LAS VEGAS — Just about anyone who works in the auto repair business would agree that the brake friction market has changed dramatically in the last couple of decades.
“The way we repaired cars 15 or 20 years ago is a lot different from what we do today, and the brake side of the business is changing tremendously,” noted Walter Marciniak, director of technical services for Brake Parts Inc. (BPI). “It's tying into chassis dynamics—we got cars braking themselves. We got cars parking themselves....but everything seems to tie into the brakes.”
During a seminar at last year's AAPEX show in Las Vegas, Mr. Marciniak and Dann Ingebritson, BPI technical trainer, outlined how brake pads and related parts have evolved in recent years to meet changing vehicle technologies.
In the good ol' days, asbestos was the material of choice for brake pads — before scientists realized the material posed a health hazard to humans, prompting the material to be banned from all sorts of products.
Unfortunately for the automotive industry, asbestos, which was “soft and forgiving,” remains the best type of friction material, according to Mr. Ingebritson. Materials used today are “totally different.”
Friction materials today are classified in three categories: semi-metallic, ceramics and non-asbestos organic (NAO).
BPI hasn't used asbestos in its brake pads for about 15 years; however there are manufacturers in other countries that still use asbestos, he said.
“If you're garage owners or technicians, you have a huge choice to choose from, and the thing is if you stay with a manufacturer that manufactures (the brake pads), you know exactly what comes in the box.
“If you buy from a person — like the guy who pulls up to your shop with the white van and no name on it — and he sells you this product that's pretty cheap and it's in a white box — and it works! I hear this all the time: 'Man, that stuff works and it's only 18 bucks.' I can almost guarantee that there's asbestos in that product. If it's that good, it probably has asbestos. So watch out where you buy from,” Mr. Ingebritson warned.
In the 1970s semi-metallic brake pads began replacing pads made with asbestos. While these new products stopped the car effectively, they would leave the then-popular white wall on tires black, Mr. Marciniak noted.
To solve this problem, ceramic brake pads hit the market in the mid-1980s, but they created their own set of headaches, including pedal pulsation and copper dust.
“Now we're in another evolution. We're in the copper laws,” he said,
“We put copper in a ceramic for a couple of reasons. One is to scrape that rotor to keep that material smooth. It also pulls heat out.... We need something abrasive to keep that ceramic material nice and smooth on the rotor,” he said.
However, the California and Washington legislatures are requiring friction-materials manufacturers to reduce the amount of copper used in their brake pads. They claim the copper-infused dust that comes off brake pads during braking on roads and highways is polluting the waterways and harming wildlife.
Both states forbid the sale of brake pads containing more than 5 percent copper starting in 2021. California will ban brake pads containing more than 0.5 percent copper as of 2025.
Some manufacturers already have introduced products that meet the 2021 and 2025 requirements. Semi-metallic pads don't usually contain copper, according to Mr. Ingebritson. “It's a struggle (with ceramic pads) on what to use besides copper.”
“So we're going to see another phase of brake pads coming in soon where there's going to be a combination of ceramic and metallics — hybrid pads. It's always an evolution,” Mr. Marciniak said.
“Unfortunately, as we have these evolutions sometimes we, as installers or as technicians, have to kind of suffer with the program. It's a big headache.”
He noted that since the 1980s, technicians have had to deal with a different set of braking complaints.
“Prior to 1985 did we have pedal pulsation like we have today?” he asked. “It seems like we have a lot more pedal pulsation. The dynamics of the vehicle have changed. We've gone from big hub rotors with wheel bearings to slide-on rotors going on hubs.”
“Ceramics are totally different from semi-met pads. Semi-met pads stop with what they call abrasive stopping. Your brake pad is wearing against that rotor. So when you stop, you are metal against metal basically,” Mr. Ingebritson said.
“Ceramics are totally different. Ceramics have what they call adhesive stopping. So there is ceramic material that the pad leaves on the rotor. Every time you stop, it coats that rotor. It's called material transfer. So, that material should be layered really nicely on your brake rotor.”
Ceramics run hot — leaving hot spots on the rotor, which is friction material. The reasons the material gets bunched up in one area is because the rotor has too much runout, he noted.
