As Canadian truckers hop behind the wheel of new tractor-trailers, they can finally bask in the bulb-checking glow of ABS warning lamps, each clicking off in their silent promise that wheels won’t lock up.

Anti-lock brakes finally became the law of the land for new Canadian trucks, buses and trailers as of April 1, when our regulations caught up with those in the U.S.

Granted, anti-lock brakes (ABS) are nothing new to the world of trucking. They’ve been on the market for the last decade, with such names as Bendix Commercial Vehicle Systems, Dana/Eaton Roadranger ABS products, Haldex Brake Products, and Meritor Wabco Vehicle Control Systems stamped on the side. (Wabash National even has a proprietary line for its trailers.) But while such brakes are superior to their predecessors, many Canadian buyers were opting for traditional brake plumbing because it was simply less expensive than its electronically modulated counterpart. One brake manufacturer admits that less than a third of its Canada-bound equipment was fitted with the appropriate ABS sensors and modulators prior to the April 1 deadline.

Then again, buyers weren’t the only group slow to jump on the ABS bandwagon. Canadian regulators had opted for a wait-and-see approach when the U.S. announced its second attempt to require trucks to have anti-lock brakes. After all, the approach has worked to our advantage in the past. Such an approach saved Canada from the fiasco of requiring problematic versions of the so-called “121” brakes that were forced on U.S. truckers in the 1970s.

But the latest brakes are nothing like their predecessors. A modern ABS configuration won’t only keep your rig on the straight and narrow in the event of a panic stop, but it will help prevent flat spots on tires.

Sure, such a system is only meant to activate every 12,000 to 15,000 miles according to one U.S. study; about four to six times per winter. But it will make quite a difference when it does activate to keep your wheels rolling.

The benefits of rolling wheels are obvious. If the tractor’s drive wheels lock up, you’ll find yourself in a jackknife. If the trailer’s wheels lock up, you may be treated to a clear view of the writing on the side of the trailer, as it swings toward the West Coast mirror.

Electromagnetic sensors act as the eyes of these systems, tracking the rotation of toothed wheels mounted by wheel ends, and send information to an electronic brain known officially as an Electronic Control Unit (ECU). If a wheel locks up, the electronics tell the appropriate modulator – basically a valve – to limit the air feeding into a brake chamber, allowing the wheel to continue to rotate.

While anti-lock brakes are better than non-modulated designs, don’t expect your equipment to come to a dead halt sooner than a truck equipped with conventional brakes.

“Stopping distance is more of a function of the power of the brakes,” says Eaton’s Rick Youngblood. But if you have a completely equipped configuration – both tractor and trailer – you can take comfort when applying the brakes harder and faster. “You can apply and hold pressure on the brakes,” Youngblood says. “Typically it’s better for maintaining the vehicle steering and control.”

Granted, there are a few cases in which ABS-equipped trucks might need more distance to stop than their traditionally plumbed counterparts. When you’re skidding on a surface of ice that’s covered with snow, for example, the snow plowed in front of skidding tires can help slow you down, Youngblood admits. But the modulated pumping of brakes will allow you to maintain control at the steering wheel.

If you have a mixed system – say, with ABS on the tractor but a traditionally braked trailer – your safest approach is to control brakes in a conventional manner, modulating the brakes with the pressure of your foot, he adds.

“The regulation is the starting point only. It’s not the finish line,” says the Canadian Transportation Equipment Association’s Al Tucker, referring to the benefits of spec’ing a more extensive system than the law requires. “If they (customers) want to pinch pennies, there’s ways to do it. But brakes, that’s one place you shouldn’t shortchange yourself.”

It all comes down to counting your S (sensors) and Ms (modulators).

A greater number of sensors will do the best job at preventing tire flatspotting, watching more wheels to ensure that they don’t lock up. A greater number of modulators, meanwhile, will control more individual wheels, meaning better stability and stopping power, particularly on an uneven surface.

Legally, each new truck, tractor or full trailer now needs an anti-lock system that controls at least one front axle and one rear axle. The wheels on one tractor axle need to be controlled independently, and no more than three of a tractor’s wheels can be controlled by one modulator. That makes a 4S/3M system the minimum requirement, although most trucks are built with superior 4S/4M systems.

