# Brakes

The beginning of this article will be a bit boring, but is important to discus all of this to be able to understand the brakes!

Brakes are designed to slow down your vehicle but probably not by the means that you think. The common misconception is that brakes squeeze against a drum or disc, and the pressure of the squeezing action is what slows you down. This is only part of the reason you slow down.

Brakes are essentially a mechanism to change energy types. When you're travelling at speed, your vehicle has kinetic energy. When you apply the brakes, the pads or shoes that press against the brake drum or rotor convert kinetic energy into thermal energy via friction. The cooling of the brakes dissipates the heat and the vehicle slows down. This is all to do with The First Law of Thermodynamics, sometimes known as the Law of Conservation of Energy. This states that energy cannot be created nor destroyed, it can only be converted from one form to another. In the case of brakes, it is converted from kinetic energy to thermal energy.
Because of the configuration of the brake pads and rotor in a disc brake, the location and Angular force of the point of contact where the friction is generated also provides a mechanical moment to resist the turning motion of the rotor.

If you drive a car long way down the hill, you're probably familiar with the term brake fade which is used to describe what happens to brakes when they get too hot. By the First Law of Thermodynamics, as you start to come down the hill, the brakes on your vehicle heat up, slowing you down. But if you keep using the brakes, the drums or discs and brake pads will stay hot and get no chance to cool off. The next time you try to brake, because the brake components are already so hot, they cannot absorb much more heat.
In every brake pad there is the friction material which is held together with some sort of resin. Once brake pads starts to get too hot, the resin holding the pad material together starts to vaporize, forming a gas. That gas has to have somewhere to go, because it can't stay between the pad and the rotor, so it forms a thin layer between the two trying to escape. The result is very similar to aquaplaning while going too fast in the rain; the pads lose contact with the rotor, thus reducing the amount of friction. This is a brake fade.
As the brake components cool down, their ability to absorb heat returns, the pads cool off which means they have more chance to heat up again before the resin vaporizes, hence the next time you use the brakes, they seem to work just fine.

So how do the engineers design brakes to reduce or eliminate brake fade? For older vehicles, you give that vaporized gas somewhere to go. For newer vehicles, you find some way to cool the rotors off more effectively. Either way you end up with cross-drilled, grooved or vented brake rotors. While grooving the surface may reduce the specific heat capacity of the rotor, its effect is negligible. The rotors will heat up to cool down no faster or slower. However, under heavy braking once everything is hot and the resin is vaporizing, the grooves give the gas somewhere to go, so the pad can continue to contact the rotor, allowing friction and allowing you to stop.

How does it apply to bigger brake rotors; a common sports car upgrade? Well sports cars and race bikes typically have much bigger discs or rotors than your average family saloon car. The reason again is to do with heat and friction. A bigger rotor has more material in it so it can absorb more heat. More material also means a larger surface area, which as well meaning more area for the pads to generate friction with, also translates to better heat dissipation. On top of that, the larger rotors mean that the brake pads make contact further away from the axle of rotation. This provides a larger leverage and mechanical advantage to resist the turning of the rotor itself.
That explains the whole principle behind why bigger rotors = better stopping power.
Taking it one step further, carbon or ceramic brake rotors, as found on high-end Ferraris, Porshes or McLaren F1 road cars, and Formula-1 race cars, are even better again at heat transfer.

The whole understanding of the conversion of energy is critical in understanding how and why brakes do what they do, and why they are designed like they are. In Formula 1 car, you'll see the front wheels have huge scoops inside the wheel pointing to the front. This is to duct air to the brake rotors to help them cool off because in Formula 1 racing, the brakes are used viciously every few seconds and spend a lot of their time trying to stay cool. Without some form of cooling assistance, the brakes would be fine for the first few corners but then would fade and become near useless by half way around the track. Another reason for this scoops in F1 case is that rotors are working on very high temperature of around 800-1000 C, and without additional venting this heat will be transferred to wheels and tires with negative effect to stability of metal and rubber.

