In short. Brake dust is mostly iron worn off the brake disc, mixed with material from the pad, and heat bakes it onto the wheel. Many European cars, German ones included, come with low-metallic or semi-metallic pads chosen for braking at high temperature, which wear the disc harder, while the US and Japanese markets mostly use softer organic (NAO) pads chosen for comfort. That, plus open spoke designs, is why the front wheels of a BMW or an Audi go grey so quickly. It is normal, not a fault. Pad makers say ceramic replacement pads leave far less dust; the price is a pad that only has to brake within 15 per cent of the original in Europe's approval test (UN Regulation 90), and an unsettled question about heat. From 29 November 2026, the Euro 7 regulation caps brake particles on new car types in the EU and Northern Ireland at 7 mg/km (3 mg/km for pure electric cars).
What brake dust is made of
When you brake, the pad is pressed against a spinning disc and both wear. Some particles drop onto the road, some stay in the air, and some stick to the wheel.
Most of what you see on the wheel comes from the disc rather than the pad. A 2026 laboratory study of airborne brake wear found that iron, mostly as iron oxide, was the most abundant element, at 33 to 50 per cent of the mass, and traced it mainly to the disc (Hyman et al., 2026). A 2025 review puts iron at 30 to 60 per cent of the metal in brake wear (Eco-Environment & Health, 2025). The rest is pad material: binders (resins), fibres, fillers, lubricants such as graphite, and abrasives. The European Commission's Joint Research Centre (JRC) lists aluminium oxide, iron oxides, quartz and zircon as the usual abrasives (Grigoratos and Martini, 2015).
The particles are fine. The JRC review reports that about half of brake wear debris is smaller than 20 µm and almost 40 per cent is emitted as PM10, particles under 10 µm that stay in the air: brake dust is air pollution, not just dirt.
General Motors, in a service bulletin covering its cars worldwide from 2014 to 2025, gives two reasons when owners complain of heavy dust: a high-performance pad material whose by-product is black dust, and wheels with large openings between the spokes that show it off. It calls this "a normal characteristic" (GM bulletin 18-NA-067, May 2024). Our reading: the same two causes fit many German cars.
Why German and other European cars make more of it
The pad types differ by region
There is no standard definition of a pad type: makers keep their recipes private, and the names describe what dominates the mix. The families are not spread evenly across the world. A 2025 review led by JRC researchers says it plainly: non-asbestos organic (NAO) pads are commonly used in the US and Japanese markets "for comfort reasons", whereas "due to performance requirements, low-steel pads are common in Europe", together with semi-metallic ones (Christou et al., 2025).
| Pad family | What the sources say it contains | Strengths | Weaknesses | Where it is common |
|---|---|---|---|---|
| Low-metallic ("low-steel") | Organic compounds with 10 to 30 % metal by mass (JRC) | High friction, good braking at high temperature (JRC) | Harder on the disc than ceramic pads (Akebono's claim: "longer rotor life" with its ceramic pads) | Europe (Christou et al.) |
| Semi-metallic | Up to 65 % metal by mass (JRC) | Durable, conducts heat well (JRC); better at high temperature (Christou et al.) | Wears discs faster, noisier (JRC) | Europe, alongside low-metallic (Christou et al.) |
| NAO (organic) | Organic fibres, fillers and resin, without asbestos (by name) | Soft, quiet (JRC) | Loses braking capacity at high temperature (JRC) | US and Japan (Christou et al.) |
| Ceramic | Ceramic compounds and fibres; no agreed definition | Quiet, ultra-low dust, longer disc life, high fade resistance (Akebono's claims) | No standard says what "ceramic" means, so behaviour varies by recipe | Sold as an aftermarket "upgrade" for European cars (Akebono) |
Our table (16 October 2026), from Grigoratos and Martini, Christou et al. and Akebono; the "pad makers" entries are claims, not independent measurements.
One point does not fit neatly. The JRC review says NAO pads "create more dust than the other types". Pad makers selling ceramic pads say the opposite about the dust you see. Both can be true: an organic pad can lose more of its own mass, while a low-metallic pad scours more iron from the disc, and dark iron oxide clings to the wheel. We found no study that weighs the dust left on the wheel, so this is an explanation, not a measured fact.