To be street legal, a trailer needs a 2S/1M system, with the sensor mounted on the axle that’s most likely to lock up – typically the lead axle if the trailer rides on steel springs, or on the rear axle if it has an air ride suspension. The same system may even work on a closely centred tri-axle, with an ABS relay valve feeding all six service brake chambers. It will even control the flatspotting on a tire dolly.

But while the same system is legal for eight axles, you’ll want to order a more expansive system if you want to take advantage of the benefits that a proper ABS-equipped trailer can offer.

The next question usually relates to choosing side-by-side or axle-by-axle configurations.

“In some cases, with 1M or a single valve, you get almost the same braking performance with less plumbing, less hardware than the side-by-side. And with the side-by-side, the minimum number of valves you need is two,” says Bob Koelzer, principal ABS engineer for Haldex Brake Systems. “But a side-by-side (configuration) gives you performance advantages when you’re on a split surface, say with ice on one side, and damp or wet asphalt on the other.”

With a side-by-side system, the tires on the wet or damp asphalt have a better chance to grip the road and offer a shorter stopping distance.

A side-by-side system, for example, may be needed with two sensors on a lead axle and one modulator controlling each side of the trailer if the sensor location is limited by something like a steel suspension. On a quad, the lead axle can be controlled using a side-by-side configuration, with the tandem applied and released based on sensor readings from the middle axle of the tridem, with all the axles controlled as one.

Meritor recommends a 4S/2M system for tandem semi-trailers, tri-axles or full trailers with less than 60-inch axle spacings. If the spacing is greater, look at 4S/3M. A 3S/3M system is good for a tri-axle or full-trailer tri-axle, or full-trailer with less than 60 inches of axle spacing, the company adds. If you’re pulling a Michigan configuration trailer, you’ll want to look at a 6S/3M system that’s recommended for quad axle, tri-axle or full trailer with less than 60 inches of axle spacing.

Remember that the ABS warning lights are meant to light up when you have a problem. But that doesn’t mean you shouldn’t see them glow for a few seconds before each trip. Each version should come on for a bulb check when you first turn the truck key. If such a light remains on after a bulb check or it comes on while you’re driving more than 6.0 km-h, the rig has reverted back to its traditional brakes.

Beware, however, that these might not be the only lights that your ABS systems turn on.

Since 1997, truck manufacturers have been providing full-time power to the blue wire on your seven-pin connectors (the middle pin), to ensure a constant power supply for trailer ABS. That could mean a sudden surprise when you hook a newer tractor to an older trailer. Systems such as a dome light or lift gate may suddenly go live, since that wire has traditional
ly been used to power auxiliary equipment.

It is a truism of life, however, that all things mechanical will break. The trick is to know where problems lie.

“The main one we see that will put the (warning) light on is dirty pick-ups in the sensors,” says Dale Holman of the Georgetown, Ont.-based Truck Watch services, which specializes in brake systems. “They get a little dirt in them and they aren’t tracking the tone ring properly.

“Just wipe it off with Varsol or something; a little steel wool. Everyone has their own method, but until you do something it just won’t pick up that sensor.”

So too can it be a problem if a sensor is knocked out of position when a wheel is re-installed.

“Sometimes the sensors sit in a little clip and they’re pushed in a little too far,” Holman says.

Charlie Schott, manager of national fleet accounts at Arvin Meritor, notes that ABS faults can even help identify troublesome wheel bearings, since a signal will light once the gap between the sensor and the toothed wheel grows too wide.

“If you find a sensor that’s been knocked out of adjustment, just pushing it back is only a temporary fix,” he says, referring to how the sensor can be shifted by a wheel that becomes loose due to a faulty bearing.

And as is the case with any other electronic control, the condition of connections is key.

“If the contacts are dirty, you’re getting a lot of interference,” he says. “Mostly what I’ve seen is, as long as the plugs are clean, there haven’t been a lot of problems with them.” A dialectric grease will ensure the connections remain clean.

“Make sure the contacts are clean, and don’t go probing into the wires to look for power,” he adds of the testing method that involves piercing insulation that wraps around the wire, in a bid to find power for something like a lift axle. “I’ve seen stuff two, three months old and the things are going green. They’ve probed it, the hole’s punched in it, and the corrosion wicks along the wire. Pull the plug to test it if you have a problem.”

If you ground an arc welder to the trailer frame, your ECU will also self destruct.

“My hat goes off to these guys,” Holman says of companies that have developed the latest generation of ABS. “They’ve proven a lot of people wrong, taken away a lot of fears about the wiring.” n