Braking the Sound Barrier: Ceramic Brake Friction Technology

As many in the aftermarket have learned all too well, noise is the single biggest reason for customer complaints. The reality is that this is true in the original equipment market. Noise, not stopping power, consistently comes up more often in discussions of brake friction and rotors than virtually any other topic.

This is, in many ways, a peculiarly North American trait. The European driver, it seems, isn’t so concerned about such aesthetics, but that is just one of the aspects that separates the North American from the European.

“The big difference between Europe and North America is that typically the acid test for brake pad life in North America is L.A. city traffic–to the surprise of no one who has ever had to drive there,” says Bill Hilbrandt, vice-president Research & Development, Akebono Corporation. “For all OE testing, the drive is in L.A. A pad that goes 25,000 miles in L.A. will probably go 60,000 in Toronto. A typical European material will go 8 or 9,000.”

There is also a difference in how aggressive a pad is allowed to be on rotor wear, he says.

“The North American standard is that a brake rotor has to last through at least two sets of pads. In Europe, they change the rotors when they change the pads. That gets to be a pretty expensive proposition.”

There is, of course, another difference. While many European consumers see no problem with having their car’s wheels blackened with brake dust, it is a consequence of brake wear that the North American consumer cannot accept.

It may be hard to believe, but these differences, and the likes and dislikes of the North American driving public, are at the very core of development of ceramic brake friction formulations.

There are a great many formulations that can provide the required stopping power and desirable fade characteristics, but as outlined by Hilbrandt, they may have other characteristics such as a short life, noise, or unsightly dust. This is what ceramic formulations–that first trickled onto the assembly line–were able to combat.

Its addition to the brake aftermarket has been rapidly expanding over the past couple of years, but it was initially received with some uncertainty, says Ian Braunstein, Satisfied Brake Products.

“People didn’t know how to take the ceramics in the marketplace at first. In the industry today it is not one friction fits all. You have to be vehicle-specific. If you put too aggressive a pad on a lower-end vehicle, your installer and your customer are going to have a negative experience.”

Braunstein says that one of the characteristics that sets ceramic formulations apart from other approaches is its forgiving nature.

“Ceramic is a material that can compensate for small deficiencies in the braking system or the job. It is a great DIY material because it is more forgiving, a bit softer, and provides more flexibility in the installation.”

He says that this does not mean that ceramic pads will cure all evils, but there is a bit more latitude before noise and performance considerations become unacceptable.

“A braking system is finely tuned when it comes for the OE, but wear and tear create a scenario where you have unnoticed deviations. Many can be serviced and corrected by the installer, but some things get through.”

There is a limit to what can be compensated for, of course.

Brian Fleming, director of marketing, Dana Brake and Chassis, says that even ceramic formulations can meet their match. “Even ceramics can be noisy if they are used in concert with an inferior rotor. You can get that ringing.”

One thing that everyone agrees on is that ceramic friction materials create less visible dust. They still create dust; it’s just not as visible.

“We say we don’t have dust issues, but if anyone tells you they have a brake pad that doesn’t create dust, they are lying,” says Akebono’s Hilbrandt. “The issue is not whether you create dust or not; the issue is how much you create, what colour it is, and whether it chemically wants to stick to aluminum wheels. That is what defines whether you have an issue. We tend to create very little of it, and what we do create tends to be light in colour and tends not to want to stick to a wheel.”

One other important point is that ceramic formulations are not for every application.

“It is interesting because when ceramics were launched a couple of years ago, everybody was looking at them as the best thing since sliced bread. They’re good brake pads, but in some cases they are not the best,” says Jack McGrail, director of product management, brakes, Robert Bosch. “In heavier applications like half ton and full ton trucks, you would want a semi met. The reason is the heat. A semi met will be able to deal with heat much better than the ceramic.

“It gets into the vehicle-specific nature of the brake system. For light vehicles–Escort, Cavalier, Accord–they work incredibly well. For heavier vehicles, such as Taurus, a semi-met works better. It’s not going to be unsafe, but we have found that the customer is going to be more pleased in the long run.”

With the emergence of the ceramic friction category at the top of the premium brake friction hierarchy, has come the inevitable competitive environment. Brake manufacturers accept this as a fact of life; but competition can take many forms, and not all of them are good.

Some products have appeared on the market with the ceramic name, but without true ceramic formulations.

“The most important thing is that if they put the ceramic name on the box, they can get a premium. Our fear is that there are a lot of inferior products on the market carrying the ceramic name,” says Braunstein.

