Sarah Olson has been working on brake emissions for more than twenty years. She just didn’t call it that.
“When I got into friction, I started out in the rubber industry, formulating, and moved into friction in 2004,” she told the Coffee Brake Podcast. “That was right when certain companies were coming out of Chapter 11 from asbestos, and the industry had changed there. So we have a long history of materials and emissions from that as well.”
Asbestos gave way to copper reduction, which Olson points out was itself an emissions story. Now Europe has regulated the thing directly — not the chemistry, but the particulate. “Now Europe has officially regulated the amount of emissions, not necessarily the chemical composition of it, but the PM10 size coming out of it,” she said. “And it is going to be probably adopted in other regions as well.”
What changed is that the word finally caught up to the work.
Twenty years ago, dirty wheels were a cosmetic problem
Olson’s first friction job was in a factory and its test lab. “The lab was the cleanest part,” she said. “Whether you work in friction or rubber, where I started, they’re pretty dirty. You’re just kind of used to that. You’re conditioned for that — and even the customers.”
Brake dust came up, but as an appearance issue, not a health and safety one. And in her assessment, that hasn’t fully changed on this side of the Atlantic. “Even in the U.S. today it’s still not really a focus from a health and safety [standpoint],” she said. “There’s not near as much awareness here of the potential health effects that it can have as there is now in Europe.”
Who would pass today?
With Euro 7’s brake particulate limits arriving in November, the obvious question is how the current car park would fare. Olson’s answer is a mixed bag — and it splits along vehicle segment.
Smaller vehicles: a portion would pass. Heavier and performance vehicles — Class E and F, high-performance SUVs, delivery and transit vehicles — typically would not have passed at historical Euro 6-era levels.
The solutions being deployed aren’t all materials solutions, either. Because the test schedule includes a speed requirement, some manufacturers are addressing the problem at the vehicle level. “The slower you go, the less energy you put into a stop and the less dust you emit,” Olson said. “So there’s all sorts of different approaches being taken. But in the end, there are trade-offs, like with everything else.”
Lower emissions generally mean more costly components, and sometimes a sacrifice somewhere else in the attribute set — noise being the usual candidate.
The aftermarket question nobody has answered
Near-term exposure sits with the OEMs, because that’s how the regulation rolls out: new platforms this year, and in 2027, all new manufacturing has to meet Euro 7. Brake emissions are, for the first time, a requirement inside a whole-vehicle regulation.
The aftermarket gets a runway. Vehicles on the road today are grandfathered under the regulation they were homologated to, and a typical first brake job is four to five years out — often longer, with OEMs generally targeting the warranty period.
But the runway isn’t the same thing as a plan. “The aftermarket is still not sorted out,” Olson said. Open questions include how you’d qualify which families of vehicles and brakes have to be tested for an independent aftermarket material to be compliant — and, more practically, how an annual vehicle inspection would validate that the brakes on a given car meet the requirement at all, OE or aftermarket.
More revisions are coming. Olson expects a few minor updates to be voted on in Geneva in October, and anticipates that pattern continuing.
One test procedure, or four?
Asia is moving on its own track. China 7 references the WLTP dyno schedule as a recommended standard rather than a regulation with hard limits, with an additional optional schedule alongside it. CARB has its own CBDC cycle, which it ran to collect the data underpinning its work — and which is generally considered more severe than WLTP.
Everyone would prefer harmonization. Getting it is harder. “As an industry, I think everyone would prefer that we use one test schedule and one methodology and one pieces of equipment,” Olson said. “To get that done, though, all the different countries and legal bodies have to agree to that. Everyone kind of wants it to represent their own state or country.”
Underneath the procedural debate is a more fundamental split: whether the test exists to model real-world emissions in a given region, or to serve as a consistent quality-control comparison — A against B, B against C. Europe has settled on WLTP. The open question is whether that will satisfy what everyone else is trying to accomplish.
EVs help. They don’t solve it.
Euro 7 sets 7 mg/km for a standard ICE vehicle and 3 mg/km for EVs — but pairs the tighter limit with a brake factor. A full EV’s measured result is multiplied by 0.17, on the assumption that regenerative braking handles 83 percent of the work. EVs also tend toward less aggressive friction materials.
The complication is everything the dyno doesn’t see. Corrosion, in particular. “If you get corrosion on there, you are removing that, which therefore is dust — and definitely not captured on a dyno procedure,” Olson said. “Does this test really represent what’s happening in the real world? You’re never going to have that 100 percent.”
Her summary: EVs are looked at as a solution, but they’re not the end-all-be-all solution.
The EuroBrake result
At EuroBrake in June, Olson presented PureForge results on a VW Golf. Against the 7 mg/km limit, the full-vehicle figure came in at 3.3 — run with OE low-steel pads, no special pad development, and PureForge’s proprietary rotor treatment.
