F1 Braking Secrets – Calipers
Often made in a single block, the stirrups are made in close collaboration with the teams, with absolute confidentiality in mind. Section is important!
AROUND THE DISC: BELT AND BEARING
The disc, whose secrets we revealed in episodes 1 (discs) and 2 (holes) of this series, is attached to its hub by a metal ring called a “belt”.
Designed by the team or the disc supplier, this part must be precisely machined to allow the transfer of very large torque during hard braking without weakening the disc or belt. Incredibly stiff, this part nevertheless features a number of perforations for hot air evacuation (from 2019 to 2021, these were mainly used to blow hot air outwards for aerodynamic purposes).
A hub-and-belt-filled disc at its center is surrounded by a complex network of tubes and ducts that carry the air trapped by the brake rods into the tire (since blowing out is prohibited).
BRAKE IN COLLABORATION WITH TEAMS
Multi-role scoops front and rear direct cool ambient air into the braking system to cool the discs, pads and calipers.
Determined by the current technical regulations, their dimensions and shapes are calculated by the engineers of each team together with the disc supplier in order to obtain an air flow capable of cooling the disc without overheating. It has a negative effect on aerodynamics.
“We design discs knowing that they are integrated into the complete braking system (shells, channels…), to explain F1 Giovanni Clemente, race engineer at Brembo, which supplies the vast majority of teams. We use CFD to visualize the airflow around the disk.
“We exchange hundreds of 3D CAD files with our client teams to find the best solution. These relationships require a great deal of trust and full respect for confidentiality. Everything should be divided into sections.
“In short, the team sets energy and power levels to break down. It is up to us to find the best way to achieve this with them. We offer the team several iterations until we find the most satisfactory solution.”
“We provide the tools, we offer our recommendations, but the team is free to make their own choices, whether they prefer cooling the disc or the calipers, the wheels, etc.
Brake cooling occurs mainly in a straight line when high speed allows large volumes of air to flow through the buckets. This is why Monaco, with its very short straights, is demanding in this area despite its low speed.
Stirrups IN ONE BLOCK…
Customization also applies to the calipers, which are one of the important components of the braking system.
When the driver presses the left pedal, its pressure is transmitted through the hydraulic system to pistons located in the calipers of each wheel, which in turn transmits this pressure to the pads that “pinch” the disc for braking.
According to the rules, each wheel can have only one caliper with a maximum of six pistons. All four calibers must be made of aluminum alloy. At Brembo (which supplies most of the teams) they are made from one piece, meaning they are mass cut from a block of aluminum and lithium combined. Each stirrup weighs between 1.5kg and 2kg.
Inside the caliper, pistons press the pads onto the discs. To hold the pads in place, holes are drilled inside the pad into which three pistons go (see yellow line below).
Using the same Finite Element Analysis method used to build the chassis, engineers managed to reduce the weight of the part while maintaining its stiffness. Holes are drilled in the stirrup to make the part lighter and to facilitate its cooling (it can heat up to 200°C).
For advanced training, the supplier’s engineers design a custom model with the exact stiffness/weight ratio the team wants.
Some teams prefer lighter but less stiff calipers, while others prefer stronger but heavier models with caution.
… AND BIGGER
The increase in the diameter of the discs at the front forced the engineers to change the corresponding caliper:
“The change ahead means you have to draw new calibers, Brembo team manager Andrea Algeri confirms. “Because there’s more space at the wheel, we can play in some pretty weird formations.”
“Because the caliper is larger, the master cylinders also need to be resized based on input from our various customers.”
These changes prompted teams to change the position of the stirrups on the front end. Traditionally, these are mounted below or slightly behind the dial (ie at 6 o’clock (bottom) or 9 o’clock). [à trois quart vers l’arrière]). Interestingly, some teams have mounted the front calipers in the forward position (ie at 3 o’clock), such as Alpine on the A522 and Aston Martin on the AMR22, as seen in the image above.
FOUR OR SIX PISTONS
Since 2014, calipers can have fewer than six pistons at the rear. As the Kinetic Energy Recovery System (MGU-K) provides a certain amount of braking, conventional brakes are under low stress at certain speeds. If they are still required in the initial phase of braking, the rest of the deceleration can be taken up by the MGU-K.
“The maximum number of pistons is six, that’s right, Defines Clement. But to reduce weight, we could only have four in the back, because energy recovery plays its part in slowing down the axle and ‘shrinking’ the discs.”
Opting for four pistons saves a few grams, but changes effort and cooling requirements…
DRAG IN COSTS
In 2021, over one season and two cars, Brembo supplied each team it supplied with 10 sets of calipers (ie forty calibres), 140 to 240 discs and 280 to 480 pads, depending on the team’s budget.
Since 2022, teams have used slightly less:
“Brembo can compete in several Grand Prix with one disc. Andrea Algeri (Brembo) explains to our colleagues on the site Competition. Our attrition rate is low. We were also in favor of a limit to a single set of discs and pads per Grand Prix – this was ultimately rejected.
“In any case, teams order a little less discs than we do, because the bigger discs last longer, but also because they have to pay attention to their budgets.”
By introducing financial regulation, the FOM and the FIA stepped in to control the costs of the teams. It was necessary to stop the escalation of budgets.