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Euro 7 Brake Particle Emissions Testing

Euro 7 Brake Particle Limits and the Filter Weighing Requirements Behind a Reliable MG/KM Result

Home Cerca prodotti per applicazione Applicazioni di pesatura in laboratorio Euro 7 Brake Particle Emissions Testing
Euro 7 Brake Particle Emissions Testing
Euro 7 Brake Particle Emissions Testing

With Euro 7, under the framework of Regulation (EU) 2024/1257, brake particle emissions become a regulated part of vehicle type approval for the first time, requiring manufacturers to measure and report the mass of particulate matter generated during braking. This measurement is conducted using a differential weighing process: a conditioned filter is weighed before testing, exposed to brake-wear particles during a standardized brake cycle, and then weighed again. The increase in filter mass, often less than one milligram, determines the brake particle emissions value reported for regulatory compliance.

Since the mass of the collected brake particles is very small, disturbances in the weighing process can significantly affect the measurement result. Accurate results depend on three elements:

  • A (ultra)-microbalance with sufficient measurement repeatability to quantify the small filter mass gains

  • Control of environmental and electrostatic influences through proper filter conditioning, handling, and weighing procedures

  • Documented measurement traceability, including calibration records and evidence that the balance performs adequately for the expected filter mass gains.

Euro 7 Brake Emissions Limits and Phase-In Dates

Unlike previous standards that focused solely on exhaust (tailpipe) emissions, the new Euro 7 regulation also introduces limits for non-exhaust emissions including particles generated during braking.

Regulation (EU) 2024/1257 entered into force on 28 May 2024 and introduces brake limits in stages by vehicle type:

  • new M1 and N1 vehicle types from 29 November 2026;

  • all new M1 and N1 registrations from 29 November 2027;

  • heavy-duty vehicles from 2030, once their measurement method is finalized.

The initial Euro 7 brake-emissions limits are based on PM10 mass emissions. Particle number down to 10 nm (PN10) is sampled and reported under the same procedure, but it does not yet carry a limit. The regulator has identified PN10 as a placeholder for a later requirement.

The limits become stricter over the decade and distinguish battery-electric vehicles from internal combustion engine (ICE) vehicles. Regenerative braking reduces friction-brake wear, but it does not eliminate it. The light-duty limit table below highlights the regulatory requirements manufacturers must meet.

How Euro 7 Brake Particle Emissions Testing Works

Brake-particle measurement is based on UN GTR No. 24, adopted in June 2023 as the world’s first harmonized brake-emissions procedure. Its binding type-approval form, UN Regulation No. 179, was adopted at WP.29 in March 2026 and is expected to take effect in September 2026.

The test runs a complete brake corner—disc, pads, and caliper—on an inertia dynamometer inside a sealed, cooled enclosure. The enclosure is supplied with HEPA (H13) and activated-carbon-filtered air to ensure that measured particles are attributed to the brake system.

The brake test is using the WLTP-Brake cycle. It is based on real-world driving data from 5 world regions, 10 trips, and 303 brake events over about 192 km.

Downstream of the enclosure, the sampled air splits into two isokinetic lines. These lines draw the particles through PM10 and PM2.5 cyclones and then into gravimetric filter holders.

The filter weighing that follows uses the same differential weighing method applied in gravimetric particulate-matter testing for exhaust and ambient PM. In parallel, a separate line sends the sample through a volatile-particle remover before it reaches the particle counter.

The process converts corner-level measurements into the final vehicle result in three steps:

Each brake corner is tested separately

Each brake corner is tested separately

The results are weighted to reflect the contribution of each axle

The results are weighted to reflect the contribution of each axle

The weighted values are combined into a single vehicle emission (mg/km)

The weighted values are combined into a single vehicle emission (mg/km)

The counting line supports the future PN requirement. For current compliance, however, the filter line is decisive because the regulated output is mass.

