The truck stops here

Sometimes progress is worth the wait. Such is the case with truck brakes. In the works for nearly a decade, new and many would argue long overdue stopping-distance rules for commercial vehicles were finally issued in July by the National Highway Traffic Safety Administration (NHTSA). Although executives at truck brake manufacturers and truck OEMs alike have indicated they have had product ready to

Sometimes progress is worth the wait. Such is the case with truck brakes. In the works for nearly a decade, new and — many would argue long overdue — stopping-distance rules for commercial vehicles were finally issued in July by the National Highway Traffic Safety Administration (NHTSA).

Although executives at truck brake manufacturers and truck OEMs alike have indicated they have had product ready to comply with this rule for years now, the regs, which will apply to new trucks only, will nonetheless not be fully phased in for three more years. Safety-conscious fleets, however, can spec braking systems compliant with the new standards now if they so choose.

When all is said and done, the new rules will require a typical highway tractor coupled to a trailer and traveling at 60 mph to come to a complete stop in 250 ft. vs. the current requirement of 355 ft. — for a reduction in the truck's stopping distance of roughly 30%.

For heavy, severe-service tractors with GVWs above 70,000 lbs., the stopping distance requirement will be reduced to 310 ft. at the same speed. The final rule also will require that all heavy truck tractors must stop within 235 ft. when loaded to what is termed their “lightly loaded vehicle weight” (LLVW).

NHTSA's two-stage phase-in puts the highest priority on the most widely used truck-tractor units on American roads: A rig with a three-axle “tandem” tractor. These combinations, with a gross vehicle weight rating (GVWR) of 59,600 lbs. or less, must meet the reduced stopping distance requirement of 250 ft. by Aug. 1, 2011.

Two-axle (4×2) tractors and tractors with a GVWR above 59,600 lbs. (6×4) must meet the 250-ft. rule by Aug. 1, 2013. Also that year, heavy, severe-service tractors, with GVWs above 70,000 lbs., will have to meet the shorter stopping distance of 310 ft. (at the same 60-mph speed).


According to NHTSA, voluntary early compliance is permitted before the effective dates and there are reports that safety-conscious fleets are already spec'ing such braking systems. Also bear in mind that the new regs will apply only to tractors — not single-unit trucks, trailers or buses.

“This is a very tough rule, but we believe the technology is out there to help trucks comply with it,” states Eric Bolton, a NHTSA spokesman. “We're a scientific agency, so a significant amount of research went into developing this rule. We've made sure from a technology perspective that we've dotted all the i's and crossed all the t's.”

NHTSA estimates the new braking requirement will save 227 lives and prevent 300 serious injuries annually and cut property damage costs by over $169 million on a yearly basis. That savings alone, according to the agency, is expected to exceed the total cost of the rule. NHTSA estimates the incremental cost of compliance for drum brakes on a typical three-axle tractor will be $211 and the incremental cost to place air disc brakes all around will be $1,475.

Discussions that Fleet Owner editors have had with both brake supplier and truck OEM engineers going back to at least 2005 repeatedly indicated that, once it was promulgated, the new rule would be handily met and that it would indeed be a boon to highway safety.

In terms of the technology, the expectation has long been that fleets would be able to spec tractors either with what's generically referred to as “enhanced” or “wide” drum brakes or with the latest-generation air disc brakes (ADBs) — or with the combination of discs up front, drums at the rear. What's more, both drum and disc brakes were expected to benefit from new friction materials that were being developed at the same time to both improve braking performance and deliver longer life.


All of the above remains entirely the case when it comes to the initial 2011 phase-in, which again will cover most highway tractors. However, there is some expectation that the secondary phase-in of the rule in 2013 may lead to wider use of ADBs as more severe-duty vehicles will be impacted.

Truck builders indicate they expect currently available enhanced drum brakes to lend more than enough stopping power to comply with the initial, major phase-in of the new rule. “For the most part, drum brakes will handle the change, with associated systems being validated to determine if any additional changes will be needed,” says Frank Bio, Volvo's product manager — trucks. “This includes suspensions, axles and brake components including linings. [The new rule] will not eliminate the need for disc brakes in certain configurations, but for the first phase, we expect [drum] brakes to handle the requirements.”

Once the rule covers all other rigs in 2013, it appears the role of ADBs may increase. “For the 2011 stopping-distance regulation, ADBs are not required,” advises Jerry Warmkessel, Mack's marketing product manager — highway products. “Front ADBs, however, will be required” to meet the 2013 part of the rule. Therefore, many astute customers are considering spec'ing front ADBs now so as to have several generations of [those] brake parts on their shelves.”