##### An important note about drilled rotors (www.carbibles.com): Drilled rotors are typically only found (and to be used on) race cars. The drilling weakens the rotors and typically results in micro fractures to the rotor. On race cars this isn't a problem - the brakes are changed after each race or weekend. But on a road car, this can eventually lead to brake rotor failure - not what you want. I only mention this because of a lot of performance suppliers will supply you with drilled rotors for street cars without mentioning this little fact.

Now when we clear the physics of braking, Let's talk about F1 brakes.

To be quick in terms of lap time, you need to be good at stopping. It sounds odd but it's true. At some venues almost a quarter of the lap is spent pushing on the brake pedal.
Unsurprisingly, both Monaco and Singapore require the most use from the brake pedal, with 23% of their respective laps spent under braking. The Hungaroring is the next with 22%, while Mexico and Shanghai both require 21% of the driver's time to be spent using the brakes. Spa and Monza require the least amount of time on braking, requiring just 12% each of the lap spent under braking. As a result, Monza requires the most effort from the brakes, sustaining an average deceleration of 5.5g – almost 0.9g higher than Sochi, the next most demanding circuit. The peak deceleration of the season was that produced at the final chicane at Montreal at 5.6g. In particular, the Parabolica creates a maximum deceleration of 6.6g, where the driver exerts a maximum load of 232kg on the brake pedal to reduce the overall stopping distances. (Data released by Italian brake manufacturer Brembo for year 2017.)

Disc brakes are an order of magnitude better at stopping vehicles than drum brakes, which is why you'll find disc brakes on the front of almost every car and motorbike built today. Sportier vehicles with higher speeds need better brakes to slow them down, so you'll likely see disc brakes on the rear of those too.
Formula 1 use disc brakes. They consist of a rotor and caliper at each wheel. Expensive carbon-carbon (the same material used on the Space Shuttle) composite rotors - introduced by the Brabham team in 1976 - are used instead of steel or cast iron because of their superior frictional, thermal, and anti-warping properties, as well as significant weight savings. Strangely ceramic discs have not been a development seen at races. Rules limit the diameter and thickness of discs, but no other regulatory restrictions are placed on these parts.
These brakes are designed and manufactured to work in extreme temperatures, up to 1,000 degrees Celsius, but carbon brake discs work properly at between 300 and 800 degrees Celsius. Below that they don't have any stopping power; above it and the wear rate of the carbon increases dramatically with temperature.

Formula 1 cars and indeed all race cars, have two independent brake circuits (front and rear) which come together at the brake pedal. A pivot on the pedal apportions pedal load to the twin master cylinders, according to the position of the pivot on the crossbar that links the pedal to the master cylinder pistons.

Brake balance or brake bias is controlled from F1 cockpit, controls on steering wheel. Stronger front brake balance causes the front of the car to dip more than the back, that is, more weight transfers to the front wheels.
Apart from having greater stopping power, it allows better tire contact to allow the car to steer into the corner while under brakes. Stronger rear brake balance, will cause the rear wheels to lockup slightly (dependant on how strong you set balance) when the weight transfers to front during braking. Causing slight oversteer. Not a bad thing, because you might want to induce a bit of oversteer in heavily understeering cars. Too much front brake bias and the front tires will lockup, causing severe understeer, which isn't good. And too much rear brakes can cause the back to lockup causing severe oversteer and spin.
As you can see there is a cause and effect for each setting. Too much or too little of a setting will cause undesired effects. Too much front brakes and the tires lock causing understeer. Too little, and the car doesn't stop fast enough, causing the car to continue its momentum straight ahead.

An average F1 car can decelerate from 100-0 km/h in about 17 meters, compared with a 2007 Porsche 911 Turbo which takes 31.4 meters.

