Tech Articles

Ask Away! with Jeff Smith: Should I Grind the Rough Surface Off of New Brake Pads?

change brake pads

(Image/halfords.com)

I’m looking to buy some upgraded brake pads for my 2010 Chevy 1500 pickup as the brake pedal is starting to shudder on even light brake application. I’ve been reading stuff online and one guy mentioned that he’d never buy a particular brake pad again because when he first installed them, the pedal felt weird and it didn’t stop well. He said he had to remove the pads and grind off this rough stuff on the pads that was almost like sandpaper. He said he had to do this twice and then later the pads smelled funny so he trashed them and bought another brand. Now I’m confused because another friend said he should have given the brake pads a chance to work. So who is right?

J.D.

Don’t Brake the Pads

Jeff Smith: As much as things have changed in the world of brake-friction materials, the break-in requirements for new pads have remained the same.

All brake pads intended for the street, regardless of their construction or material, all operate the same way. All brake pads use a process where a portion of the material is transferred from the pad to the surface of the brake rotor. This does not happen instantly—it requires some time and most certainly heat and pressure to ensure this process occurs. This is important because that transfer process increases the friction between the pad and the rotor.

It’s important to know this because after new pads are installed, the installer must perform what is called the bedding-in or bed-in process. Each manufacturer has its own specific requirements, but the approach is mostly the same for all new brakes.

If the rotors are going to be re-used, the ideal bedding-in process demands that the old brake pad material be removed. The brake pad companies know this isn’t always practical and that people rarely do it.

One process uses a separate, highly abrasive set of metallic, pure-race brake pad material for a short amount of time. This material will abrade (lightly machine) the rotor brake surface. As you can imagine—pretty much no one does this.

So to help prepare the old brake rotor surface, many high-quality brake pad manufacturers apply an abrasive to the surface of the pads. See the photo of EBC’s YellowStuff brake pads with an abrasive coating? It looks and feels a lot like sandpaper.

EBC YellowStuff brake pad

(Image/EBC Brakes)

The design uses short-term abrasive friction to cut through the original brake pad coating on the old rotor to prepare the surface for the new brake pad.

Bedding-In Brake Pads and Why It’s Important

Most brake pad bedding processes require about 20 minutes and involve applying the brakes with a gradual increase in pad temperature.

This accomplishes two objectives.

  1. The first is to heat the pads to essentially “cook” the final bonding resins out of the brake pad material. These resins are what hold the different chemicals together until they can cure under high heat.
  2. The second objective is to sufficiently heat the pads to ensure that the pad materials are properly transferred to the disc rotor.

This heating cycle will generally heat the pads hot enough that you will smell the resin as it cooks out of the pad. You may even see a small amount of smoke coming from the pads. This is normal. When the commenter said he removed that abrasive finish from the pads, he wasn’t helping himself. This only means that he would have to perform an aggressive bedding-in process to ensure that transfer of the brake pad material.

Avoid Imprinting Which Causes Brake Shudder

It’s also important once that bedding procedure is complete that the brakes be allowed to completely cool and that you avoid holding the brake pedal down at a stop light for example when the brakes are hot. This can cause what is called imprinting.

Imprinting is caused when the brakes are applied at a full stop while the pads are still hot and can cause the transfer of material to the rotor almost like a decal. This additional material can cause a light raised portion on the rotor that will cause brake shudder, so you’ll want to avoid that.

We referenced several embedding processes and the least-aggressive of these merely suggests that normal driving of 400 to 500 miles will eventually bed the brakes. While this will work, the plus side to performing the more aggressive bed-in process is that once the brakes have completely cooled, the transfer process will be complete and the brakes should perform to 100 percent of their capability. In the normal driving process, the pads have not been fully cured and bedded, so they won’t offer 100 percent of their potential braking efficiency right away.

You should never sand or modify brake pads for several reasons. Some people think that if a set of pads have been glazed, they can just sand them down and they will work fine again.

That’s not true.

Once the pads have been overheated and glazed, they should be replaced.

Sanding brake pads is a bad idea for multiple reasons, a major one being that sanding will push foreign materials into the pad which can cause all kinds of problems.

So our recommendation would be to choose a quality brake pad for your truck, do some comparison shopping and perhaps search around for recommendations from people with personal experience with the pads you are considering. This will help you decide on the brake pads that will best serve your needs.

THEN, do the proper bedding-in process.

With that done, more than likely you will discover the brakes on your truck will perform far beyond than your expectations.

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11 Comments

  1. Also discard any brake shoe/pad that have been contaminated by brake fluid, eg. leaking wheel cylinder,no mater how new they are.

  2. Great article but the last recommendation sounds stupid, as you are professing to know something about brakes yet you tell readers to “ask around for recommendations…” your credibility goes out the window here when you don’t point the reader in the right direction, Can’t you mention a quality brand or some specific types of frictions to buy. I can sum up your whole story in 4 words. “Don’t buy the cheapest brakes you can find… and ask around and I can’t count. People that read How To’s want a list of brands, and prices would be nice 😉 How bout a follow up story?

  3. Carson G. Praefke says:

    Hi Jeff, The initial complaint was about the brakes shuddering. I would recommend the rotors be turned on a lath or replaced at the time the new pads are installed. The rotors are probably warped from overheating or being warn to thin. A micrometer should be used to see if the rotors are still within factory specs. If they are too thin, they should be replaced. Only replacing the pads, even if they are broken in properly, may not solve a brake pulsation.

  4. Great article! cleared up alot of questions I had about brake pads and rotor.
    Thanks!

  5. Howard Elwell says:

    Do most shops that we pay to do a brake job do this “bedding in”?

    • Howard,
      You would have to ask the specific shop, but in most cases I would say probably not. So it’s left to the owner to perform his pad bedding process. This is why I mentioned this in the answer

      • This is NOT true. We test drive the car after brakes are installed and do the bedding process the . it would not be safe to leave that up to the customer so fyi …if you don’t know the answer. Dont content.

  6. I worked for a cadillac garage back in the 70s and we always turned the rotors. now everything is probably remove and replace. if you did a brake job you took a test ride, then parked it. I have seen brake caliper pins that were so worn, no way was equal pressure applied to rotors. I’m old but believe a lot of dealerships and jobbers push their mechanics to much. all about the money. can lead to sloppy work. which leads to shop comebacks.

  7. Hello dude, Thanks for your explanation. It helps me a lot.

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