Give Yourself a Brake
Decelerating properly in different driving situations will keep you safe and maximize brake longevity
Recommendations about properly braking ultimately begin with suggestions about how to drive smartly. Many situations where hard braking is necessary could have been avoided by following a few of the basics all professional drivers should practice — slow down, allow a safe distance between you and the vehicle ahead, anticipate last-second maneuvers by four-wheelers, select the proper gear on downgrades.
At tank line Trimac U.S., braking is covered both during driver orientation and defensive driving sessions. Says Neil Voorhees, director of safety and security: “Braking is more defensive driving than actually putting your foot on the pedal. We’re focusing on proper following distance, adjusting your speed for conditions, being more proactive. By the time you have to slam on the brakes, you’re in trouble.”
One of the most challenging braking situations arises when traveling downhill. Today’s technique differs sharply from past advice. “The old adage was to put 5 to 10 pounds air pressure on your trailer brake and ride the pedal down the hill,” says John Hawker, service engineer, Bendix Commercial Vehicle Systems. “The problem is you develop heat, and the brakes would never cool until you got to the bottom.”
For example, a 6-mile downhill at 6 percent grade puts a severe strain on your brakes, says Richard Martin, manager of technical training at ArvinMeritor. He says this equates to a 1,900-foot elevation drop, resulting in a terminal velocity of 238 mph. “This would be the velocity of your rig, neglecting air and rolling resistance,” he says. “Suppose you average 30 mph coming down. The run will last 12 minutes. Sixteen stops from 60 mph in 12 minutes is a lot of stopping. Obviously your brakes had better be right and you had better use the right braking technique if you want to make it safely to the bottom.”
Today’s technique is snubbing, where you apply intermittent pressure to your foot valve, which applies pressure to all your service brakes, as you descend. Each time you push on the pedal, the speed is reduced by 5 to 6 mph.
“The key is not the speed drop, which will depend on vehicle weight, grade and other factors,” Martin says. “You have to get application pressure high enough to get all your brakes working. The application pressure should be high enough to ensure all the brake chambers apply and all linings make solid contact with the drums — about 20 psi or higher. What you want is all the brakes working some of the time, not some of the brakes working all the time.”
If you top the hill in fifth gear, engage your engine brake, which will allow you to run 10 to 15 mph slower, Hawker says. “As you get close to the governor speed of the engine, step on the pedal and slow your vehicle down to 1,200 to 1,500 rpm, take your foot off the brake and let the rpm slowly rise to 1,800 to 2,000 rpm and then snub [the brakes] down again. While my foot is off the pedal, the brakes are cooling.”
Hawker says that while negotiating a steep downgrade like the Grapevine in California, you might be off your brakes for a minute or 90 seconds and on them for a minute. You maintain the gear in which you topped the hill without trying to upshift to build momentum for an approaching uphill grade, he says.
“If you follow a good truck driver down a hill, you’ll hardly see any brake lights and you’ll only be going 32 to 35 mph,” Hawker says. “When he gets to a curve, you’ll see the brake lights come on as he snubs down the brakes. Then he’ll let it go back up to speed again.”
When driving on ice, wet roads or other slippery surfaces, the proper technique is to tap your brakes or steer out of trouble, depending on the conditions.
Voorhees says his company’s training covers how to tap your brakes, though anti-lock braking systems help drivers compensate in many situations. The key thing to understand is that a driver shouldn’t rely too much on ABS and disregard safe driving practices.
In stop-and-go driving, braking is less crucial than maintaining a safe distance in traffic and scanning for potential trouble. Gearing down and maintaining a consistent speed will reduce the need to brake. Voorhees says drivers complain that auto drivers dart into open spaces in front of them. “I ask them if they’ve ever ended up going backward in traffic,” he says. “That gets a laugh out of them, but it makes the point that you’re still moving forward. I don’t think we as an industry talk enough about actual braking. We’re trying to be more proactive to get drivers in a position where they never have to slam on their brakes. That’s where the focus needs to be in the trucking industry.”
One step Trimac has adopted is achieving good results. They now monitor through the Qualcomm system when a driver has a “hard brake event.” This occurs whenever a driver decelerates at least 10 mph within a second. An alert goes to Voorhees’ email detailing where the event happened and how quickly the driver decelerated.
“Drivers are calling their managers ahead of time and telling them that ‘Neil is going to be calling you because I had a hard brake event,’” Voorhees says. “It’s really raised awareness that they shouldn’t get in one of those situations. We’ll have it installed on all of our vehicles by the end of the year.”
INSPECTING YOUR BRAKES
When you need your brakes, you want them in good working order. Too many accidents occur when brakes fail.
John Hawker of Bendix notes that drivers are allotted by federal law 15 minutes for both a pre-trip and post-trip inspection. This is time well spent, he says. “In pre-trip the driver should walk around the truck, apply the brakes, release the brakes, looking and listening for air leaks,” he says. “An air leak may create brake imbalance.
Post-trip do the same thing, and if you find something, write it up. Problem is that it isn’t done very often.”
Here are recommended inspection steps:
• Build air in the vehicle to the governor cut-out;
• Turn off the engine;
• Walk around the vehicle listening for air leaks;
• Release the parking brake while the trailer brake is applied. This will help detect a leaking diaphragm or a leaking O ring;
• Have an assistant apply the truck brakes while releasing the trailer parking brake. Do a walk-around listening for air leaks;
• Finally, measure brake push-rod travel and compare with the U.S. Department of Transportation and Commercial Vehicle Safety Alliance out-of-service criteria.
REMEMBER WHAT’S BEHIND YOU
When applying their brakes, tanker drivers should remember the force of the load behind them. In training at Trimac U.S., drivers are taught about the “slosh and surge momentum” that builds up from the tanker load, says Neil Voorhees, director of safety and security. That force is apparent when preparing to stop.
“It’s important you don’t run up on a light and stop but that you leave a proper stopping distance,” he says, “because when that surge hits, it can push you a good distance. Slow down, brake gently and leave enough distance from the vehicle in front of you so you’re not pushed into that vehicle or intersection. Leave at least two vehicle lengths, because you never know how far it’s going to push you.”