Why European makers choose the dusty pad
No car maker's document we read explains the choice. The reviews tie it to "performance requirements": stable friction when the brakes are hot and the speed is high. Europe's approval test for replacement pads shows what is expected. UN Regulation 90 runs a speed-sensitivity test on the front axle from 65 and 100 km/h, and additionally from 135 km/h when the car's top speed exceeds 150 km/h. The decelerations from the higher speeds must stay within 15 per cent of the one from the lowest speed (UN R90, unofficial consolidated copy, Annex 3, 2.1.2). Low-metallic pads are the family the JRC describes as strong at high temperature. The usual explanation, high-speed braking on unrestricted German motorways, is plausible, but we did not find it written by a car maker.
Two other things add to what you see:
- The front wheels do most of the braking. The ADAC, Germany's motoring club, notes that the fine black dust settles first on the front wheels and can be baked into the surface by braking heat (ADAC, 1 September 2025).
- Open wheel designs. Thin spokes and large windows leave the inner barrel and the spokes in the dust stream, as GM's bulletin notes.
What a low-dust pad trades away
The clean-wheel pad for a European car is sold mainly as an aftermarket option. Akebono offers its EURO ceramic line as "the ultimate upgrade for semi-metallic and low-metallic brake pads", with "specific formulations for European vehicles", and claims it will "virtually eliminate brake dust" (Akebono EURO; Akebono, European vehicles). Brembo lists an Xtra Ceramic pad for "top end vehicles" with "clean rims" among its features and ECE R90 approval, and a Greenance pad for "dust reduction, clean rims", to be used "only with Greenance brake discs" (Brembo, range comparison). Porsche's own coated disc, PSCB, a cast-iron disc with a ceramic coating, is described as giving "significantly reduced formation of brake dust" (Porsche, original brakes).
| Option (source) | What it changes | Condition stated by the maker |
|---|---|---|
| Ceramic replacement pad (Akebono EURO) | Pad material only | Fitted to the listed application |
| Ceramic pad with R90 approval (Brembo Xtra Ceramic) | Pad material only | R90 approval for the listed vehicle |
| Pad and disc system (Brembo Greenance) | Pad and disc | "Only with Greenance brake discs" |
| Coated disc (Porsche PSCB) | Disc surface | Porsche part for Porsche models |
| Carbon-ceramic disc (Porsche PCCB) | Disc material, 50 % lighter than grey cast iron | Car maker's option, with its own pads |
Our reading of the makers' pages, 16 October 2026. The dust reductions are their claims; none publishes a same-car test against the original pad.
What you give up depends on the pad, but the direction is consistent across sources:
- Feel and bite. In Great Britain, the Road Vehicles (Brake Linings Safety) Regulations 1999 forbid supplying or fitting replacement linings for the cars they cover unless they carry an R90 approval or the equivalent EU one (regulation 4); across Europe, R90 is the reference printed on the box. R90 requires "performance characteristics similar to that of the original part": in the cold performance test, decelerations at the same pedal force must fall "within 15 per cent" of the original's (Annex 3, 2.1.1.3). A pad with R90 approval can therefore bite noticeably less, or more, than the original.
- Heat margin. The JRC review says organic (NAO) pads "lose braking capacity at high temperature". Akebono claims "high fade resistance" for its ceramic pads; we found no independent test that settles the point for ceramic pads. If you drive hard in the mountains, tow, or go on track days, the original type exists for a reason.
- Matching parts. Some low-dust systems are sold only with their own discs, as Brembo states for Greenance.
Onyx Forged does not recommend a size or an offset, and we do not recommend a brake pad either. The car maker's parts list and the R90 approval on the box tell you which cars and axles a pad is meant for. If you change pads yourself, the car must be raised and resting on axle stands, never on the jack alone, and wheel nuts go back to the car maker's torque. If the pedal feels long or soft, or the car pulls under braking after the job, have the brakes checked before driving on. Our guide to when to replace brake pads covers thickness and wear sensors.
Brake dust is now a regulated emission
European Union and Northern Ireland: Euro 7
The Euro 7 regulation, Regulation (EU) 2024/1257, regulates brake and tyre emissions "for the first time worldwide", says the European Commission (European Commission). It defines "brake particle emissions" as "the particles emitted from the brake system of a vehicle" (Article 3, point 30). Recital 20 explains why: as exhaust particles fall with electrification, non-exhaust emissions from tyres and brakes are expected to make up "up to 90 % of all particles emitted by road transport" by 2050. We read the adopted text published by the Council (PE-CONS 109/23); EUR-Lex refused our request.
