Print

Email

Brake Review 1999: Vibration And Harshness Seem To Have Moved To The Head Of The Issues Line

By Tom Glover

A year ago, we described the term "application specific" as the buzzword of the aftermarket brake business. It was, and still is an important issue, brought about by the end of the "one friction material fits all" concept and awareness of how brakes perform in different vehicle designs, plus advances in testing methods.

While application specific formulations are still a hot topic, noise, vibration and harshness (NVH) seem to have moved to the head of the issues line. Shim material topics were paramount on the agenda at the 1999 APRA Brake Clinic held in Los Angeles, CA, recently, and friction suppliers are introducing new low-metallic formulas this year aimed specifically at the NVH problem.

"There’s more emphasis on NVH today than there ever has been," observed Larry Pavey, president of Brake Parts, Inc., now a division of Dana Brake and Chassis. "Trying to maintain customer satisfaction in an aftermarket environment is probably as difficult today, with the aging of the vehicles and the variety of materials that are being used, as it ever has been," he added.

Pavey said that Brake Parts, Inc., will introduce a new, non-ferrous carbon ceramic material within the next couple of months that’s aimed directly at NVH problems. "It’s very quiet, environmentally friendly, and it reduces dusting to almost nothing," Pavey said, adding that of course, it has good wear characteristics.

Performance Friction Corporation in Clover, SC, makes friction materials and integrally molded pads. Rob Nelson, the company’s vice president, studies brake quality reports from J.D. Powers which reveal that brake noise is a great frustration to the consumer. "There’s a significant portion of new vehicle owners who are very disappointed with brake noise, so as an aftermarket supplier, we have to be careful to optimize the material," Nelson said. "We thermally and mechanically attach many of the shims here for both OE and aftermarket applications, all focused on NVH," he said.

Of course shims won’t do much for vibration and harshness, but they do a lot to reduce noise, especially the squeaks and squeals created when friction materials are pushed against spinning disks.

Walt Britland, marketing director for friction products at Federal-Mogul, is quick to point out that while shims are the number one line of defense in reducing brake noise, friction materials are not the only things that make brakes noisy.

"The whole brake system is a factor in setting up vibrations that can lead to brake noises," Britland said. "This is proven by the fact that changing pads or pad materials often doesn’t stop brake noise."

The shims being used today are high tech compared to the devices used to dampen sounds in the early years of disk brakes. Even the name of one of the popular shim technologies, constrained layer damping, signifies that material is more than the rubber or paper used in years past.

Greg Pardus, director of business development at MSC Laminates and Composites in Elk Grove Village, IL, explained that constrained layer damping was developed for the aerospace industry to cut down on vibrations set up in airplane wings and control surfaces without adding significant weight.

"We take two layers of metal and put a visco-elastic between them," explained Pardus. "The metal layers move at different rates, and this micro-movement causes a shearing of the visco-elastic, which absorbs the vibrational energy and reduces or dampens the noise." Pardus also said that the visco-elastic material is only a thousandth of an inch thick. The shim material is attached to the backside of backing plates, most often with a pressure sensitive adhesive.

Obviously the shims and the friction materials themselves are subject to tremendous shear forces that try to tear off or delaminate anything attached to the backing plate. The success of integrally molded friction materials has led some suppliers, such as Federal-Mogul, which now owns the Wagner brand, to use a similar technique in attaching shims. The result is a brake pad with friction material integrally molded to one side of it and a shim, or more properly an insulation material, integrally molded to the other.

When the OE makes pads, they often use shim material that’s configured with tabs that fit inside of integrally molded holes, producing an interlocking mechanism. But the rebuilder doesn’t have it so easy. Most don’t have the space or capital to carry an inventory of precut shim material to fit the hundreds of backing plate configurations out there today.

This is where the drift-lock shim from Anstro Manufacturing Co. of Wolcott, CT, comes in.

Rick Bochicchio, Anstro’s director of engineering and product development, explained that by placing "dimples" or depressions at strategic locations on the shim material, a single configuration of shim will interlock with a number of different plate configurations. "The idea is to have something for the aftermarket people that is cost effective, and doesn’t require a lot of customization of tooling," said Bochicchio. "We can cover approximately 200 applications with 60 shim designs. That allows our customers to minimize their inventories."