“So the rotors are wobbling back and forth and kissing that pad every revolution and that's what's causing that to all build up in one spot. And guess what that causes when you hit the brake pedal after a couple of months of that? Pedal pulsation.”
He said techs shouldn't use the term “warped rotor” because the rotor really isn't warped; it has thickness variation.
“That is our biggest problem out in the field is between brake noise and this pedal pulsation. So your ceramic brake pads are really to the point where they will cause that rotor to have that issue when the rotor is not running true.”
In the “old days” when a rotor had runout, it didn't matter because asbestos pads were soft and would bend into the rotor, Mr. Ingebritson said. The rotor wobbled back and forth but the caliper absorbed the vibration.
“So we never had to worry about rotor runout back in the '90s.”
The stiffer brake pad materials of today accentuate the runout issue.
“If you allow too much rotor runout when you install that rotor, with every revolution that rotor will come around and kiss the pad in that same spot over and over again.... Ceramic brake pads leave material on the rotor; semi-mets take material off the rotor,” he said.
“When your pads clamp down on the rotor, if the rotor was wobbling back and forth, the whole caliper wobbles with it. You don't feel the pulsation. But when that rotor gets thicker or thinner in one spot, and (the brake pad) clamps down on it and the pads go out-in, out-in; the piston's going out-in, out-in.
“That's what you're feeling in your brake pedal. You're not feeling a warped rotor. You're feeling thickness variation of the rotor caused by excessive runout when you installed the rotor,” Mr. Ingebritson said.
Like brake pads, rotors have evolved over the past 10 years. Manufacturers have changed the metallurgies, vane configurations and coatings on rotors.
Rotors help dampen vibrations and limit brake noise. This is the reason for the multitude of vane patterns and the use of damped iron in many rotor applications, according to Messrs. Ingebritson and Marciniak. They noted that allowable rotor runout used to be 0.01-inch. Now it's 0.002-inch or less.
“When you pull that brake rotor off, you've got to make sure to clean rust out of the hub area,” Mr. Marciniak instructed. “We see a lot people who don't pay attention to that. They figure: 'The rust is kind of smooth so I'll just put it on the car and crank it down with lug nuts.'
“The trouble is, a piece of rust in the wrong area can add 0.015-inch to the runout.”
“If you clean the hub and put the rotor on, you got about an eight out of 10 chance of it never coming back to haunt you because you did a good job cleaning the hub. But if you don't do a good job cleaning the hub, you're going to have excessive runout,” Mr. Ingebritson warned, adding: “Do it right or don't do it at all.... You have to clean the hub. There's no if, ands or buts — you've got to clean the hub.”
After cleaning the hub, technicians should check the runout.
“If you're not checking runout and you're dealing with these vehicles with pedal pulsation coming back in two to three to four thousand miles, you got to think seriously about checking lateral runout,” he said.
Techs need to install all the lug nuts on the hub before checking runout, Mr. Ingebritson said. Then they should use a dial indicator to measure runout and match to vehicle specs, which typically range from 0.002 to 0.004-inch.
If the rotor has about 0.005-inch runout, try indexing the rotor to the hub, he said.
A runout of 0.002-inch is the most common; premium rotors have at most 0.001-inch runout.
“We've been asked, 'Why don't you make a perfect rotor?' And I say, 'We do. But we sell them to NASCAR. They give us thousands of dollars for them,'” Mr. Ingebritson quipped.
The rotors typically worked on in auto repair shops will commonly have a 0.002-inch runout.
If a vehicle has a hub with 0.003-inch runout and the rotor has 0.002-inch runout, that totals 0.005. Mr. Ingebritson suggested techs take the rotor off and turn it 180 degrees and put it back on.
“You might nail it down to zero or 1/1000ths runout within specs — that's called indexing the rotor to the hub,” he said, likening it to balancing a tire.
“One of the biggest excuses we hear when we go out to the shops is, 'I don't have time to do that,' Mr. Marciniak said. “What's a comeback cost you?”
To reach this reporter: [email protected]; 330-865-6127; Twitter: @kmccarr