It’s a committee with a noble aim: to rid the streets of inferior aftermarket brake linings. “They’re the Lining Police,” says Dave Embury of the Roadranger Marketing group, referring to the Society of Automotive Engineers Brake Lining Performance Review Committee. The group was formed to take some of the mystery out of making sure the friction level on the replacement lining you choose is the same or equal to the original.
Since there are no government standards for aftermarket linings, it’s easy to spec a replacement that will actually reduce the vehicle’s ability to stop. “It’s not only possible,” Embury told an audience at the Canadian Fleet Maintenance Seminar in Toronto last month, “it happens daily.”
He says the code stamped on the edge of each lining is an unreliable measure of the friction it can provide. Any change in friction level from your original lining spec will make a brake more or less aggressive and may throw an otherwise balanced brake system dangerously out of whack.
So SAE and the Technology & Maintenance Council of the American Trucking Associations developed a procedure for rating aftermarket S-cam brake linings, outlined in TMC’s Recommended Practice 628. The focus is on the torque rating-in this case, represented in inch-pounds at 40 psi brake pressure, which approximates hard braking (most routine stops are less than 25 psi).
The SAE Lining Performance Review Committee has compiled a list of about 60 lining materials, their market brand name, gross axle weight rating, and brake force rating, and requires manufacturers to confirm that each lining has met the brake dynamometer test procedure in U.S. FMVSS 121. Linings can stay on the list for up to five years, at which time they must be retested to make sure performance hasn’t changed.
SAE also conducts random off-the-shelf spot testing of aftermarket linings. This data is compared against the original and if they don’t match up, or fail the FMVSS 121 test, they’re taken off the list.
The committee stresses that qualification of a lining does not constitute SAE approval, and that participation by the manufacturer is voluntary; if a brand is missing doesn’t mean it’s failed FMVSS 121. It may have not yet been submitted to SAE. Another caveat about the list, Embury says, is that it is comprised of S-cam brakes only. That will change, he says, as air disc brakes become more prevalent in the North American commercial vehicle market.