Why the Weighing Step Decides the Result
Why the Weighing Step Decides the Result

Why the Weighing Step Decides the Result

Every upstream step is designed to produce one decisive value: the net mass collected on the filter. For a 47 mm PTFE membrane, a brake-dust sample is often below one milligram. At these low mass levels, it is important to verify that the balance can achieve the required measurement uncertainty. Readability alone does not determine whether a balance is suitable. A readability of 0.1 µg, for example, does not guarantee reliable results if the measured mass difference falls below the balance’s minimum weight, defined as the smallest load that can be weighed within a specified uncertainty. A reliable brake-PM result therefore needs documented proof of minimum weight and measurement uncertainty, not just a displayed mass value.

PTFE creates a second challenge: it readily accumulates electrostatic charge. That charge can influence the weighing by several micrograms. When measuring the small differences typical of brake particle emission testing, electrostatic effects can become larger sources of error than the balance’s own repeatability.

The low density of PTFE filters introduces a third challenge: air buoyancy. Because PTFE filters are less dense than conventional calibration weights, buoyancy effects influence the weighing result. The magnitude of this effect depends on air temperature, pressure, and humidity.

Both electrostatic effects and air buoyancy must be controlled as part of the weighing process rather than treated as acceptable sources of variability. In addition, filters must be properly conditioned to ensure a stable mass before weighing. Brake-emissions filters are therefore conditioned and weighed in a controlled environment, typically within a HEPA-filtered chamber maintained at approximately 22 ± 2 °C and a relative humidity of 45 ± 8 % RH. Reference filters are commonly used to verify environmental stability and detect potential measurement drift.

Accurate weighing is only part of the task. The testing workflow also involves a substantial number of filter measurements, increasing both workload and the risk of handling errors. In a typical campaign, three test cycles with four filters each generate 12 sample filters. Since each filter must be weighed before and after testing, this already results in 24 sample weighings. Additional blank and reference filter measurements can more than double that number, bringing the total to more than 70 weighings before the emissions data can be evaluated.

METTLER TOLEDO Solutions for Brake-Emission Filter Weighing
METTLER TOLEDO Solutions for Brake-Emission Filter Weighing

METTLER TOLEDO Solutions for Brake-Emissions Filter Weighing

The challenges of brake-emissions filter weighing extend beyond achieving high readability. Reliable results require control of measurement uncertainty, electrostatic effects, air buoyancy, and a demanding weighing workflow.

XPR Ultra-Microbalances combine sub-microgram readability with the performance verification and workflow controls required for reliable brake-emissions filter weighing. With readability down to 0.1 µg and repeatability as low as 0.15 µg at low loads, they support the accurate measurement of the small mass differences typical of brake-emissions testing. The micro filter weighing kit accommodates both 47 mm and 70 mm filters and uses self-centering weighing pans to ensure consistent filter positioning and minimize eccentricity effects. Internal adjustment and status monitoring help verify balance performance between service intervals.

To address the electrostatic properties of PTFE filters, METTLER TOLEDO antistatic solutions help neutralize residual charges before weighing, reducing a significant source of measurement uncertainty.

Good Weighing Practice™ (GWP®) provides a documented fitness-for-purpose assessment, demonstrating that expected filter mass gains can be measured within the required uncertainty.

LabX™ software guides users through the weighing workflow, automatically records results, applies air-buoyancy corrections, and maintains complete sample traceability together with a secure audit trail to support data integrity and compliance requirements.

For laboratories seeking higher throughput, METTLER TOLEDO microbalances can also be integrated into fully automated filter-weighing systems.

Do You Need Support?
Do You Need Support?

Specify the Weighing Setup for Your Euro 7 Brake Program

We help you select the balance, static control and automation for the filter weighing requirements of your brake emission testing. A minimum weight determination for each balance documents that the net filter loads stay within the safe weighing range.