| Vehicle (Euro 7, Annex I) | PM10 limit, first stage, until 31 December 2029 (Table 4) | From 1 January 2035 (Table 8) |
|---|---|---|
| Cars (M1) and light vans (N1), pure electric | 3 mg/km | 3 mg/km |
| Cars and light vans, all other powertrains (petrol, diesel, hybrids, fuel cell) | 7 mg/km | 3 mg/km |
| Heavier vans (N1 class III), pure electric | 5 mg/km | 3 mg/km |
| Heavier vans (N1 class III), other powertrains | 11 mg/km | 3 mg/km |
Testing follows the UN's global method for brake emissions (Annex III, Table 4). A second stage applies from 1 January 2030, but its values are left blank in the adopted text (Tables 5 to 7): the Commission must first report, by 31 December 2027, on measuring methods and on the level of those limits (Article 18(5)), so the figures between 2030 and 2035 are not yet known. The Department for Transport gives the dates: the requirements apply from 29 November 2026 to new light vehicle types and from 29 November 2027 to all new light vehicle registrations. It also says that a Commission act adopted on 9 June 2026, not yet in the EU's Official Journal when the memorandum was written, replaces the test reference with the new UN Regulation 179 on laboratory measurement of brake emissions (DfT memorandum, 2 September 2026).
For an owner, two limits matter: it applies to new vehicles and components that receive their approval under it, not to the car you drive now, and we did not find how it will treat a replacement pad fitted years later.
Great Britain
Euro 7 applies in Northern Ireland under the Windsor Framework, but not yet in Great Britain. The same DfT memorandum says the Government "has consulted on proposals to implement the Euro 7 vehicle emission standard in Great Britain" and will consider the brake test amendments as part of "potential future implementation plans". Replacement pads sold in Great Britain still fall under the 1999 brake linings rules described above (R90 or the equivalent EU approval).
United States and Canada
We found no federal limit on brake particles in the US; the rules target what pads contain. Washington State's Better Brakes Law limits copper to under 5 per cent by weight from 2021 and under 0.5 per cent from 1 January 2025. The state says brake pads account for up to half of the copper entering its waterways (Washington Ecology). California has similar rules, and a voluntary agreement signed on 21 January 2015 by the EPA, the states and industry groups extends the same copper targets nationwide (US EPA). Pads that meet the 2025 level carry the LeafMark with three dark leaves, a symbol adopted by the brake industry. In Canada we found no brake particle limit and no copper rule in the documents we read.
Australia
We found no Australian limit on brake particles in the documents we read. If you change more than like-for-like pads, check your state's rules on modified vehicles before driving.
What the limit means in grams: our calculation
Over 10,000 miles (16,093 km), 7 mg/km is 16,093 × 7 = 112,651 mg, about 113 g of PM10. At 3 mg/km it is about 48 g.
The limit counts only the airborne PM10. If, as the JRC review reports, almost 40 per cent of brake wear debris is emitted as PM10, a car exactly at 7 mg/km would shed roughly 7 / 0.4 = 17.5 mg of wear material per kilometre, or about 280 g per 10,000 miles. Part of that ends up on the wheels. This is an order of magnitude built on an average from the literature, not a measurement of any car.
What brake dust does to a wheel finish
The Japan Light Alloy Wheel Association (JAWA) writes that pad dust and iron powder from the discs harden together with oil if left, become very hard to remove, and can corrode the wheel's surface through oxidation and chemical reaction; its only remedy is frequent cleaning (NAPAC, JAWA division, in Japanese). The ADAC adds the heat: on the front wheels braking heat can burn the dust permanently into the surface.
How much harm it does depends on the finish:
- Painted and powder-coated wheels have a clear coat over the colour. Embedded iron can stain it, and strong cleaners can do more harm than the dust: GM rules out acid cleaners on aluminium wheels, and the ADAC both acid and alkaline ones.
- Diamond-cut (machined) faces carry only a thin lacquer over bare aluminium. If the lacquer is chipped or scoured, moisture and contaminants get under it and corrosion spreads; our guide to diamond-cut wheels explains why.
- Matt and satin finishes hold dust in their texture and cannot be polished back. See our guide to wheel finishes and their care.
A ceramic coating does not stop the dust arriving. It makes the surface easier to rinse, so less scrubbing is needed; our guide to ceramic coatings for wheels sets out what it protects and how long it lasts.
What actually helps, in order
- Clean often, with a mild product, on a cold wheel. JAWA and the ADAC agree that frequent cleaning is the remedy. Wait until the wheel is cold: JAWA warns that a cleaner sprayed on a hot wheel can make the dirt stick harder. Use a pH-neutral cleaner, never acid.
- Protect the surface. JAWA suggests a solid wax without abrasive after cleaning; a ceramic coating serves the same purpose for longer.
