Opinion: New Stopping Distances, New Technology
By James Clark
Director of Engineering
TMD Friction Inc.
This Opinion piece appears in the April 23 print edition of Transport Topics. Click here to subscribe today.
I’m proud to be a member of the North American heavy-truck supplier community. Together, we’ve made significant strides in Class 8 truck brake safety, but not since the introduction of non-asbestos brake linings more than 20 years ago has the heavy-duty industry seen technological changes to brakes as significant as those we are experiencing today.
Two new products in particular — high-torque drum brakes for the new reduced stopping distance regulations and air disc brakes — have hit U.S. roads recently, and that means it’s no longer “business as usual” when it comes to selecting replacement linings. Every maintenance manager needs to understand these new technologies and to know how to make sure he or she has the information needed to avoid costly mistakes in selecting replacements.
Over the years, we’ve seen the development of brake-related technologies ranging from automatic slack adjusters to anti-lock braking systems. In the normal way of things, new technologies are introduced to the market by safety-conscious suppliers, safety-conscious truck manufacturers and safety-conscious fleets. Once they have proved reliable, standards are established and regulations created.
That’s where we are now with aftermarket brake linings — fleets are using them, but we lack regulations to standardize and control their performance. That means there are no effective safeguards to ensure that an aftermarket lining can stop a Class 8 vehicle within the same distance as the original-equipment linings.
A new truck’s brakes must pass two legal requirements as defined by Federal Motor Carrier Safety Standard No. 121 — a brake dynamometer certification and a full-vehicle stopping-distance test. This regulation includes torque output performance, fade and recovery characteristics and fully loaded stopping distance tests from 60 mph.
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