The principle of braking is very simple – to slow down a particular object by converting the kinetic energy into heat and light. F1 cars have disc brakes (like most road cars) with a rotating disc (rotating with the wheels) squeezed by brake pads with help of hydraulic piston caliper. In that process speed of the car turns into a large amount of heat and light.
In the same way that too much power makes rear tyres slip, too much braking force cause the wheel locking because maximum amount of avalaible grip is exceeded. As systems that prevent the wheels from locking during braking are not allowed (ABS), braking remains one of the most important test of skill for drivers which is particularly evident on tracks with a lot of hard and long braking zones like Montreal and Monza.
FIA Technical Regulations allow each car to have a double, circular hydraulic brake system with two separate fluid tanks for the front and rear wheels. This ensures that braking is possible even if one of the systems fails.
The distribution of braking force between front and rear wheels can be controlled from cockpit which directly affects the behavior of the car when braking. Drivers also adjust brake balance depending on amount of fuel in the car which affects not only weight, but also weight distribution and centre of gravity.
Normally, 50-60% of the braking force is on the the front wheels during braking, because the inertia shifts weight forward. By changing the balance of braking driver affects the behavior of the car on braking, brake and tire wear which is especially important in the race. Adjusting brake balance can be very usefull in qualifying too as driver can adjust car braking and corner entry balance fot each specific corner.
Formula 1 uses advanced materials for its braking system which have superior weight and thermal properties compared to materials used on most road cars. All F1 cars use carbon brake discs and pads which weight much less than steel discs and pads used on road cars and in some other racing series and have superior cooling capacity.
Typical F1 disc weighs about 1 kg (for comparison steel disc used in American CART series weighs 3 kg) and special brake pads can withstand temperatures above 1000 ° C. Previously, teams used different discs for qualifying and race, but the rules changed in 2003. when Parc Ferme was introduced so they had to run same brakes for qualifying and race.
Formula 1 brakes are extremely effective. In combination with modern and advanced tyre compounds braking distances decreased dramatically. Formula 1 car needs shorter distance to stop from 160 km / h than the road car from 100 km/h. The brakes in Formula 1 are so good that the rules deliberately slow down their development to prevent even shorter braking distances which would make overtaking even harder.
Formula 1 car needs less than four seconds to stop from 300 km/h and less than three seconds from 200 km/h. Numbers depend on suspension settings, tyre compound, asphalt and its temperature, weight distribution, centre of gravity, fuel load, downforce levels…
Since 2009. F1 cars (or at least some of them) have KERS (Kinetic Energy Recovery System) which captures kinetic energy and turns it into electric power stored in battery or flywheel.
KERS no longer exist from 2014. because ERS (Energy Recovery System) was introduced. Complex new system have two motor-generator units which combines energy recovery from rear brakes (MGU-K) and exhaust gases (MGU-H).
Construction and materials
As in every braking system used in road cars, the central part of the brake system is brake disc that rotates with the wheel. When the driver presses the brake pedal, brake fluid enters the cylinders, brake pistons and carbon brake pads squeeze rotating disk which slows down disc and the car itself. Kinetic energy (half the product of the mass and the square of velocity) is converted into heat and light.
Brake fluid is located in the two main cylinder located behind the place where the monocoque connects the nose of the car. They are located between the parts of the suspension in order to save precious space in that area of the car. The main brake cylinders contain brake fluid for the front and rear brakes and systems for front and rear brakes are separated in order to meet the technical regulations. Therefore, if one of the systems fail, driver can stop the car using another system.
Although very strict rules keep braking system design relatively simple, brakes are still one of the more expensive parts of Formula 1 cars. Brake pads and discs are made from high quality carbon material (ie. carbon – carbon) that are significantly different from those used in other parts of the car. It is characterized by a high friction coefficient essential for achieving the greatest possible braking force.
Formula 1 teams currently use three different brake material suppliers: Hitco, Safran (Carbon Industrie) and Brembo.
In 2010. refuelling was banned and cars had to start with a lot of fuel which made life difficult for brakes. Situation became even more challenging in 2014. when minimum weight was increased from 642 to 691 kg. Energy recovery system, also introduced in 2014., slows the car down when in harvesting mode so rear brake discs can be thinner and smaller in diameter, just as rear calipers and rear brake ducts. Maximum allowed disc thickness is 28 mm, but from 2014. teams often use thinner 25 mm discs at the rear.
There are currently three manufacturers of brake calipers in Formula 1 – Brembo, AP Racing (part of Brembo Group) and Akebono which currently supplies only McLaren. The fourth company Alcon has the capability to design and produce brake calipers for an F1 car, but according to official technical specifications neither team is using their products.
Key elements of the brake calipers are weight and strength. The teams work closely with brake caliper manufacturers to achieve exactly what they want for each race. Although all calipers are similar, their position relative to the disc is not. Positioning at the bottom lowers the center of gravity, but hampers the supply of brake fluid.
Since 2014. rear brake calipers have a different role than before due to the impact of the ERS system on brakes and electronics which controls the rear brake pressure in order to preserve stability. While the driver is braking, electronic controller enables high-pressure hydraulic system to maintain braking force to the rear axle giving driver more constant feeling on braking.
Keeping it cool
Brakes turn kinetic energy to heat thanks to high friction coefficient between discs and pads so heat management plays crucial role in effectively using brakes during the race. But brakes can be too cold too…
In cool conditions and on long straights brake temperature can drop too much which leads to high temperature difference at the start and the end of braking zone. Being out of their operating window, brakes have reduced stopping potential and increased wear which is something drivers want to avoid.
The brakes are cooled by directing air from the brake duct through the openings of the disc and on its surface. Most often smaller cooling intake cools the brake calipers and larger directs air toward the center of the disc, which is expanded outwards through the holes in the disc and exits through the rim.
The amount of air entering the brakes is controlled by the size od brake ducts so teams use largest ducts in Montreal and much smaller ducts on tracks like Spa and Silverstone. The higher intakes mean higher drag, but less downforce too because the part of the airflow that would otherwise generate some downforce end up in the brakes. Also, the reason to use the smallest ducts possible is not only driven by aerodynamic needs – they are used to keep the brake temperature on tracks that do not have so much braking or in cool weather conditions.
In recent years, brake discs have up to 1,000 tiny holes which increase cooling capacity and reduces wear and teams are constantly pushing the limits in this area. Mercedes even tried concave disc edge on their W07 Hybrid to increase the surface and cooling capacity.