When Your Brakes Pulse
Youíre driving, and you press on the brakes, only to feel that pulsating sensation. The first diagnosis that comes to mind could be a warped brake rotor. Before going any further, generally speaking, a warped brake rotor means any brake rotor that isnít perfectly flat and parallel with the plane rotation. There are many causes that can lead to a pulsating brake.
One of the most common causes of a warped brake rotor is the improper installation of the wheel. Modern brake rotors are thinner at the friction surface and overall there is less material everywhere. That fact alone makes them vulnerable to warping thanks to both heat and improper lug nut torque. Your service technician should be very well aware of this, and therefore tightens the lug nuts in the correct sequence with a torque wrench.
Take out of the equation that everything is assembled correctly, and then the most common cause of brake pulsation is from the uneven transfer of friction material from the pad to the rotor.
Now there is a situation when youíll feel normal brake pulsation. If your vehicle is equipped with an anti-lock brake system (ABS), and you have to hit the brakes quickly, you will feel a pulsation, but that is completely normal.
Keep in mind that brakes work best when within a specific temperature range, and the friction material that makes up the brake pad is designed with those temperature ranges in mind. A thin layer of friction material from the brake pad adheres to the rotor. This bedding-in process is what makes up this initial layer. The problem arises if the brakes are bedded in when new, or if the pads are severely overheated at any point in time, then that friction material becomes uneven and you can then have that pulsating problem. Should your brake rotors overheat, they can develop heat checks, and unfortunately they canít be resurfaced and your only option is to have them replaced.
Other issues that can cause problems include warped hubs, worn wheel bearings, and CV joints that become stiff. Individually, each of these factors could create rotor problems that would be barely measurable. However, put them all together and youíll know it when you depress your brake pedal.
So, bottom line. Why should you be concerned when you have pedal pulsation? It can be a safety issue since even the mildest pulsation can compromise ABS performance. And if you have to brake quickly, your braking distance is affected which can mean the difference between a fender bender and a serious collision. Braking pulsation also makes your car more difficult to control, and thatís another safety issue. So when you feel that pulsation when youíre braking, itís time to get your car to your service technician to ensure the optimum performance of your carís ability to stop, and most importantly, your own safety.
Johnny Nocera has been on the radio airwaves in Southwest Florida with ďDr. Johnnyís Car ClinicĒ WGUF New Radio 98.9 FM every Saturday morning from 9-10 for over 27 years. He also owns, along with his sons Jr. and Jimmy, Supreme Auto and Collision located in downtown Naples, and has been in business for more than 38 years.