Recommended Gravimetric Filter Weighing Workflow for Brake PM

A valid brake-PM weighing setup consists of a small number of components, and each of them controls one specific source of error. The table below lists each physical error source next to the component that limits it.

Beyond Euro 7: China 7 and Global Non-Exhaust Emissions

Euro 7 is the first major regulation to introduce limits for brake particle emissions. Similar developments are being discussed in other markets, including China, where future China 7 regulations are expected to expand the focus on non-exhaust emissions.

While the final requirements have not yet been published, the measurement principles, laboratory practices, and gravimetric weighing techniques established for Euro 7 provide a strong foundation for future brake-emissions testing programs.

Filter Weighing Guide

Filter Weighing Guide for Compliant Emissions Testing

Improve Emissions Measurement Accuracy and Support Regulatory Readiness

Test delle emissioni | Determinazione gravimetrica del particolato

Test delle emissioni - Determinazione gravimetrica del particolato

Pesata dei filtri per la determinazione gravimetrica del PM nei gas di scarico dei motori e nelle emissioni evaporative

What does Euro 7 brake particle emissions testing measure?

Euro 7 brake particle emission testing measures the particulate matter released by a vehicle’s brakes during a standard drive cycle. The process works in three steps:

  • a brake corner runs on a dynamometer inside a filtered enclosure;

  • particles are captured on PTFE filters; and

  • each filter is weighed before and after the test.

The filter’s mass gain is divided by the distance driven to produce a result in mg/km, which is then checked against the applicable Euro 7 limit.

What limits does Euro 7 set for brake emissions?

For light-duty vehicles, Euro 7 sets PM10 brake-emission limits that vary by vehicle class and powertrain. During the interim period to the end of 2034, the main limits are:

  • 7 mg/km for combustion M1 and N1 class I-II vehicles;

  • 3 mg/km for battery-electric M1 and N1 class I-II vehicles; and

  • 11 mg/km for N1 class III vehicles to the end of 2029.

From 2035, the limit drops to 3 mg/km for M1 and N1 class I-II vehicles across all powertrains. The limit for N1 class III is still to be defined. Particle number is measured under the method, but it is not yet capped.

What balance is required for brake-wear filter weighing?

Brake-wear filter weighing requires more from a balance than 0.1 µg readability. Accurate results depend on three elements:

  • A (ultra)-microbalance with sufficient measurement repeatability to quantify the small filter mass gains

  • Control of environmental and electrostatic influences through proper filter conditioning, handling, and weighing procedures

  • Documented measurement traceability, including calibration records and evidence that the balance performs adequately for the expected filter mass gains.

The XPR3U Ultra-Microbalance meets the resolution and minimum-weight requirements. For reliable results, it should be paired with Universal Antistatic Kit.

Why is static charge important in brake-filter weighing?

PTFE membranes can hold electrostatic charges. That charge can influence the balance and bias the reading by about 1 µg, even after neutralization.

At 0.1 µg readability, the error from static charge on a filter can exceed the measurement uncertainty of the balance itself. Measure the charge on each filter and remove it before you record the filter mass; without that measurement, residual charge remains an unquantified error in the result.

How many weighings are needed in one brake-test campaign?

 A brake-test campaign requires far more weighings than the number of filters. In one documented example, a single cycle of three runs with four filters each involves:

  • 12 filters in total;

  • 24 sample weighings, one tare and one loaded reading per filter;

  • 48 blank and reference weighings in the ABA scheme that brackets every sample weighing.

Together, these steps add up to 72 individual weighings for one cycle, and a campaign repeats them for every cycle. At that number, automated filter weighing removes most of the manual handling and keeps each weighing step repeatable.

Will China 7 include brake-emissions requirements?

China 7 (国七) is expected to include non-exhaust emissions from brakes and tires into type approval. The methods and limits are still under study, and no official number has been published yet.

 The regulatory direction has prompted many labs to build gravimetric weighing capacity now, before the final text is published.

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