Copper Under Pressure: What the Shift to Copper-Free Brake Pads Means for Fleets

For decades, copper has quietly done some of the hardest work in heavy-duty truck braking systems.

It stabilized friction. It pulled heat out of the pad. It reinforced the friction matrix. It helped create the all-important transfer film that makes air disc brakes perform smoothly under punishing duty cycles.

And now, it’s effectively gone.

As of Jan. 1, 2025, brake pads sold in and Washington must contain less than 0.5% copper by weight. This is a threshold widely considered “copper-free” by regulatory agencies.

While the laws originated at the state level, the industry has standardized nationally around compliant friction formulations rather than building state-specific pads.

For fleets, the transition has been largely invisible. However, some fleet managers are raising concerns that reduced-copper or copper-free air disc brake linings aren’t holding up as well in certain operations.

A few have even floated the idea of stepping back from air disc brakes altogether, especially on trailers. That’s a serious claim in a market where air disc brake (ADB) adoption in linehaul applications now exceeds 50%.

So, what’s really going on?

To understand the impact, it helps to start at the beginning and understand why copper became so central to heavy truck braking in the first place.

Why Copper Was Critical in Heavy-Duty Brake Pads

Copper has been used in brake friction materials for more than a century. According to Richard Conklin, Director of Engineering, Wheel End, Bendix Commercial Vehicle Systems, its use dates back to 1913. It became widespread by 1918, often in mesh or screen form to reinforce friction materials.

Over time, copper became a staple in both disc pad and drum lining formulations for commercial vehicles.

“Copper has been used as an additive in brake friction formulations for decades,” says Jeff Morris, director of axle, brake, and wheel-end systems at Meritor. “It was widely adopted in the 1980s as the industry evolved away from older formulations that included lead.”

Its appeal wasn’t based on a single magic property. Rather, it was an important component in a combination of friction materials.

Julia Cilleruelo Fernandez del Moral, senior product marketing specialist for Cummins Drivetrain and Braking Systems (formerly Meritor), compares brake pad formulation to baking cookies.

“Pad formulas contain four main functional groups,” she explains. “These include fibers, fillers, friction modifiers, and resins. And each contains up to 20 different elements or compounds.

"Engineers often describe it like a cookie recipe. That’s because if you swap out a single ingredient, it can change the texture, structure, or how the brake pad behaves.”

And while copper wasn’t the only ingredient in the brake pad recipe, it was most certainly an important one.

Why Air Disc Brakes Relied Heavily on Copper

It was arguably even more important for air disc brakes. Because they generally operate at higher temperatures than drums, many air disc brake pads are semi-metallic and contained more copper.

Sudhive Nair, head of chassis control North America at ZF, explains that copper served multiple roles in air disc brake pads:

• It acted as a friction modifier, helping stabilize the coefficient of friction.
• It reinforced the pad structure alongside steel fibers.
• It conducted heat efficiently away from the friction surface.
• It helped form and stabilize the transfer layer — the thin film that disc brakes rely on for consistent, predictable stopping.

In disc brakes especially, Nair explains, copper’s ability to smear and fill surface asperities helped promote an even transfer film between pad and rotor. That stability is critical during heavy braking events.

Surface asperities are the microscopic peaks and valleys on a brake pad and rotor surface — the tiny high spots where contact and heat begin during braking. Copper helps fill in those irregularities and promotes a smoother, more stable friction layer between pad and rotor.

Why Copper Is Being Phased Out

So why is copper suddenly on the outs? The issue isn’t performance. It’s environmental impact.

Copper particles from brake wear can wash into stormwater systems and eventually reach waterways. Research has shown that elevated copper levels can be toxic to aquatic life, especially salmon.

In 2010, California and Washington passed laws (often referred to as the Better Brakes Law) to limit copper and other heavy metals in brake friction materials.

From an OEM perspective, there was understandably little appetite for producing different pad formulations for different states. Instead, the industry standardized around compliant friction.

In 2015, industry groups partnered with the Environmental Protection Agency under a Memorandum of Understanding to voluntarily phase down copper content.

To comply with new regulations, pads are now clearly labeled by compliance level:

• B-Level (≤5% copper) by 2021
• N-Level (≤0.5% copper) by 2025

Enforcement focuses on manufacture and sale, not end users. That means existing parts inventory can still be used, and that fleets are not at risk of being cited for running older pads.

Some trucking fleets don't feel that the new reduced-copper formulations are living up to the same standard.

Replacing Copper: No Silver Bullet

Removing copper wasn’t as simple as swapping one ingredient for another.

“There is no single 1:1 replacement,” Nair says. “Formulations shift by increasing steel fiber reinforcement and using more complex combinations of lubricants, abrasives, and modifiers.”

Silicon, steel, iron, and proprietary metallurgy and resin compounds can serve as functional substitutes, adds Conklin at BendixCommercial Vehicle Systems.

“Brake friction remains an innovative space," he says. "Silicon, steel, iron and other proprietary metallurgy and resin compounds can act as functional substitutes for copper. Every application is different, and every route demands something different from the truck. But our expectation is similar performance between the outgoing materials and the new N-level pads.”

Regardless of the materials selected, Hendrickson emphasizes that brakes must be engineered as a system.

“In a disc brake, the pad and rotor are developed as a friction couple,” Morris explains. “Using non-OE replacement pads can affect rotor life, even if the pad itself appears to perform well.”

In some applications, Hendrickson required adjustments to brake chamber sizes to maintain torque output with N-level friction.

R&D and Lots of Testing

According to Cilleruelo Fernandez del Moral, Cummins spent four to five years developing and validating N-level formulas through laboratory testing, FMVSS validation, and fleet trials.

