Take a good look at the magazine in your hands. Once you finish studying the ads and articles, you could take the pages, combine them with some mounting hardware and re-sell them as a brake lining. It’s an absurd example, but it illustrates a significant gap in the regulations that govern aftermarket friction material.
To be specific, there are no rules.
“It is an issue,” notes Alan Hendershot, test manager for Bendix-Spicer Foundation Brakes. Vehicle brakes need to meet the stopping requirements of Federal Motor Vehicle Safety Standard (FMVSS) 121 when a truck first leaves the factory, but the rules don’t extend to a trailer load of brakes that the truck might be asked to deliver. “There are very low-performing friction materials being sold in the aftermarket,” he says.
“A lot of it is very, very bad. It’s to the point of being dangerous,” agrees Randy Petresh, Haldex vice president – technical services. Then again, it is hard to tell just how bad it is. The products often disintegrate before Haldex engineers can complete a traditional battery of tests.
To compound matters, the existing markings offer little insight into the stopping power of different components. Edge codes printed on the friction material – in the form of something like an “FF” or “GG” – represent different things to different manufacturers.
“That code always was meant to be a quality control measure in the manufacturing facility. It’s not a good predictor or indicator of the performance of the material,” Petresh explains. “Some states require it, but it’s really of no value.”
Any reference to the coefficient of friction is largely a measure of the consistency of the material, but it does not offer any insight into factors such as lining life, drum wear or other characteristics, adds Carl Swanson, aftermarket brake product manager for Bendix. And information such as the Friction Material Standards Institute (FMSI) number or drill-hole pattern merely will ensure that the product will fit in place.
One of the few sources of comparative information comes in the form of Technology & Maintenance Council Recommended Practice 628 (TMC RP 628). That chart identifies the torque delivered during a 40-psi brake application.