2. Maintaining the Optimal ‘Operating Window’

The carbon braking system has a narrow operating range to function correctly (usually between 350 °C and 550 °C). For this reason, Brembo engineers’ task is not only to prevent overheating but also to counteract undercooling:

• Avoiding Undercooling: Temperatures that are too low (below 350 °C) drastically reduce the friction coefficient and, consequently, braking torque.

   

• Variable Aerodynamic Management: The size and geometry of the air intakes are constantly modified and adapted (often partially covering the openings with special tapes) depending on the circuit, aerodynamic load, and environmental conditions, in order to keep the brakes within the optimal thermal window throughout the race.

Designing the Internal Ventilation Channels of Brembo Carbon-Carbon (C/C) Brake Discs Is a High-Precision Engineering Task That Relies Heavily on Computational Fluid Dynamics (CFD).”

1. The Primary Goal of CFD: Uniform Thermal Control
 

In a C/C disc, the objective is not simply cooling, but also controlling temperature to ensure friction is distributed evenly.

• Maximizing Mass Flow: CFD models the air entering the ducts and distributes it inside the disc, aiming to ensure that the largest possible volume of fresh air passes through the internal channels while minimizing pressure drop.

   

• Uniform Temperature Distribution: The main technical challenge is differential thermal stress. CFD simulates detailed thermal maps to achieve the most uniform heat dispersion possible—an essential factor in preventing cracks or uneven wear of the disc.

The Evolution of Brake Discs Is Clearly Visible to the Naked Eye: To increase the airflow dedicated to cooling, Brembo engineers have progressively increased the number of radial ventilation holes while simultaneously reducing their size.

More than twenty years ago, Brembo carbon discs featured a maximum of 72 holes: they were arranged in a single row, and each hole had a diameter exceeding one centimeter. Thanks to these discs, in 2002 Michael Schumacher won the World Championship with 11 victories and 17 podiums in as many GPs.

Within just a few years, as research advanced, the triple-digit mark was reached for the first time: in 2006, discs featured 100 holes, smaller and with the distinctive ovoid shape, then considered the ideal solution.

The 2007 regulations introduced new constraints: disc diameter set at 278 mm, maximum thickness of 28 mm, cooling allowed exclusively through air, and a ban on extending the system beyond the rear part of the wheel. These limitations pushed Brembo engineers to focus even more on improving cooling efficiency.

By 2008, considering the 28 mm thickness limit, a new ventilation pattern was introduced: the holes were arranged in two adjacent rows with a shared section, creating a series of elements resembling an inverted ‘8’. In addition to the new design, the total number doubled, reaching 200 holes per disc.

In 2010, once refueling during races was banned, fuel tank sizes increased and, consequently, the minimum weight of single-seaters rose from 605 kg to 620 kg. Studies on the braking system were revised to ensure a high standard of efficiency both for light cars and fully loaded ones, and as a result, the number of holes became less of a priority.

Two years later, the FIA banned the use of blown diffusers, reducing rear aerodynamic load. As a consequence, brake balance shifted even more toward the front axle, and to handle the increased stress without risking overheating, Brembo multiplied the number of holes.

Thanks to Computational Fluid Dynamics (CFD)—the study of fluid dynamics through computer simulations—and advancements in carbon machining, in 2012 the number of ventilation holes per brake disc rose to 600, with the introduction of a third and fourth row of holes, reducing their diameter and eliminating overlapping that reduced the surface exposed to airflow.

In 2013, taking advantage of substantial regulatory stability, Brembo introduced a new type of carbon for its discs: compared to the previous CCR, CER ensured maximum speed in reaching operating temperature, a wide usage range, and a very linear response.

Even during the regulatory revolution of 2014, Brembo was well prepared. That season saw the return of turbo engines, absent since 1988, but displacement was limited to 1.6 liters and rotation to 15,000 rpm. Additionally, hybrid technology was introduced through two electric motors, and the minimum car weight increased from 642 kg to 691 kg.

The significant increase in mass required a redesign of the braking system, also due to the introduction of Brake-by-Wire. Nevertheless, this was accompanied by further improvements in ventilation, with the number of holes per disc surpassing one thousand.

In 2016, for the first time, the push toward design extremization allowed reaching the record threshold of 1,100 holes per disc. This marked the prelude to a new challenge, as in 2017 the width of the cars returned to 2 meters, increasing by 20 cm in one step. The width of the front wing and tires also grew, resulting in greater performance, including a 25% increase in braking torque.

The regulations took this performance increase into account and raised brake disc thickness from 28 mm to 32 mm. The greater thickness allowed for a further increase in ventilation holes, leading to another evolution in the cooling system. Thus, starting from the 2017–2018 biennium, each disc featured 1,260 holes.”

However, teams could choose among three different Brembo disc solutions, depending on the expected temperatures during each Grand Prix and the race strategy adopted. This became even more evident in 2020 with the introduction of six carbon disc options, designed to cope with the continuously growing performance of power units.

For the front axle, teams could select between “Very High Cooling” discs, with 1,470 holes arranged in 7 rows; “High Cooling” discs, with 1,250 holes in 6 rows; and “Medium Cooling” discs, with 800 holes in 4 rows. For each ventilation type, a variant was also available featuring machining on the outer diameter—the so-called “groove”, which creates a divergent section on the outer part of the disc for additional aerodynamic benefits.

The six ventilation specifications for the front axle were reduced to just a couple with the latest regulatory change: the minimum car weight increased from 752 kg to 798 kg, aerodynamics changed, and 18-inch wheels replaced the previous 13-inch ones.
The new technical regulations also impacted braking systems, increasing disc diameter from 278 mm to 328 mm at the front and from 266 mm to 280 mm at the rear, while disc thickness rose to 32 mm compared to the previous season’s 28 mm.

The architecture changed as well: cooling holes on brake pads were banned, and a minimum diameter of 3 mm was imposed for holes on discs. This affected the total number of holes, which previously measured 2.5 mm in diameter, leading for the first time to a reduction in their overall count—from 1,470 in 2021 to the current 1,050.

A sort of “stop and go” in anticipation of another leap forward, expected next season, still in the name of thermal dissipation—the number one enemy of Formula 1.