with a hand brake, you probably know the basics when it comes to brake pads. Think about it: you pull a brake lever that pulls on a cable that, in turn, pulls on a clamping mechanism called a caliper. The caliper suspends a pair of brake pads, made of a variety of compounds, along the sides of the wheel. When you grab the brake lever, the caliper constricts and squeezes the pads against the side of the wheel, creating friction to slow and stop your bike.
The brake pads on your vehicle work the same way. Well, not exactly the same, but very nearly so.
What are brake pads?
Brake pads are components of a disc brake system on a car, truck, or SUV. While many automobiles of the past, and some trucks of today, include drum brakes, the majority of vehicles on the road feature disc brakes.
Where a bicycle uses a cable, automotive brakes rely on hydraulics. In a disc brake system, you press on the brake pedal that activates a hydraulic pump (the master cylinder) to exert pressure through a series of tubes (brake lines) to the calipers located near your wheels. Each caliper holds a pair of brake pads that are sandwiched around a heavy metal disc called a brake rotor. The rotor is attached to your wheel and spins on a wheel hub and set of bearings.
When your vehicle is moving and the tires are rolling, the brake rotor is spinning along. Hit the brakes, and the caliper forces the brake pads against the spinning rotor, creating friction and heat. Your brake system converts the kinetic energy of your vehicle-in-motion to thermal energy, heat, as the brake pads grab the rotor.
Your brake pads contain a material that is designed to create friction when they press on the rotor. Like bicycle brake pads, the material on automotive pads can be comprised of different compounds with varying properties – organic pads for smooth and inexpensive performance, semi-metallic pads for heavy duty and high performance, and ceramic pads for smooth, quiet, extended, but expensive performance. The type of pads you choose will affect the performance of your disc brake system.
With any type of brake pad, the friction material is sacrificial, meaning it will wear away over time and require that your brake pads be replaced every so often.
How can I tell when it is time to replace my brake pads?
So, if your brake pads wear out and need to be changed now and again, how do you know when it is time? Well, it is best to have your brakes inspected at regular intervals – say, when you have your oil and filter changed. Otherwise, your car will probably tell you. And if you don’t pay attention to the signs, your car will let you know in a louder voice.
The friction material on your brake pads needs to be at least 3-6mm thick. A visual inspection by a trusted technician can reveal how much life is left in your pads. Worn-out pads will make it harder to stop your car within a reasonable distance. Severely worn pads will cause damage to other parts of your brake system.
Because of this, safeguards are built into the system. For example, most modern vehicles have a low brake pad indicator lamp or some other early detection notice on your dashboard. When the brake pads wear thin, a special sensor delivers a signal to tell you your pads are due for a change.
Your pads are also fitted with what are known as wear indicators. These thin strips of metal are attached to the pads and will cause a high-pitched squealing sound when the pads get too thin. So if you hear a squeal that sounds like it could shatter a wine glass when you step on the brakes, could be that your brake pads need to be replaced.
If, on the other hand, you hear a grinding noise while braking, chances are you let your brake pads wear down far too much. Now the metal backing on one or more of your pads is coming into contact with a brake rotor. When this occurs, the metal-on-metal scraping is sure to result in damage to the rotor.
If your brake pedal pulsates when you press it, or if your steering wheel shakes when you apply the brakes, those could be further signs that your brake system needs some attention, including new brake pads.
How can you tell if it is time to replace your pads? In a nutshell:
- The low brake pad indicator lamp comes on
- You hear a squealing sound when you press the pedal
- You notice a grinding noise when you brake
- Your brake pedal pulsates or your steering wheel shakes while braking
- Your mechanic inspects your brake system
How are brake pads replaced?
When you take your vehicle in for new brake pads, you can expect that the repair shop will perform a procedure similar to the following.
Lift and support your vehicle off the ground and remove the wheels and tires.
Many auto owners wonder if they can service their own brakes. While the procedure is not altogether complex, there are some inherent risks, including the need to safely lift a four-thousand-pound car.
Disassemble the caliper and remove the old brake pads.
This step requires a technician to take apart the caliper to gain access to the old pads.
Measure the rotors for runout and adequate thickness.
To ensure that the rotors spin true and are in sufficient shape to meet the manufacturer’s specifications, a technician will measure your rotor with special tools. The rotor might be removed and resurfaced, or it might be replaced.
Install new brake pads.
Whether you have chosen organic, semi-metallic, or ceramic pads, the technician will insert the new pads into the caliper bracket, using special anti-seize and anti-squeal materials in the process.
Retract the caliper piston and reinstall the caliper.
The piston inside your caliper will have extended to accommodate the old thin pads. It needs to be retracted to allow the new pads to fit.
Reinstall the wheels and lower the vehicle.
The lug nuts will be torqued to the manufacturer’s specifications to ensure that your wheels do not come off while driving, yet are not too tight so as to keep you from using that tiny wrench in the trunk to remove your wheels in case of emergency.
Perform a test drive to “bed in” the new brake pads.
The new pads (and rotors) need time to wear in together. The technician will make sure they are working properly before you drive away from the shop.
If the brake pads on your bicycle are important, how much more essential are properly-working brake pads on a motor vehicle? If you suspect you need new brake pads, if your car is telling you it is time for a change, schedule an appointment at a trusted repair shop near you. If you are not sure, have a qualified technician take a look. It is best not to neglect the most important safety feature of your car.
Columbia Auto Care & Car Wash | Author: Mike Ales | Copyright October 2019
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