The Canadian Grand Prix is notoriously hot on brakes and teams will be keeping an eye on their temperatures this weekend - but how does an F1 car's braking system work and what can be done to make the most of it?
The Montreal circuit has a slippery track surface and is made up of long fast straights and slow chicanes, with only one corner taken at above 200km/h. This stop-start nature, coupled with the lack of grip, means it is the hardest circuit on the brakes all year, with six 'major braking events' on every lap.
This year the cars effectively have two different braking systems, with the traditional brake discs and callipers running alongside the KERS alternator motor system.
For those who don't know how the traditional system works, when the driver presses the brake pedal it releases brake fluid (located in master cylinders onboard in the car) to feed into the callipers which forces them to close around the disk and uses the friction of the two surfaces rubbing together to slow the car down, turning the kinetic energy of forward movement into waste heat energy.
KERS, meanwhile, converts the kinetic energy into electrical energy by spinning up an alternator that is connected into the rear wheel drivetrain. Different teams have different solutions for this, with Red Bull, for instance, understood to connect their alternator to the crankshaft of the engine via a clutch.
The KERS braking system does reduce the amount of work required from the traditional braking system, but because it can only charge (and release) up to a limited amount of energy over the course of a lap, it does not ease the workload on the traditional brakes that much.
When it comes to Montreal, then, the heavy braking requirements are still an issue.
The cars use separate front and rear brake systems, as stipulated by the FIA, mainly for safety but also to allow drivers to balance front and rear braking - which will be extremely important to also make the tyres last longer on the wear-heavy Montreal track, as drivers with fronts going off can move more braking force to the rears, and vice versa.
The brake discs themselves, which are 28mm thick and 278mm in diameter, are made of high quality carbon fibre and can take half a year to make using a process in which regular fibres are laid up in a sheet then heated, carbonised and left for weeks in hot ovens absorbing hydrocarbon-rich gas which merges the layers into one solid piece.
These brakes do actually need to be running at temperature to work well, with an ideal operating temperature of around 600 degrees. Below that, and the brakes are very unresponsive, but at around 1,000 degrees they become far too harsh and can wear down quickly.
The problem with Montreal is that there are few places where the brakes get a rest to cool down, so they will heat up and stay hot. The brake fluid will also heat up, causing problems with the braking efficiency.
Some teams run a different brake disc material for Montreal, one that allows them to run at a higher temperature without suffering too much wear (but one they would not use normally as it does not perform as well at lower temperatures).
They also all create special brake duct designs to Montreal to help bring more cooling air on to the brakes.
The brake ducts are mounted to the inside of the hub and aim to get as much cool airflow over the brakes as needed without having too big an opening - because the bigger the inlet, the more aero drag it creates.
Optimising the brake ducts is very important for all tracks, and teams use CFD, wind tunnels and brake dynamometer rigs to develop cooling techniques, creating different designs for different tracks depending on the level of braking (and therefore brake cooling) required.
These ducts have become incredibly complex in recent years, with independent openings to cool calliper and discs separately and large inboard feeding vanes that draw in a greater amount of airflow for a small amount of drag.
Red Bull has developed a complex internal design to feed the hot air from the discs and calliper out through the wheel using a drum-shaped duct with internal tunnels that run from the inboard area to the outboard area and out through the wheel spokes. Their wheels also have crafted spokes that improve airflow out of the braking system.
Teams have also started to use the external surface area of the brake ducts for aerodynamic gain by attaching turning vanes and small downforce producing elements.
This level of attention to detail shows just how much performance there can be in every part of the F1 car - and while the days of brake failure are relatively distant now, it is more about how efficient the teams can be with their cooling systems that can give them the edge, particularly in Montreal.
- brake discs