As a result, its current N-level friction used in Meritor EX+ LS, EX+ L, EX+ H and Quadraulic disc brakes meets or exceeds previous wear and performance expectations, she says.

Nair says ZF put more than 10 million test miles on reduced-copper pads to determine their capabilities. The company also conducted additional million-mile tests on zero-copper pads. And both pad types met all required durability standards.

From an OEM standpoint, the message is consistent: Performance parity has been achieved.

Why Are Some Fleets Concerned?

Brent Hickman, senior manager of equipment and maintenance at Pilot Company, says he’s seen the company’s total maintenance costs increase by about 21% year over year, and a big part of that is brakes. Pilot specs air disc brakes on both tractor and trailer.

The company brake wear has decreased between 28% and 35% depending on whether its the truck or trailer. The cost of brakes and brake repair have risen about 26% year over year.

Hickman says the materials that met the B-level standard starting in 2021 are now at the point where “less than desired” brake pad wear has become evident.

"We're at that point in the life cycle of the fleet that have these new pads where we're seeing a ton of failures," he says. And those failures also cause damage to rotors and calipers.

He believes part of the problem is that some of the materials used to replace copper produce a vapor or fog that creates a sticky coating on pads and rotors and degrades performance.

"I'm at the point now, I'm almost ready to go back to drum brakes on the trailers. And I know four fleets have done that. Problem is … it's not an immediate gain. I'm not going to go swap all the trailers over that are currently discs to drums. That's about 12 grand a trailer."

Tips for Copper-Free Brake Adoption by Fleets

Suppliers have some advice for fleets to help avoid problems.

Air disc brake adoption has surged over the past several years, particularly in linehaul applications. But, of course, not all duty cycles are created equal.

“Some applications are better suited for air disc brakes than others,” explains Cilleruelo Fernandez del Moral. “Duty cycle and operating environment can influence pad life.”

One potential issue is misapplication.

“If a fleet selects a linehaul N-type friction mix and uses it in a severe-service application, they may experience higher wear,” she says. “That would be the same if they used an A-type linehaul pad in a severe-service application.”

In other words, copper-free friction isn’t inherently weaker — but it still must match the job.

Maintenance practices also matter.

Disc brake pad wear inspection requires wheel removal, which some fleets defer. If pads wear beyond recommended limits, progressive rotor damage can occur. This can dramatically increase repair costs.

To address this, Cummins is working with OEMs to deploy electronic pad wear indicators and explore predictive sensing technologies.

"Of course there are offsets to performance when substituting these other materials for copper that affect overall torque output and wear performance at various temperatures," says Keith McComsey, technical sales lead (wheel-end) at Bendix Commercial Vehicle Systems. "So it is a delicate balance to try to maintain those levels of performance with these other materials."

McComsey says fleets concerned about performance issues should ask OEMs and brake manufacturers if there are differences in torque output and wear so they are educated as to the safety impacts from previous lining materials to the new materials being used today. 

"Keeping in mind, though," he adds, "that brake manufacturers and OEMs are mandated to still maintain FMVSS-121 standards for reduced stopping distances and parking capabilities." 

Hickman says Pilot is experimenting with and looking at some active brake wear indicators that measure piston travel and can provide a measure of pad thickness.

"I can see how much it uses, so maybe we can get a better idea before we end up needing calipers and rotors."

Hendrickson stresses that brake service should be performed across the axle to maintain balance.

The larger point: Disc brakes remain both system-sensitive and maintenance-sensitive. Copper-free friction hasn’t changed that.

Cost Pressures and the Fleet Equation

One issue suppliers and fleets face is that copper-free pads can cost more to manufacture.

That’s because alternative materials and reformulated compounds often require additional engineering and processing.

“Using alternative materials without compromising performance has the potential to increase cost,” Morris says. “When combined with tariffs and supply chain disruptions, there could be upward pressure on brake pad costs.”

Nair at ZF agrees that copper-free pads tend to be more expensive to produce, though what fleets see on the price tag depends on distribution and market factors.

At the same time, air disc brakes still offer advantages that fleets continue to value:

• Shorter stopping distances
• Improved fade resistance
• Easier pad replacement
• Better performance in repeated braking

Suppliers understand those concerns, Conklin adds. "“New expectations tend to drive investment and cost," he notes. "And we keep a close eye on minimizing the total installed cost for fleets.”

The question then becomes whether incremental friction reformulation cost outweighs those benefits.

So far, adoption trends suggest fleets still see value.

What Copper-Free Brake Pads Mean for Class 8 Fleets

Copper’s role in brake friction was significant. It reinforced. It lubricated. It transferred heat. It stabilized friction.

Its removal forced a fundamental reformulation effort across the industry. That work took years of engineering and millions of validation miles.

Today, all major OE brake suppliers have transitioned to N-level copper-free formulations.

From their standpoint, performance targets are being met.

From the fleet standpoint, success still hinges on three fundamentals:

1. Proper application spec (linehaul vs. severe duty)
2. Regular pad wear inspection
3. System-level service discipline

Air disc brakes are now mainstream in Class 8 linehaul. The copper phase-down arrived just as adoption crossed the 50% mark.

That timing may feel uncomfortable to some fleets experiencing unexpected wear changes. But the evidence suggests the story isn’t about copper disappearing. It’s about friction evolving.

And as with every major brake material transition — from asbestos to semi-metallic to today’s advanced composites — the industry will adapt.

Copper helped carry heavy truck braking for nearly a century. Now it’s up to a new generation of materials to carry it forward.

Editor's Note: HDT Editor and Associate Publisher Deborah Lockridge contributed to this story.