Don’t ignore ABS maintenance

Unfortunately, many fleets neglect their antilock braking systems because they are aren’t inspected at the roadside, says brake expert Richard Radlinski. DOT regs don’t even require that ABS installed prior to new equipment installation mandates be operating. But Radlinski, head of Radlinski and Associates Inc., is helping the Commercial Vehicle Safety Alliance develop a standard for ABS roadside inspections. With someone like Radlinski advocating inspections, we just might see them before long.

“Without enforcement, there’s little incentive to keep [ABS] maintained,” Radlinski told attendees at the recent Commercial Vehicle Safety Alliance Workshop in Rapid City, S.D. That neglect is unwise, he says, adding that ABS should be an integral part of truck maintenance and inspections.

Radlinski, who delivered a presentation to CVSA’s driver committee on developing a standard and on training officers to check ABS function at roadside, is hardly a disinterested bystander. As a federal official in Washington, he advocated truck ABS. But Radlinski is not your typical paper-pushing bureaucrat. He is known widely as a bright and creative engineer who loves trucks and will never open his mouth until he has done his homework.

Most fleet owners know that ABS helps prevent tractor-trailer jackknifing and allows a driver to steer around an object even under hard braking. Few seem to realize, however, that ABS was also adopted to shorten stopping distances, Radlinski says.

This graphic illustrates two key benefits of antilock braking systems. Side force, which keeps a truck from skidding or jacknifing, is greatly increased by ABS because it keeps the wheels rolling. Surprisingly, braking force also reaches its peak when the wheels are turning during hard braking. ABS, therefore, shortens stopping distances as well.

Radlinski presented a graph of what happens to both braking force and side force (what keeps a tire from skidding sideways) as a wheel locks up when the driver hits the brakes. In addition to the loss of almost all side force, locking the wheels reduces stopping force by as much as 20 percent. A rolling tire tread grabs the road much tighter than sliding tread. ABS optimizes braking wheel rolling speed at about 85 percent of cruising rolling speed, which prevents the loss of stopping power that occurs when a wheel locks. Where ABS makes the most difference is lightly loaded situations where the brake system is inappropriately large and poorly balanced. At these times, ABS may cut stopping distance in half.

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Radlinski outlined the many nasty scenarios ABS prevents. The most severe one is the panic braking situation where the tractor’s rear spins out and into the trailer – the classic braking jacknife. It’s hazardous because, unless the driver catches it right away, he can’t stop it. If he’s panicked, chances are he won’t even have the nerve to try. Other nasty situations include the trailer wheels locking first when the trailer’s empty, causing it to spin out of the lane, especially when on a crowned road.

Training roadside inspectors to at least check the ABS warning light would tell them whether or not the ABS computers had detected any faults. That’s a good – though not completely foolproof – indication of whether or not the system is working. There are a number of variables officers would have to be able to deal with in order to interpret the warning light indication. Among them are the year of both tractor and trailer and which component or components of the combination have ABS.

At this point, an ABS warning light check is not in the CVSA inspection criteria. Nor is it part of an annual inspection, though some jurisdictions have been known to put people out of service if the system doesn’t work. But CVSA has already begun putting it in its inspector’s training course. And, judging by the committee members’ positive reaction to the presentation, it may one day soon become part of the inspection criteria. “Drivers are almost always positive about ABS benefits,” Radlinski says. So, why not begin regular checks and repairs of ABS in your fleet?