The reaction, she said, was strong, and it opened the door to a lot more testing across different applications. Part of that is timing: November is close, first-run solutions are new, and uncertainty is high. “Anytime you have another technology that could offer an alternative to that, that is a huge plus.”
Olson also noticed the conference itself had shifted. Where last year’s conversation centered on treatment and rotor technologies, this year it moved toward testing, quality control, and inline production quality — the practical machinery of actually building new technology at volume.
The attendee mix changed too, with the event drawing more than a thousand people and a notably different roster. “Neo was actually on the OEM panel, Chery was there, BYD,” Olson said. “The whole car park in Europe is changing, and who those manufacturers are.”
Failing safely
PureForge is, as Olson frames it, a technology and IP company — 47 patents around a rotor treatment applied in a PVD chamber at under 300°C, roughly four microns deep.
That process description carries most of the argument. Low temperature means no additional thermal stress. A chamber process means nothing mechanical touching the part, and no constraint on rotor geometry or size. The treatment molecularly changes the surface structure and chemistry, which Olson says produces a stable transfer layer — especially with low-steel and semi-metallic pads. It’s a batch process today, with mixed part numbers in a load.
The sharper differentiator is what happens when things go wrong. If a treated rotor wears through — a rock, a hung caliper, one of the extreme situations brakes seem to specialize in — you’re on a standard rotor. The car still stops.
She contrasts that with laser cladding, where corrosion under the layer or unrelieved thermo-mechanical stress can produce warping, delamination, and cracking. “If you have a whole chunk just flake off, that can cause a pretty big problem.” And there’s an organizational cost to novelty: “Nobody in automotive likes new failure modes. We all have to rank them on our FMEAs, and that’s always a big stressor.”
Noise is the other line. Cladding’s different material properties can make noise harder to solve; Olson says PureForge’s police-pursuit applications trend quieter, which she attributes to the stability of the transfer layer. “Anytime you create a stable environment for friction and braking, that inherently introduces less vibration and excitement, and will be directionally better for noise.”
Why U.S. fleets buy it without a regulation
The U.S. has no brake emissions rule, so PureForge sells on something else entirely: total cost of ownership and uptime.
The company’s traction is in police, first responders, and fleets, backed by a three-year, 100,000-mile warranty. Olson says treated rotors used with PureForge pads and properly maintained calipers essentially don’t wear — some returned rotors at 100,000 miles still show the original grind marks from before treatment. Pads last three to five times longer than on standard grey cast iron. The company is up to roughly eight million road miles.
For fleets running hard, that math is not subtle. “There are some police fleets that’ll be changing out brakes every eight or ten thousand miles,” Olson said. Eliminating that isn’t just parts and labor — it changes the repair sequence entirely. “If you can switch your brake repairs to, I don’t even have to look at it until I’m changing tires out.”
There’s a noise story in the fleet market too. At a recent PFE conference in Orlando, noisy Tahoes were a hot topic — a problem Olson says the product solves. After she gave a brake forensics and problem-solving training session, one fleet manager stood up and advocated for the product unprompted. “That feels good, when you work for a product that people are happy with and is actually a solution.”
One constraint worth noting for specifiers: PureForge recommends its own pads exclusively, and the warranty is valid only with them. The company sells rotors and pads as a kit, and is currently testing additional pad formulations globally.
Next up is commercial vehicle and Class 8. Euro 7 doesn’t reach heavy duty until 2030, and air disc brake systems and test procedures are both still under development.
What CARB just signaled
The U.S. picture may not stay quiet. In a recent CARB webinar covering emissions broadly, brake emissions included, it was verbally stated that the board is looking to implement regulations similar to Euro 7 by 2031. Olson is careful to flag the caveat: that’s not in writing. A public comment period ran through the end of July, and the BMC submitted a letter outlining its concerns with the current status.
Olson chairs the SAE Brake Linings standards committee, and in conjunction with the other standards committees has helped reopen the Brake Environmental Task Force to engage CARB on the technical side.
The mandate is deliberately narrow. “Our main mission is to provide technical expertise to CARB,” she said. “We’re not political. We’re not going to have a position on it.” The work is comparing test procedures — outlining the differences between CBDC and WLTP, and identifying possible consolidations or compromises.
The stakes there are concrete. If California insists on an entirely different dyno procedure, Euro 7 testing wouldn’t be valid for U.S. regulation, and every program would have to be repeated.
Where to find her
Olson isn’t presenting a technical paper at this year’s SAE Brake Colloquium, but she will be giving an update during the Monday 4:00 p.m. session, where the SAE standards committees each report on their work — including the new Brake Environmental Task Force. PureForge will have a booth, and she and colleagues will be there throughout the show. LinkedIn works as well for anyone wanting the test results or to get involved with the task force.
Listen to the full conversation with Sarah Olson on the Coffee Brake Podcast.
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