“We're confident the new stopping distances can be met with minor modifications to our current drum and air brake systems,” reports Rich Shearing, director-product planning for Daimler Trucks North America. “But disc brakes can provide better stopping performance, and we will have a disc brake offering in the future, in particular for short wheelbase vehicles.”

Nonetheless, because they weigh more and cost more to produce (due to limited volumes) ADBs will likely remain the less popular choice for most rigs. The main benefits of ADBs are that they do not fade after repeated applications and last much longer than drums.


But those benefits are diluted by the North American operating environment, points out Ramin Younessi, Navistar group vp for product development & strategy. “Disc brakes are the standard in Europe because the trucks there stop so much more frequently over their life cycle,” he relates. “Yet as drum brakes necessarily get larger — and thus more expensive — to comply with NHTSA's new stopping regulations, the lower cost and weight advantage they enjoy may be diminished.”

Younessi adds that ADBs “married to aluminum hubs could end up weighing a lot less compared to the larger drum brakes we'll need to use with the cost difference being much less than it is today. That's when the longer life of disc brakes would become a greater factor; that's when we might start seeing some shifting [in the market].”

Still, brake engineers emphasize that the majority of tractors — tandems account for 60-70% of the highway rig population — will be stopped within the new limits by using nothing more exotic than wider “enhanced S-cam drum brakes.” Put another way, while the typical tractor fleet might opt for ADBs for their longer life and better fade performance, they won't have to because of NHTSA's rulemaking.

Aaron Schwass, director of foundation brakes for Bendix Spicer Foundation Brake LLC, points out that truck OEMs are “working with an additional 10% stopping requirement on top of the mandated 250 ft. for this first phase [of the new rule]. This is not required by law, but rather a choice regarding safety margin [built in] that many of the OEMs are taking.”


Even with that safety cushion in mind, Schwass says the braking rule for “most configurations will be met with wider steer axle brakes. And putting air discs on the steers or all the way around would work as well. But, yes, we do see the primary solution being to place wider — 16.5×5-in. — drums on the steers. Some fleets are already running these.

“For the most part, the stop can be made with more torque on the steer,” he continues, “but with some vehicles, the choice may be to place a wider drum on the drives as well. This would be done to try and improve the [brake] work balance from tractor to trailer on some vehicle configurations.”


But when the second phase kicks in and the various, less common rig configurations with different braking dynamics are impacted, then Schwass says to expect “more need for an air-disc solution” to meet the rule.

“With Phase II, the vehicles are a little harder to stop, whether a short wheelbase 4×2 or a heavier severe-service unit,” he explains. “It all will have to do with the specific dynamics when the brakes are applied. The solution in each case could be either drums or discs or a mixture — which would mean discs on the steer and drums on the drive.”

Schwass contends it's still early to state what will ultimately be engineered for vehicles that will fall under the 2013 provision. “Expect to hear more on how 2013 will be handled from manufacturers in the 2011-2012 time frame,” he notes.

According to Tom Rogers, engineering manager-brake systems for ArvinMeritor, the company has been “working on a reduced stopping distance program for over three years in anticipation of the new regulations. As a result, our S-cam drum will meet the new requirements with an additional 10% [safety] margin” and [Meritor Wabco] air disc brakes can also be used to meet the new rules.

“The 2011 reg is aimed at the lion's share of the tractor market,” he affirms. “To meet the rule, more brake torque will be required and most of that will come from using higher-performing, larger 16.5×5 drum brakes as well as higher-performance friction materials. We believe this ArvinMeritor drum package will be appropriate for all the Phase I vehicles.”

He points out that sister firm MeritorWabco “also offers air disc brakes that will meet the rule. But they will cost approximately $1,200 to $1,300 more per vehicle. We can provide these, but it is unlikely fleets will move to ADBs [given the current price premium] to meet the 2011 stopping-distance rule alone.”


Rogers also reports that most truck OEMs are seeking a “10% compliance margin” from brake systems beyond the new NHTSA stopping marks for 2011 and 2013.

“I'm hesitant to speculate too heavily on 2013 [solutions] at this point,” he continues, “but certainly some vehicles — most 4×2s — will likely not require ADBs, but those tractors above the 2011 weight limit will need ADBs or at least a hybrid setup with discs on the steers.”