When braking from higher speeds, aerodynamic drag enables tremendous deceleration: 3.5 g to 4.0 g (44.1 to 49 m/s2), and up to 5.5 g at the high-speed circuits such as the Autodromo Nazionale Monza (Italian GP). This contrasts with 1.0 g to 1.5 g for the best sports cars (the Bugatti Veyron is claimed to be able to break at 1.3 g). An F1 car can brake from 200 km/h to a complete stop just 2.9 seconds, using only 65 meters.

There are three companies who manufacture brakes for Formula One. They are Hitco, (based in the US, part of the SGL Carbon Group), Brembo in Italy and Carbone Industrie (part of Messier Bugatti) from France. Whilst Hitco manufacture their own carbon/carbon, Brembo sources theirs from Honeywell, and Carbone Industrie purchases their carbon from Messier Bugatti.

F1 brake disc was 278 mm in diameter and a maximum of 28 mm thick. After big aero regulation changes 2017, and because of higher speed and loads maximum thickness was changed to 32mm. Also, brake pad thickness was changed from 6 to 8mm. The carbon/carbon brake pads are actuated by 6-piston opposed calipers provided by AP Racing or Brembo. The calipers are aluminum-lithium alloy bodied with titanium pistons weighting approximately 2 kilograms and costing well over 7000\$ a piece. The regulation limits the modulus of the caliper material to prevent teams using exotic, high specific stiffness materials. Titanium pistons save weight, but also have a low thermal conductivity, reducing the heat flow into the brake fluid.

The manufacture of brake friction material begins with same basic fibre as that used in the production of the carbon fibre fabric from which racecar chassis are made – PAN (polyacrylonitrile). It is, however, processed in a wholly different way, being passed through carbon deposition and high-temperature oxidation stages lasting several weeks that transform its molecular structure and result in a material that as well as offering lower weight relative to metal brakes provides greater durability and higher thermal capacity. These gains were not without cost though, and a long development was necessary to provide sufficient cooling of the discs, pads and calipers and other parts in their vicinity before the use of carbon brakes became practicable.

Disc and pad material varies according to their manufacturer. It is also tuned for each race track and even for each driver. Additionally cooling patterns will vary from track to track. In Melbourne or Hungary, for example, we can see the high density drillings across the disc. With Melbourne or Hungary being heavy on braking the pads are also drilled in attempt to keep the brake system cool.

###### Examples of few differently drilled brake discs ventilation holes . Top left picture shows Ferrari flat directionaly drilled holes. Holes point from outside directly to center of the disc. The holes are formed of three holes merged into one. Same situation is with Red Bull Racing disc brake on picture top right. Different logic show Mercedes with disc drilled with 4 rows of smaller holes drilled directionaly. Marusia, on picture down right, use two rows of bigger holes drilled tangentially. Number of holes in 2017 was risen to approximately 1400 holes. Pictures from scarbsf1 blog By Craig Scarborough.

Brakes and pads wear at an equal rate, so the few millimeters gap in between disc surface and drillings is all the wear these parts will see, before catastrophic failure. As wear increases with temperature there are sensors measuring the disc surface temperature and also wear sensors for both the inner and outer pads.

To monitor all the functions on the brakes, there will be an array of sensors fitted to the parts (visible at picture below). On upper picture you can see 3 round connectors on RedBull front brake caliper. These are all connected back to the main ECU, rather than cabling for each sensor passing through the wishbones to the cars main wiring loom, there is a hub fitted to the upright that collects all he signals and passes them back via a single cable. This Hub Interface Unit (HIU) is a common part supplied by MES to all the teams. It has inputs from the aforementioned Pad wear and disc temperatures sensors, as well as two wheel speed sensor (two in case one fails), also a load cell for measuring pushrod (or pullrod) loads.

Some interesting facts:

4 seconds is the amount of time it takes for a Formula One car to go from 300km/h to a complete halt.

At 200 km/h, a Formula One car requires just 2.9 seconds to stop completely, in only 65 meters.