Paul Shuck, president of Cleveland, OH, caliper rebuilder Undercar Express doesn’t underestimate the importance of NVH, but thinks that a lot of such issues can be solved, at least in aftermarket situations, with the high quality "loaded" calipers that his company assembles and sells. "If you assemble the caliper and hardware correctly, and lubricate it properly, the chance of noise is greatly reduced," he said.

Schuck thinks that better service life on friction materials is perhaps a more important issue. "Consumers continually want more. They want their brakes to be quite good of course, and they want them to last 40,000 miles, which is why application specific is kind of a given." Adding to his argument, he pointed out that a car owner could be looking at a $1,000 bill if he gets new brakes at all four wheels on his Chevy Lumina. "It’s not getting any better, and people just can’t afford that when the pads aren’t lasting more than 25,000-30,000 miles," he said. "So people will want their brakes to last 30,000-40,000 miles."

Right behind application friction material issues, and related to it are testing procedures for aftermarket brakes. Safety standards for friction materials on new cars has been around for many years. Currently, that standard is known as FMVSS 135, which recently updated the old FMVSS 105 so that it agrees with the European standard. The fact that no safety standards have been established for aftermarket brake friction materials seems ironic, especially when one considers that other aftermarket products such as tires, window glass, certain lighting components and even brake hoses and fluids are mandated to meet the same standards as components supplied on new cars.

This is not to say that aftermarket brakes are unsafe. If they were, lawsuits would be a lot more prevalent than they already are. While many in the industry say they will feel more comfortable when testing procedures are established so that standards for aftermarket friction materials can be specified, not all agree that it’s a necessity.

Walt Britland at Federal-Mogul pointed out that the National Highway Traffic Safety Association (NHTSA) has looked at the aftermarket brake products with an eye toward some regulation, but has chosen at this point not to insist on regulations. "I think they’re satisfied that the industry is taking the initiative to put in place procedures that may help to weed out materials that are not up to par," said Britland. "So right now, I think those voluntary things are keeping regulations in abeyance." In his view, the need for rule making will come about only if there’s a dramatic increase in certain issues, such as safety, associated with aftermarket brake products.

Meanwhile, testing of friction materials using procedures identified as SAE J-2430 has been going on vigorously at the Brake Manufacturing Council (BMC), a trade group of people representing various segments of the aftermarket brake business. SAE J-2430 is known as a recommended practice, rather than a safety standard. It involves a highly sophisticated dynamometer test that takes into consideration different size brakes, as well as the ratio between how much work is being done by front and rear brakes for various car models and/or manufacturer’s platforms.

"During the past year we’ve run tests on five different platforms of cars, where we’ve tested various materials using the J-2430 procedure. "We’ve compared the data on the results to the current motor vehicle safety standard FMVSS-135," said Jim Lawrence, the director of the BMC organization.

"Of course the key to having the standards accepted is the repeatability of results," he said. "What has to happen before we can establish standards is that enough people have to run dynamometer tests using their own testing equipment and staffs, and get repeatability and accuracy." Lawrence hopes that by the time the BMC meets in Toronto in late August, enough people will have run the tests using the J-2430 procedures that the results can be brought to the table to establish a good incidence of repeatability, and progress toward the eventual establishment of standards can be made.

Part number proliferation is always an issue in the automotive rebuilding business, but many in the brake aftermarket segment have the perception that it’s leveling off. However, the numbers, at least for the past year, tell a different story.

According to Gil Laycock, director of the Friction Materials Standard Institute (FMSI), his organization published it’s 1999 catalog with 123 new brake part numbers assigned, covering six different categories of parts. Disc brake application assignments accounted for 52 of them. The year before, there were only 67 total new parts, 26 of them disc brake parts.

"Part number proliferation is one of the biggest things I have to deal with," said Bill Bosch, an executive vice president at General Brake, Inc., Arkadelphia AK. In his view, it’s largely unnecessary. "It has to be costing OEMs money, and it makes everybody else spend money keeping up with it," he said. "I do sell a few more sets, but it costs me to sell them, so it’s probably a wash."

