Publisher's Note: Welcome to our 29th edition of Tech Tips Tuesday on "Brake Pedal Pulsation Demystified: Causes and Cures".  We'll be re-publishing an edition of AMSOIL Tech Tips for you every Tuesday.  Click on the Blog Category "AMSOIL" to see everything published to-date.

Brake Pedal Pulsation Demystified: Causes and Cures

John Gardner: Have you ever brought your vehicle to a stop and you feel the brake pedal going up and down, or even the steering wheel shimmy? Well, what is it and how do we solve that problem of brake pedal pulsation?

Welcome to this AMSOIL Tech Tip. What you probably have is a brake pedal pulsation. Now, what causes it? You can actually see it here on the graphic. Matter of fact, I can demonstrate it right here. Our rotor, you could have what's called lateral run-out, which means the rotor's warped, and as it's warped, it's going around, and when it goes around, it's actually touching that pad every time in the same spot.

Now, that's really not causing the pedal pulsation, but what that causes is disc thickness variation (DTV). What does that mean? Well, that's in and out of the rotor where it's been eaten at in places. It doesn't have to be lateral run-out, doesn't have to be warped, but it goes in and out. So, when it goes in and out, those pads are squeezing, and you're feeling that come back into the actual pedal.

Now, how do we check for that? Well, it's real simple. You can get a dial indicator. We just secured the hub to the rotor. Once we did that, we put a dial indicator on it, spun it around. Manufacturers usually don't want more than about three-thousandths disc thickness variation. You can take a micrometer and go in eight places around that rotor. You don't want more than a half of a thousandth; that's going to cause pedal pulsation.

Now, once that happens, Len, I got to either cut the rotors or throw them out. That's costly. How can we avoid it?

Len Groom: Well, you want to start by making sure that there's no rust on anything. So, if you've got issues with your hub, get a good look at it. If you need to clean some rust off there, you go ahead and wire brush that right off there. Make sure you hit it with a little brake clean, clean anything off there. Make sure your surfaces are flat.

John Gardner: Yeah, and that's a new term out there called stack tolerances. We want to make sure that's on there and on there right. Another thing, no place for gunplay putting on wheels. Do not use an impact. Use your torque wrench or torque sticks to put it on.

Now Len, these rotors, they come out. Once we're done with that job, we want to make sure they're clean. This one actually came from the factory, and you can see this stuff. There's a coating on there. You guys got a product that takes care of that and so much more.

Len Groom: Yep, you want to make sure that you clean that off really well. You want some good pressure in the can, a real good solvent product that dries really quickly. So, you just go ahead and hit that. We got a little all over.

John Gardner: Yeah

Len Groom: And it'll clean that right off real nicely.

John Gardner: Did that in no time.