I have always believed that the basic air-brake training drivers receive in pursuit of a CDL overemphasizes the technical/mechanical side of the brake system while doing little to contextualize brakes as drivers experience them from the driver's seat. - Photo: Jim Park

I have always believed that the basic air-brake training drivers receive in pursuit of a CDL overemphasizes the technical/mechanical side of the brake system while doing little to contextualize brakes as drivers experience them from the driver's seat.

Photo: Jim Park

Drivers are an integral link in the brake maintenance chain and thus the vehicle safety chain. They are hands-on with the equipment every day, while shop staff see trucks very much less frequently. Drivers see, hear, and feel the trucks in action, while technicians see only a static component. Do your drivers know enough about brake systems to help maintenance staff identify defective equipment?

Brakes pose an interesting diagnostic and maintenance challenge. On the whole, modern brake systems, drum or disk, operate reliably and trouble-free for hundreds of thousands of miles, so the de facto condition of brakes is good-to-go. On top of that, brakes are seldom stressed under normal operating conditions, so any underlying problems may never be detected. With engine brakes as effective as they are, brake applications above 20 or 30 psi are uncommon, yet it's at higher application pressure that problems can become more obvious.

Take brakes that pull to the right or left, for example. Drivers wouldn't notice a pull at low application pressures, but if a problem existed, they surely would notice something at 40 or 50 psi application pressure. There are several possible culprits for a pulling condition:

  • One or more brakes may be out of adjustment.
  • Brake clevis pins could be seized, inhibiting push-rod movement.
  • Cam bushings could be seized or damaged, inhibiting rotation of the cam rod.
  • Brake linings could be contaminated with oil caused by a failed wheel seal.
  • Brake chamber push rods cut to the wrong length could be hanging up on the mounting brackets, inhibiting travel.
  • Brake relay valves may be delivering unequal air pressure or volume to different wheel-ends.
  • Air lines that aren't matched to brake chamber type, or a restricted or leaking air line, could cause unequal air pressure or air volume to the brake chamber.

How would a driver know to report such a condition to the maintenance department if he or she had never experienced a symptom? Yet I'm sure you'd agree any of those conditions could be present on any number of your trucks.

Some cases where a truck pulls to one side or another may not be brake-related at all. Failed or worn suspension bushings will cause a temporary misalignment of the steer or drive axles when the brakes are applied, causing the unit to pull right or left.

A thorough visual inspection of the type performed by roadside inspectors during events like Brake Safety Week or Roadcheck would uncover some of those problems, but not all.

Are the Basics Enough?

I have always believed that the basic air-brake training drivers receive in pursuit of a CDL overemphasizes the technical/mechanical side of the brake system while doing little to contextualize brakes as drivers experience them from the driver's seat. 

What's really more important in day-to-day operation: being able to point out on a schematic diagram which valves are relay valves, or what it feels like when the tractor brakes apply sooner than the trailer brakes? 

In terms of their potential for calamity, which scenario would be worse: brake linings worn thin and close to the legal limit, or nice thick linings that never wear down because they are so hard and have a very low coefficient of friction? I've driven with such linings; they will last forever, but they hardly stop the truck. Would a rookie driver know the difference between hard linings and brakes that had gone beyond their adjustment limit? They feel about the same. 

Given the number of brake violations uncovered at various organized inspection blitzes, I hardly think drivers are doing a good job at keeping ahead of the problems. 

It's a near certainty that few drivers do mark-and-measure inspections every morning. They probably don't need to go that far every day, but cheap and easy-to-install brake stroke indicators would help turn the mark-and-measure inspection into a one-knee inspection where a driver could conveniently visually verify that the brakes are still reasonably close to being in proper adjustment. 

But how many drivers would understand the difference between spring-applied brake stroke and an application of between 90 and 100 psi? Drivers need to be aware that the difference between the two could be upwards of half an inch of stroke length. If it's near the limit with the parking brakes applied, it will almost certainly be over when checked under full application pressure by a CVSA inspector at roadside. 

How much coaching and brake update training do you offer your drivers? 

Most of them are not mechanics or engineers, and they probably don't need to understand schematic diagrams, but it would sure be useful to get a few reminders in the company newsletter on how to inspect brakes on one knee or how to interpret a pulling sensation in the steering wheel when the brakes are applied.

How about a reminder of how to apply brakes when the ABS isn't working (ever noticed black electrical tape covering the dashboard ABS lamp)? 

I'd bet that few drivers really understand their brake system in a practical sense. And if you think they are likely to have retained much of what they learned in CDL school two, five, or 10 years ago, you're fooling yourself. 

If you're thinking that a brake refresher course for drivers might be a good thing, ask yourself, are we doing it to pass brake inspections or to improve road safety? That might inform what you decide to offer them.    

Author

Jim Park
Jim Park

Equipment Contributing Editor

A truck driver and owner-operator for 20 years before becoming a trucking journalist, Jim Park maintains his commercial driver’s license and brings a real-world perspective to Test Drives, as well as to features about equipment spec’ing and trends, maintenance and drivers. His Ultimate Test Drive and other videos bring a new dimension to his trucking reporting. He is the host of HDT Talks Trucking podcast.

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A truck driver and owner-operator for 20 years before becoming a trucking journalist, Jim Park maintains his commercial driver’s license and brings a real-world perspective to Test Drives, as well as to features about equipment spec’ing and trends, maintenance and drivers. His Ultimate Test Drive and other videos bring a new dimension to his trucking reporting. He is the host of HDT Talks Trucking podcast.

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