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Author Christian Stolz discusses how the fresh regulations will heighten the expectations and prerequisites for brake pads
The recently implemented Euro 7 standards became effective on 28 May 2024. Brake emissions are now under scrutiny for the first time, impacting manufacturers and the broader automotive sector. In essence, companies selling in the EU must prioritize discovering solutions that comply with the law and diminish their ecological footprint.
Euro 7 mandates that brake abrasion be substantially restricted going forward, elevating the expectations and stipulations for brake pads. The proposal dictates that particulate emissions from brake abrasion (PM10) must not surpass 3-11 mg per kilometer per vehicle, based on the vehicle class and propulsion type. Though strides have been made in curbing vehicle emissions, specifically stemming from the combustion process, companies face growing pressure to do more.
Adjusting brake friction formulas is not as straightforward as merely replacing one raw material with another. This complexity was evident when eliminating asbestos or copper. Each material must possess the appropriate characteristics and integrity to harmonize effectively and deliver the anticipated performance. Often, multiple raw materials may be necessary to achieve the same level of performance as before.
Modifying brake friction formulas involves more than just substituting one raw material for another
Hence, limiting brake emissions is not a simple task. Contrary to common belief that most abrasion stems from the brake pad, approximately 80% of the emissions or dust on the rim results from disc abrasion. The quantity of disc material removed hinges on the chosen friction material composition of the brake pad. This factor alone is insufficient to meet the Euro 7 limits, necessitating novel and unconventional friction concepts.
Innovative approaches
All industry participants are now striving to devise approaches that conform with Euro 7 emissions guidelines. One suggested method involves capturing brake dust post-generation using filters. However, this would require OEMs to redesign their brake systems to incorporate filters. It entails adding extra components to the vehicle, which would result in increased weight and necessitate additional maintenance for cleaning, replacing, and disposing of collected brake dust emissions.
Another strategy entails directly addressing emissions and brake dust formation at the source, namely the brake pad and disc, by meticulously formulating a coordinated friction pairing. This currently seems to be the most viable path to reducing emissions, utilizing a hard material-coated grey cast iron disc alongside a custom-made friction material blend tailored specifically for the vehicle application.
To achieve the optimal application for each vehicle’s braking system, the brake manufacturer must continuously assess the impacts on performance, endurance, and cost efficiency of a friction pairing. The specialists in testing facilities and on track tests must also consistently evaluate comfort and noise levels.
The tribological and NVH (noise, vibration, harshness) performance of coated grey cast iron discs will be pivotal. Balancing low abrasion despite maximum performance and addressing emissions at their origin can only be attained by material developers and project participants working closely with vehicle manufacturers in the early stages.
Capital Investment
Alongside the technical hurdles posed by Euro 7 standards, the new regulations will also present economic challenges for some industry participants. Delivering suitable solutions for Euro 7 in the aftermarket demands substantial effort. The cost for a test bench stands at around €1.5m, with a total run time for one material lasting approximately 27 hours. This includes six cycles, each simulating 303 braking operations covering 192km. It’s evident that it will become increasingly challenging for low-cost traditional compounds to maintain a presence in the European market amidst escalating demands.
Developing a new concept necessitates significant investment and should be supported by extensive knowledge and experience. This underscores the importance for the automotive industry to collaborate with expert partners well-versed in the intricate brake system and possessing the necessary testing and development capabilities—not just in mass production.
The new standards will initially impact original equipment (OE) goods but are projected to extend to the independent aftermarket (IAM), likely through the ECE R90 directive, making Euro 7 standards pertinent for both original and aftermarket products. Moving forward, aftermarket brake pads and discs must adhere not just in terms of performance and braking action as before, but also comply with emission standards.
The reduced wear behavior will shift the replacement intervals from wear limits to time intervals
The Euro 7 homologation standards for the independent aftermarket are still evolving but are expected soon, with transitional periods likely. This transition period will provide aftermarket entities the opportunity to acquaint themselves with the various solutions advanced by vehicle manufacturers and develop and homologate appropriate products accordingly. Typically, it takes around one to two years for new vehicles to reach independent workshops, or for pad or disc replacements to be necessary. Should earlier replacements be required, due to frequent use, before the transition ends, the original parts will be available at authorized workshops to reinstate the original condition.
Ultimately, the reduced wear behavior will alter replacements from being governed by wear limits as before, to designated time intervals. Similar to a use-by date, components aged by environmental and operational factors would then necessitate replacement.
The recent endorsements from the EU Parliament and EU Council marked significant junctures in outlining the forthcoming steps and requisites for the novel Euro 7 criteria. The transitional phase allows companies additional time to pinpoint the appropriate solution that conforms with the legal obligations. However, brakes play a critical role in overall vehicle safety; hence, while curbing emissions is vital, it should not compromise braking performance.
Author Bio: Christian Stolz serves as the Vice President R&D OE at TMD Friction, a global brake maker encompassing the Textar, Mintex, Don, Pagid, Cobreq, and Bendix braking brands
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