Impending legislation aims to reduce stopping distances

by James Menzies

CALGARY, Alta. – The federal government in the U.S. – and most likely its Canadian counterpart as well – is considering new legislation aimed at reducing heavy-vehicle fatalities by 50 per cent.

To achieve this, the legislative body is calling on brake manufacturers to find a way to decrease stopping distances by 30 per cent.

While this may seem like a tall order, so far brake manufacturers have taken the challenge in stride.

The proposed alteration to Federal Motor Vehicle Safety Standard (FMVSS) 121 is still about five years away, but brake manufacturers are already well on the way to finding a solution to significantly decreasing stopping distances.

But what does it mean for the owner/operator or fleet manager? Well, for starters, you’d better get used to the idea of running air disc brakes – on the steer axle at least.

While the government can’t mandate the use of any one product, it can write the legislation in such a way that would make it next to impossible to meet the new standards without implementing certain technology – in this case, air disc brakes.

Some industry observers feel that’s exactly what the U.S. government has in mind as it prepares to table the proposed legislation.

The trucking industry in North America, however, has been reluctant to embrace air disc brakes, despite the fact the technology is widely used throughout Europe.

One of the main deterrents of disc brakes is the increased cost. But if the legislation is passed as expected, then the trucking industry may have no choice but to bite the bullet and absorb the cost of upgrading to disc brakes.

Of course if that happens, the cost can be expected to decrease substantially, according to Prakash Jain, director of international business development with ArvinMeritor.

“If the industry concludes that it would prefer to use air disc brakes on the front axle then the volume becomes larger and the cost would come down,” says Jain.

The more widespread use of disc brakes would also drive down costs because there would be more demand to produce the brakes domestically, rather than shipping them across the Atlantic Ocean.

“These brakes are heavy and they need to be shipped across the Atlantic Ocean so there’s an enormous cost in terms of a freight premium on those brakes,” says Anton Schneider, product line director of air disc brakes with Bendix Commercial Vehicle Systems.

Bendix has already taken steps to localize the production of air disc brakes and is expected to begin producing them on this side of the pond in 2004, which would result in significant savings for end users.

For those who are adamantly opposed to using air disc brakes, it may be possible to meet the new targets by using larger drum brakes on the steer axle.

But most manufacturers agree that’s not an ideal solution, as it opens a whole new Pandora’s box of concerns.

“By putting larger cam brakes on the front axle…we’re concerned about the drivability of that,” says Ron Bailey, technical sales manager for air disc brakes with Bendix.

Larger drum brakes tend to affect the balance of the truck under braking, which can cause safety concerns.

It also results in a significant weight increase.

Besides that, Bailey says going to a larger drum brake may not even allow the new stopping distance targets to be met.

“Unfortunately the numbers we’ve seen show that larger front drum brakes will not meet the regulations,” says Bailey.

He adds that data collected by Bendix indicates going to a larger drum brake will only result in a 21 per cent improvement in stopping distance.

If reducing stopping distances by 30 per cent or more can be achieved by simply converting to air disc brakes on the steer axle, does it stand to reason that it would make more sense to equip the entire tractor with air disc brakes?

Not necessarily, according to Jim Clarke, chief engineer for foundation brakes and wheel equipment with Dana Spicer.

“If you keep the disc brakes just on the steer axle, you’ve got the best chance for compatibility between the drives and the existing trailer brakes,” says Clarke.

“If you take a new tractor and have all disc brakes on that new tractor, it’s going to be somewhat incompatible to an older trailer with drum brakes on it.”

For instance when descending a long grade the trailer’s drum brakes could fade, requiring the truck’s disc brakes to take over more of the work load.

That could cause the disc brakes to wear themselves out and “warped rotors do bad things,” says Clarke.

Therefore, a better balance is achieved by limiting disc brakes to the steer axle, he says.

However, Bailey says Bendix has found that equipping the entire tractor with air disc brakes enables a truck to stop 39 per cent better than today’s standards call for.

That’s a five per cent improvement over test results on vehicles with disc brakes on the steer axle only.

“We’re certainly hoping that people look at that and say ‘There’s enough of a differential that yes, it makes sense to put disc brakes all the way around,'” says Bailey.

Randy Petresh, vice-president of technical services for Haldex, says meeting the proposed targets for stopping distance may not be as simple as replacing the steer axles’s drum brakes with disc brakes.

“We’ll still need to address upgrades in some applications on the rear drive axles as well,” says Petresh.

He says higher friction material, more power, or different chamber sizes may be necessary on drive axles to further address compatibility issues that may arise.

Dana Spicer has also been examining other ways to help improve stopping distances, including the use of more aggressive brakes.

“It’s a question of putting more torque on the steer axle,” explains Clarke. “That’s the part of the vehicle that can take additional torque.”

Despite the challenges, it seems each of the manufacturers are optimistic about the increased use of air disc brakes in North America.

“The growth and usage of disc brakes is going to increase on its own merit,” says Haldex’s Petresh.

“It’s a better mouse trap for many reasons and it addresses many of the shortcomings of (drum) brakes.”

But how will the industry receive the transformation to disc brakes if and when the government eventually forces its hand on the matter?

Bendix says the changes should be welcomed for many reasons.

“It’s too bad we didn’t come up with a new name (for the newest generation of disc brakes),” says Bailey. “We really are talking apples and oranges.”

For instance the latest generation of disc brakes features 17-inch rotors compared to the 15-inch rotors common on older disc brakes, and most now employ twin pistons compared to the single piston models of years gone by.

Also, “You can actually take weight out of the vehicle,” says Schneider, noting up to 160 pounds can be eliminated by switching to disc brakes.

“I think the biggest concern is can they justify the acquisition cost?” asks ArvinMeritor’s Jain.

“If the industry goes to a larger drum brake you’ve already added a cost, so the cost between a larger drum brake and air disc brakes really isn’t that significant.”

In fact, Bendix says over a five-year period, fleets could realize a 20 per cent cost benefit over traditional drum brakes. Bailey adds when the true safety benefits of air disc brakes are considered, it’s really a no-brainer.

“I believe the technology is there today that we can put brakes on a heavy truck that will allow it to stop almost like a passenger car,” he says.

When the government hears testimonials such as that, it’s little wonder it’s doing everything it can to promote the use of air disc brakes.

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