Akebono calls these pads with a “sprinkling” of ceramic compounds pseudo-ceramics.

“Pseudo-ceramics aren’t great,” says Hilbrandt. “Not all bread is the same. What is a ceramic pad? The definition is quite broad. Ceramics work best when they are combined with other raw materials.”

He uses a brick superimposed on a backing plate to illustrate his point–a brick is a ceramic after all, but would make a lousy brake pad. It isn’t the quantity of ceramic material that determines the quality of the friction, he says. More isn’t necessarily better.

McGrail agrees. “[Developing friction formulations] is easier said than done. Ceramics are pretty complex. It takes a lot of testing to get it exactly right. It’s not just about sprinkling a little ceramic in the compound and letting ‘er rip.

“I think people are trying to do it the right way, but it is tough. From our own experience, we have worked very hard to get our ceramic formula as quiet and dust-free as possible and it is not easy.” Partly this is due to the complexity of the materials, and partly it is due to the fact that it is relatively new to the aftermarket. “It is not like the semi-met we have been working with for 25 years,” he adds.

But some of the old rules still apply: quality costs money.

“But most people don’t know until they put it onto a vehicle,” says Fleming. “Usually you get what you pay for.” He advises asking manufacturers for test data on their products. All reputable brake suppliers will have reports, though for many those engineering reports will be hard to dissect. He has another suggestion.

“If a jobber or service provider is really being honest with themselves, they know where brake manufacturers’ products are positioned.

“Ceramic is the newest formulation, and whether it is new brake material or a DVD player, when it is brought into the marketplace we all pay a premium, but eventually it becomes an everyday product and the price comes down,” says Fleming.

“But to think that you can take the price down to where you’re not paying for it, well, you have to question what you are receiving.”

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BRAKE TESTING AND STANDARDS IMPROVING

While there remain no official government-mandated standards for aftermarket brakes in North America, the development over the past few years of private sector testing has improved both the regimen and confidence in products.

For decades there have been testing procedures outlined in the Society o
f Automotive Engineers standards, but they lacked traceability to the vehicle brake performance tests mandated in vehicle safety standards that all new vehicles must meet.

The two brake dyno testing regimens that have been developed to address this are known as Dual Dynamometer Differential Effectiveness Analysis (D3EA) and Brake Effectiveness Evaluation Procedure or BEEP.

The first is a proprietary private sector test procedure that employs both front and rear brake dyno testing simultaneously. The second, BEEP, is really the marketing identity of the SAE J2430 single brake dyno test method that has been endorsed by the Brake Manufacturers Council of the Motor Equipment Manufacturers Association. Both use brake dyno testing to simulate real-world performance, against federal motor vehicle brake standards as required of vehicle manufacturers–Canadian Motor Vehicle Safety Standard (CMVSS)105 or the newer 135 standard to be exact. D3EA testing is traditionally more expensive than the BEEP test, but both are only a fraction of the cost of whole vehicle testing.

“Having those in place is a massive improvement over what had existed prior to them,” says Akebono’s Hilbrandt. “They have different criteria and different levels of acceptance [in the industry]. Perhaps the one differentiator between them is that the BEEP standard was developed by an industry group and is out in the public domain. I can go get a test schedule and replicate it.

“For D3EA I can’t because it is proprietary. So it is less well known how well it replicates the situation out there in the field than the BEEP test.”

He says that testing is done for either program, depending on the customer’s wishes. “But we view those only as the final confirmation. The internal testing that we do before we would ever run something on a BEEP test is far in excess of what it is going to see on the BEEP test. We have never failed a BEEP test, because we know that stuff is going to work.”

“I think that BEEP is long overdue. It has been a little slow to take off but it is a very valuable tool for aftermarket companies,” says McGrail at Robert Bosch. “The reason is that when there is a lack of any standard it is good to have a standard.”

He says that BEEP and D3EA are both good faith efforts.

“It is not the same as testing on a vehicle, but it is a way to show that your product does do a good job.”

Ian Braunstein, Satisfied Brake Products, says that testing has two effects–it ensures the quality of brake friction from any given manufacturer, and it builds confidence in the aftermarket’s abilities.

As one of two manufacturers dedicated to D3EA testing, the other being Dana, he is convinced of the need to reinforce confidence in the aftermarket. He characterizes some brake products at the low end of the aftermarket as “pathetic and dangerous.”

“We want responsible brakes out there. We in the aftermarket have a responsibility to create these standards.”