At 100km/h, these values are incredible: 1.4 seconds and 17 meters!
Under these heavy braking periods, a driver is subjected to a horizontal deceleration of close to 5,2G.

Brake disc is made of carbon/carbon composite, and working temperature is over 1000°C during braking.

At Albert Park (Australian GP), during second corner braking, Formula 1 can develop 4,6g of load and developed power of 1855 Kw (1,855Mw).

"The use of carbon-fibre brakes requires a little time to get used to," states Jarno Trulli. "In fact, during the first milliseconds after pressing the brake-pedal; it feels like nothing is happening." This delay is in fact the length of time required by the disk/caliper tandem to reach operating temperature, which increases by 100°C per tenth of a second for the first half-second of braking, after which it can reach up to 1200°C. After that short period, deceleration is immediate, and brutal.

###### Used carbon brakes and brake pads

Check out my article about new Formula 1 Brake by Wire brake system.

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January 14, 2018 at noon, aged 86, died Daniel Dan Sextorn Gurney, a racer, a team owner, a car manufacturer and a sage, American racing legend, a man who won four F1 grands prix in his 86 starts, the 24 Hours of Le Mans in 1967 and five NASCAR races. He also won races in CanAm and TransAm. He won 1967 Belgian Grand Prix driving an Eagle-Weslake, a car of his own creation, for me most beautiful F1 car ever (on my banner). In F1 circles, there was only one Dan. The American is also credited with the spraying of champagne on podiums and creating the "Gurney flap" aerodynamic device. In 1968, he became the first driver to use a full-face helmet in a grand prix. He is survived by his second wife, Evi Butz, sons Justin, Alex, Daniel Jr, John and James, and a daughter, Lyndee and by eight grandchildren. RIP Dan and thank you for everything. Godspeed.

- f1technical.net, a great site with a lot of technical information’s and explanations. Site is updated daily with news from F1 word.

- autosport.com, This site is a legend. A bible for racing lovers. News from all around the word. Unfortunately, to get access to all news, interviews and to open the site completely you should be subscribed to Autosport magazine. Anyway, great read.

- JA.F1 site (or blog) ovned by ITV Sport’s lead commentator on Formula 1 James Allen

- joesaward is the Joe Saward official blog about Formula 1 world. Joe is an journalist, who write primarily about politics in and around motorsport, specifically on the FIA Formula 1 World Championship

- vitalf1.com/ is another great site for Motor Sports fan’s like me. Site is relatively new, but great fun, with great discussion forum, Formula 1 news and forum.

- f1.gpupdate.net, Site with fresh news from Formula 1

- planetf1, another site with many different articles, news and statistics. Biased toward British teams, but anyway good read.

- gurneyflap.com, Great history site. You can learn a lot from this site. Pictures, cars and many many more. Great.

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4ormula1 is a database of Formula 1 history and statistics of drivers, teams, grand prix, and all results since 1950.

Enjoy range of Podcasts and Articles on Motorsport. Every week a Formula one chat on Missed Apex F1 Podcast with F1 journalist Joe Saward and tech Analyst Matthew Somerfield as guests. Also the exciting all electric racing series formula E on eRadio Show and Bike Show Lean Angle Podcast.

-Racecar Engineering, an online magazine with a lot to learn from, a lot of technical information’s and explanations

- fia.com, La Fédération Internationale de l'Automobile, representing the interests of motoring organisations and motor car users. Head organisation and ruler in auto sport.

- wikipedia.org, I don’t believe that I have to tell you anything about this site. It’s not about Formula 1 technology, but you can learn a lot about that too.

- carbibles.com, a great site for normal car users. Here you can find explanations of almost everything about your car and how it works. Technical reviews and explanations of some in-car gadgets.

- Daretobedifferent.org Susie Wolff and UK governing body of UK motorsport have joined forces to launch Dare To Be Different, a high-profile new initiative which is about increasing female participation, not just on the track but in all aspects of the sport.