A brake pulsation is the vibration effect that you get from pressing down on the brakes for too long. This effect is often a sign of friction and heat that often comes from two mechanical components pressing down on each other. The best way to tell which rotor and brake pad are causing the pulsation effect is by holding down the brakes and feeling the vibration.
Signs and Indication of a Brake Problem
If you feel that the vibration is generated on the steering wheel, then this means that the fault is stemming in the front rotor and pad. However, if you notice that the pulsating or surging vibration is felt more in the seat or rear end, then a rear rotor and pad are likely causing it.
Reputation of Brake Pad Formulations
Ceramic pad has the reputation of being very quiet and also have a reduced rotor wear. On the other hand, a semi metallic pad is one that comes with a performance reputation where it can stop a vehicle numerous times and at a very short distance.
As you press on the brakes, it latches on to the rotor, and due to friction and heat, it leaves a transfer layer on the vehicle. Over time, the brake pad loses its pad material and you have to replace it for new ones. This is why it is very important to know about lateral runout and disc thickness variation when you are trying to diagnose brake pads and pulsation.
Lateral Run-out and Disk Thickness Variation
If you have lateral runout on the vehicle, or in other words the rotor is going back and forth, then you will have a high spot of run-out and a low spot of run-out. As the brake rotor goes past the brake pad, it removes a little bit of the rotor over time.
Similarly, it could also be causing the same type of wear on the low spot of the tire. This type of wear removes material from the rotor, and when it is removed, you are ultimately changing the thickness of the rotor. When the thickness of the rotor changes, it exposes the piston inside the caliper every time the spot goes by the brake caliper.
This is what causes brake pedal pulsation. For this reason, a ceramic brake pad is better at controlling the pulsation. One of the reasons why is that it is using a transfer layer, which means that you have lower rates of rotor wear. Moreover, as it passes the high spot, it loses a little material to it. Changes are that the thickness variation is not as great as if you are using a semi matte pad.
No matter what type of brake pad you install on your vehicle, you have to make sure that it matches the OE specifications. More than anything else, make sure that you install it properly. Not to mention, you also have to be careful of the runout and wheel bearing. All of these considerations can be difficult. This is why you must get technical help.