Turning back to 2011, Rogers observes that “the time brake suppliers had to look at the rule made it possible to come up with a ‘drum-only solution’ for Phase I vehicles. Basically, we doubled the capacity of a steer axle drum brake” in plenty of time for the rule.

“We also have to keep in mind the fleet comfort level with drums,” he continues. “Everything from parts inventories to mechanics' experience is related to running drum brakes. Nine out of ten shops, that's what they know. That's why we never had any intention to turn away from the drum.”

Randy Petrush, vp of technical services for Haldex Commercial Vehicle Systems, says all OEMs will need higher-output steer axle brakes to meet the new rule and so the “current 15×4-in. cam brake will die like a dinosaur. What fleets will get instead is either a 16.5×5 drum or an air disc brake.”

But he says it all gets a bit more complicated once the vehicle engineering kicks in. “Each OEM, depending on the wheelbase, whether there is a setback axle and other variables, will have to re-balance the tractor [braking system] to account for the higher-capacity steer brake put in place. The braking system for each tractor model will be fine-tuned by adjusting three variables: friction material, chamber size and brake adjuster size.”

He explains that this balancing act is done so that “brakes perform with no premature locking up or pulling from side to side. This will all be transparent to the fleet owner, but the driver will feel the greater braking force being delivered to the steer axle. A 30% improvement in stopping distance after all is a fairly significant change.”

Petrush also sees the jury as still out on whether ADBs will be needed or how widely they will be deployed in 2013. “There is a greater possibility for discs on the second go-round,” he allows, “especially on the unusual applications. But if that is the case, the OEM would make the choice up front and the vehicle would come with them standard.”

Ken Kelly, vp of aftermarket business for Webb Wheel Products, points out that the rulemaking was, by his count, nine years in the making. He says the good news in all that is “now that fleets are looking closer at what will be their options, they will see a variety of solutions to pick from.”


When it comes to maintenance, he concurs that most fleets will “want to keep the simplicity of the S-cam brake. The [enhanced] drums are larger but servicing is the same and they use the same working components. Essentially, there will be little change at all in the technicians' world.”

As Kelly sees it, the near decade NHTSA devoted to writing this rule was time well spent. “The government has done a very thorough job, both of understanding the underlying issue and justifying how the reduced stopping distances will enhance safety.

“The rule,” he adds, “does not tell [the OEMs] how to meet it; that's been left up to the industry. And most importantly, it will absolutely save lives.

Inside the numbers

Implementation Date Vehicle Configuration Tractor GVWR (lbs.) 60 mph Unloaded 60 mph Loaded 60mph Unloaded 60 mph Loaded
Stopping Distance (Current) Stopping Distance (Current) Stopping Distance (New) Stopping Distance (New)
Aug. 1, 2011 Three axles 0 to 59,600 335 ft. 355 ft. 235 ft. 250 ft.
Aug.1, 2013 Three axles 59,600 to 70,000 250 ft.
Three axles Above 70,000 310 ft.
Two axles All 250 ft.
Four or more axles 0 to 85,000 250 ft.
Four or mor axles 85,000 and above 310 ft.

*Federal Motor Vehicle Safety Standards; Air Brake Systems; Final Rule, 74 Federal Register 37122 (July 27, 2009) (amending 49 CFR 571.121)

Discs: On a roll yet?

Disc brakes will undoubtedly accrue some market share in North America thanks to the upcoming revisions to NHTSA's stopping-distance rule, but also due to several other unrelated factors.

Indeed, a market research report issued recently by Frost & Sullivan projects that one of the product categories that will experience the most growth through 2015 as “leading North American heavy-truck technologies” is disc brakes.

While Frost & Sullivan pegged the “installation percentage” for disc brakes in 2005 at just 4.3% on Class 7 and 8 trucks, it forecasts that penetration will mount to 10% by 2015, according to Sandeep Kar, manager of commercial vehicle research.

That would surely represent a nice gain for a safety technology that despite oft-stated performance advantages has long been viewed by American fleet owners as a “pricey” and at least somewhat exotic alternative to familiar S-cam drum brakes. Kar says disc brakes will be spec'd more over the next decade in part due to the requirements of some vehicles to meet the 2013 phase of the new NHTSA stopping-distance rule.

But he says discs will also gain market share as more fleets become aware of their performance factors, including improved power regeneration for hybrid-drive trucks, and because of the general trend toward “harmonization of global truck platforms” among North American and European truck OEMs especially.

It may yet be many years before the disc becomes the de facto standard brake on heavy trucks in the U.S. and Canada, but it's safe to say it has begun to get on a roll.

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