Several sources cited that the OEMs seem to have settled on changing brake systems for new platforms of cars on a three-year cycle, which at least gives rebuilders a chance to keep up. "Actually, the OEMs are changing things faster in the truck and light truck end of the market than they are for passenger cars," said Tom Moalli, vice president of Tek-Motive, Inc., East Haven, CT. "You’re seeing in the light truck market now what you’ve seen in the automotive market in the past."

One of the things that Moalli is referring to is the greater use of disc brakes at all four wheels of light duty trucks, which are typically rear wheel drive vehicles. "The new GM Sierra and Silverado have disc brakes all the way around, and Ford has some heavier trucks that are all disc too," he observed.

For decades, perhaps ever since disc brakes became the standard system for front wheel drive vehicles, people in the brake business have been saying that the days of the drum brake are numbered. But for a number of reasons, probably cost and weight being the most important, drums and shoes have hung around a lot longer than many expected them to.

"It’s made a lot of us experts look foolish, because our predictions have gone awry," said Larry Pavey of Brake Parts, Inc. "For many years, we were looking for the decline of brake shoes and segments, but we’ve actually had to reverse and do some investment in those businesses because there’s been good growth in it, based on the popularity of SUVs and pickup trucks," he said.

But there’s a reason for everything, as the saying goes, and many believe that practicality is behind the fact that drum brakes have hung around all these years. "Disc brakes on the front was a smart idea, but disc brakes on the rear is only smart in certain applications," commented rebuilder Bill Brosh of General Brake.

"A Corvette will take advantage of rear disc brakes, but on a four-cylinder Neon, there’s no need for them," he said. "They cost more, and they would actually do too good a job, so they have to be engineered to work less optimally than they normally would. To me, going to four-wheel disc brakes is a marketing thing that has nothing to do with function."

With the SUVs and pickup trucks going to discs on the rears, however, perhaps the often-predicted end of drum brakes has accelerated up a notch. However, people we talked to were not about to count them out in the near future. "I think you’ll always have drum brakes, but the higher end rear wheel drive vehicles will migrate to discs at all four wheels," said Shuck of Undercar Express, adding that GM has broken a barrier by going to a phenolic brake piston for the first time in history on its CNK pickups for model year 2000.

Distribution changes
The changes in the distribution channels in the aftermarket brake business continues along the two-step track, where rebuilders sell to warehouses who sell to installers. "The change to the two step system was made 10 years ago, and it’s stayed pretty much the same since," observed Brosh of General Brake.

On the other hand, Britland of Federal-Mogul observed that the three-step system can and does survive when jobbers can offer what he calls a "value added" package. An example would be where a jobber can offer some product differentiation that is not available from retailers, such as a more comprehensive stock of parts and delivery services.

In the opinion of many, the elimination of the jobbers in the distribution system has happened for the same reason that a number of small rebuilders have declined over the last few years. Very simply, in many cases the cost of equipping and operating a shop has gone beyond what independent entrepreneurs can handle.

"Most brake rebuilding shops are owned by somebody else now, either directly or indirectly," observed Brosh. "It’s a big investment to do what we do, and it gets harder and harder. If you don’t stay on your toes all the time, you’re not going to make it."

General Brakes assembles rebuilt brakes using Bendix friction material exclusively, and Brosh pointed to his situation as an example. "Even though I own my own business, I’m building somebody else’s brand, so in some ways, I’m in the same boat as everybody else."

Looking at the future of automotive brakes, some see a move to the use of cryogenics to fashion new brake parts and friction materials that are stronger and more durable. Others, such as Walt Britland of Federal-Mogul, reported that R & D labs are exploring alternatives to ferrous materials for the opposing surfaces of brake parts.

Meanwhile, you can be sure that the issues that have dogged this industry for a number of years - NVH, application specific friction materials, parts proliferation and performance testing standards, plus the decline in the number of small rebuilders, will probably be with us for awhile longer. Meanwhile the brake rebuilding industry will continue to work on these issues, and find remedies.