- Change the pads, if you accept the trade-off. A pad listed for your car and axle, with R90 approval in Europe and the UK, is the minimum. Expect a different feel and less dust, not none.
- Look at the discs too. Makers say a coated disc (PSCB) or a matched pad-and-disc system reduces dust at the source. Carbon-ceramic brakes are a separate, much larger decision.
- Brake less with the friction brakes. An electric or hybrid car that recovers energy when slowing uses its pads less. A 2022 review puts the reduction from regenerative braking at about 60 to 90 per cent, depending on the driving cycle (Fussell et al., 2022). In any car, anticipating traffic means fewer hard stops.
New wheels do not change the dust, only how much you see. Wheels with fewer, wider spokes hide more of the barrel and the caliper. Larger brakes need room inside the wheel: see brake caliper clearance. Lighter wheels reduce unsprung mass, explained in our guide to lightweight wheels and unsprung weight.
Frequently asked questions
Is heavy brake dust a sign that something is wrong?
On most European cars, no: it comes from the original pad type, and GM calls heavy dust "a normal characteristic". If the dust appears on one wheel only, or comes with a burning smell, grinding or a pull to one side, a caliper may be sticking or the pads may be worn: have the brakes checked before driving on. Our guide to squeaking and grinding brakes explains the noises.
Why do BMW, Audi and Mercedes wheels get dirtier than those of most American or Japanese cars?
Mainly the pad type: low-steel and semi-metallic pads in Europe, NAO pads in the US and Japan (Christou et al., 2025). The European pads are harder on the disc, and disc iron makes up much of the dust.
Do ceramic pads stop brake dust completely?
No. They change the pad material and, the makers say, leave much less visible dust, but the disc still wears. Even the makers' own claims stop at "virtually" or "ultra-low".
Are low-dust pads less safe?
Not if they are listed for your car and carry R90 approval. R90 requires similar performance to the original, within a 15 per cent window, so they can feel different. How they hold up under repeated hard braking is not settled by any independent test we found; for towing, mountain driving or track use, follow the car maker's specification.
Will Euro 7 make my current car's brakes cleaner?
No. The limits apply to new vehicle types from 29 November 2026 and to all new light vehicles from 29 November 2027, in the EU and Northern Ireland. Great Britain has consulted but not yet adopted Euro 7.
Does brake dust damage alloy wheels?
It can. JAWA warns that, left on the wheel, it hardens with oil and can corrode the surface, and heat bakes it in on the front wheels. Regular, gentle cleaning is the remedy; avoid acid or alkaline cleaners.
Do electric cars make less brake dust?
Usually, because regenerative braking does much of the slowing; one review estimates 60 to 90 per cent lower brake wear emissions. Euro 7 sets them a lower limit of 3 mg/km. But their brakes are used less, and a 2025 review by JRC researchers (Christou et al.) notes that corrosion from infrequent braking may add particles, so the discs still need checking: see our guide to warped or rusty brake rotors.
Wheels from Onyx Forged
Onyx Forged is a French brand of made-to-order forged wheels, designed to JWL/VIA standards. The design and finish of each set are worked out with you, including how open the spokes are and how they sit in front of your brakes: see the catalogue.
Sources
- Law and standards: European Commission, emissions in the automotive sector; Euro 7, text adopted by the European Parliament and the Council (PE-CONS 109/23), published as Regulation (EU) 2024/1257; Department for Transport, explanatory memorandum of 2 September 2026; UN Regulation No. 90, unofficial consolidated copy (2017); The Road Vehicles (Brake Linings Safety) Regulations 1999, regulation 4; Washington State Department of Ecology, Better Brakes Law; US EPA, Copper-Free Brake Initiative.
- Research: Grigoratos and Martini (JRC), Brake wear particle emissions: a review, 2015; Christou et al., Review of health effects of automotive brake and tyre wear particles, 2025; Hyman et al., Airborne brake wear particles, 2026; Beyond the tailpipe, Eco-Environment & Health, 2025; Fussell et al., Road traffic-derived non-exhaust particles, 2022.
- Makers: General Motors, Service Bulletin 18-NA-067 (May 2024); Akebono EURO and Akebono, European vehicles; Brembo Parts, pad range comparison and Brembo, Greenance; Porsche, original brakes.
- Wheel care: ADAC, cleaning alloy wheels (1 September 2025) (in German); NAPAC, JAWA division, wheel care (in Japanese).
All pages were read on 16 October 2026.
The Onyx Forged design office.