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Brake Cooling and Automotive Design

By: Dr. Mo Esgandari

The very fundamental functionality of conventional brake systems is based on friction, which inherently generates heat. If not managed, the high temperatures in a braking scenario can cause permanent damage to the brake disc and friction material surface in the brake pad, which itself can cause lack or loss of functionality (brake fading). So how do brakes cool down? It’s quite simple: air-flow.

On the other hand, in the modern era of automotive design, aerodynamics and drag play a major role in the car design and sometimes even overshadows the aesthetic element. Most modern cars have less ground clearance compared to their previous generations. A lot of the modern cars have a larger bumper surface that covers a greater area of front of the car. The apertures on the bumper where air can flow in the right volume and actually reach the brake systems to cool them down have become very limited, and even those apertures are not open all the time to help with the aerodynamics.

This is where accurate modeling and analysis of the airflow comes into play, to balance these conflicting attributes and deliver the best compromise. This is the game where fraction of a millimetre becomes a great deal; so, does the accuracy of the simulation and the correlation to the reality.

This is an example where speciality in brake systems alone might come short in delivering a system for the vehicle and this is where you can seek help from the industry experts whose experience is beyond one specific area and can enable you and your organisation deliver a system in a complex product.

Dr. Mo Esgandari has over a decade of experience in Brake NVH research & development and has published in various academic journals. Mo also has a comprehensive hands-on automotive design and engineering experience delivering various vehicle programmes. Mo is one of the instructors on Brake Academy.
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John DeConti
John DeConti
Feb 07, 2022

Yes, the trade offs between engineering disciplines is complicated. Increasing aerodynamic losses to increase brake cooling, and taking it anther step to add weight to make those cooling paths active.

Having attending many SAE Brake Colloquiums over 30 plus years, I have seen presentations where actual test results in vehicles and then simulation on a brake dynamometer, show that air cooling in many applications is non-existent. All of the kinetic energy is transferred into the thermal mass of the brakes. Even with high performance cars, the fact that brakes get to glowing red hot is evidence of the simple fact that brakes can absorb energy much faster than they can dissipate it.

Wouldn't it be great if there was a…

Replying to

John that's a great observation. The performance of the brake cooling systems (active vanes / ducts / scoops / etc) heavily relies on the simulation work conducted in the design and engineering phase and if they're not simulated accurately they might not deliver the right air-flow / cooling. CAE model build and analysis is among the topics we discuss in our courses. Curious about the liquid-cooled design. What liquid is used for this to have a high boiling temperature and a high thermal capacity ? How is the thermal expansion managed ? And how would this compare with the conventional brake systems in terms of tooling / material cost per unit ? Thanks Mo

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