How a sandwich wrapper can “take out” the brakes on a Formula 1 single-seater

4/19/2021

Because Formula 1 single-seater brake ventilation is such a delicate aspect.

Each Formula 1 single-seater car is the result of thousands of hours of research, countless computer calculations, simulations and tests, not to mention several sessions in the wind tunnel, necessary for optimizing everything, down to the smallest component. Braking systems are no exception where this is concerned and Brembo subjects all the components of the braking systems supplied to the Formula 1 teams to rigorous and highly sophisticated tests and simulations.

However, in spite of all calculations and static and dynamic tests, racing history is rife with unexpected events generating unforeseen problems, thus compromising a good Grand Prix result. In most cases, the triggering event was an external factor, independent of the team, such as a part that came off of another single-seater, for example.

On the other hand, sometimes faults have been caused by factors that have nothing to do with the other cars on the track, such as an animal or even an object from the stands that made its way onto the track. Alpine Renault knows a little something about this, as they had to stop Fernando Alonso after only 33 laps in the Bahrain GP to avoid any worse damage to his A521.

A sandwich wrapper was entirely to blame when it got stuck in the car’s rear brake air intake, generating an amount of overheating that ended up impairing the operation of the braking system. The pit crew realized that something wasn’t quite right as they watched the telemetry and they opted to withdraw, because continuing would have endangered the safety of the driver and that of his rivals.

F1 history and Alonso himself are no strangers to episodes like this one. In 2015, during the Spanish GP with McLaren, Alonso was also forced to abandon the race in the 25th lap, after a few terrifying moments – “the rear brakes didn’t seem to work anymore” he had reported to the garage. The malfunction was caused by a visor tear-off that had made its way into the brake duct. The small piece of transparent plastic was found on the bottom of the car. And two years ago, for the same reason, Carlos Sainz had to make an unscheduled pit stop during the Canadian GP, once again because of a visor that ended up in the brake duct, making temperatures rise beyond operating range.

Thanks to the multiple sensors located in various points of the single-seater, hundreds of physical parameters are read and their values are transmitted to the garage in real time. The data is naturally encrypted so that each team only gets its own and not that of the competition, too.

Using the sensors, the teams know the temperature of the discs and calipers at any given time. Based on this data, the driver may be notified in order to make changes to the single-seater’s brake balance or the way the system is being managed. This communication takes place when unexpected abnormalities occur.

The importance of the brake air intakes

But how do the brake air intakes work and what happens in the event of accidental obstruction?

Over time, increasingly more sophisticated carbon ducts have been developed around Formula 1 car wheels with air intakes, flaps and custom-designed flow deviators capable of both cooling the braking system and performing aerodynamic functions. This is because, by removing the turbulence generated by the rotating motion of the tire, the forward resistance of the single-seater can be reduced or the aerodynamic load increased.

If even one of the air intakes is obstructed, the disc and pads must work constantly at higher than optimum operating temperatures. This results in their oxidation and within just a few intense braking operations, the friction material’s temperature would soar rapidly.

The accidental lack of adequate ventilation could therefore create critical conditions, first for the brake fluid and then for the friction material.

In addition to wearing extremely quickly, the friction material would begin to burn, eroding part of the disc, while the brake fluid would begin to boil, generating the vapor lock effect. If the single-seater were to continue lapping, meaning that the driver would continue to press the brake pedal, the wear would reach the ventilation holes and ultimately take the disc to explosion-risk conditions.

The brake calipers are more stable because the aluminum they are made of melts at 700 °C (1,292 °F). Brembo 6-piston calipers have a guaranteed threshold of 210 °C (410 °F), lower than the minimum operating temperature for the discs, which have a range of use between 350 °C (662 °F) and 1,000 °C (1,832 °F).

Unlike discs and pads, which also reach extremely high temperatures in the most extreme use such as the Canadian GP, where the layout includes a lot of braking sections, all decisive and very close together, Brembo calipers never exceed 200 °C (392 °F) .

The optimum temperature conundrum

On the Gilles-Villeneuve circuit, as well as on the Abu Dhabi, Mexico City and Singapore tracks, the role that brake air intakes play becomes fundamental because the sequence of violent braking sections without adequate distances to let the braking systems breathe (in other words, long straights) demands the internal redirection of large quantities of air.

On the contrary, on tracks like Silverstone, Suzuka or Interlagos, an opposite risk exists, namely that the brakes will not reach the ideal operating temperature, resulting in the potential for a glazing effect of the friction material. In conditions like these, the brakes need less air and the air intakes are “choked”, effectively reducing the airflow to the brakes.

On paper, these choices appear to be entirely logical, but cornering in a Formula 1 car involves many elements, each with needs that differ from the others. Furthermore, the impact on tire performance must also be considered, as well as the operating temperature of the power unit and resistance to forward motion on the straights.

In short, a true balancing act, to which yet another variable is added: The number of brake disc ventilation holes. Designed using a CFD (Computational Fluid Dynamics) calculation, these are the result of synergistic development between the disc manufacturer and the single-seater manufacturers.

Based on the air intakes being used during a season or modified for a certain GP, the teams choose the disc version they feel is best. For the front, Brembo offers the Very High Cooling alternative with 1,480 holes, the High Cooling alternative with 1,250 holes and the Medium Cooling alternative with 800 holes.

For each of these, the teams can also choose the variant with machining on the outer diameter of the disc, the “groove”, which creates an air divergent section and increases the material cooling efficiency. For the rear, on the other hand, Brembo offers two-disc options: High Cooling (1,250 holes) and Medium Cooling, with 800 holes