WRC Braking technology


Solberg, WRC


Brakes are one of the most critical components on WRC racing car, and same stand for a tarmac or gravel events, and in slowing the car down play just as important a role in boosting overall speed. Quite apart from simply slowing the car, rally drivers use the brakes to position and balance the car on its approach to corners and to slide through tight hairpins whilst maintaining engine speed.
Each car's brake setup is also different for gravel and asphalt rallies, owing to the different demands and usage in each condition.

WRC braking disc

For an asphalt rally, the WRC car mostly use 366X24 mm 6 groove brake discs mounted to aerospace grade aluminium mounting bells at the front of the car and 305mm discs at the rear.
These are wrapped by eight-pot calipers with titanium pistons on fronts and four-pot variants at the rear. On asphalt there is generally more available grip than on gravel, so more force can be exerted through the brakes without the wheels locking, generating more friction. Speeds are also generally higher, leading to higher loads.


WRC disc brakes


As there is a lot of grip, you push the brakes quite hard so there is a lot of energy to dissipate in the brakes. There is a lot of heat being generated and the stages can be long. It is important that the temperatures do not keep going up and down and that they stabilize quite quickly. If the temperature keeps increasing the brakes will end up fading and losing power and performance. Running on tarmac means energy levels absorbed by the WRC brakes are considerably greater than those experienced during rallies on other surfaces.


Citroen WRC hybrid race car


Often, disc temperatures will reach extreme levels of up to 900°C (road car discs would not survive much above 600°C, at which point cast iron is starting to glow red). Tarmac pads for high performance WRC use are specially manufactured to offer possibly the highest temperature capability. Their unique formulation gives phenomenal bite and braking power, even at temperatures at which gravel rally pads either fade or start to deposit heavily on the discs, which can give rise to a loss of performance and consistency. Discs are often water cooled to improve efficiency.


Collection of WRC braking disc pads
Collection of WRC braking disc pads used by all WRC teams and considered as best racing products: Alcon-Prodrive, Ferodo, Mintex, Carbon Metallic, Endless, Pagid, Carbonne Lorraine, Pro Friction, AP Racing
Alcon Prodrive 6 pot water cooled caliper
Alcon Prodrive 6 pot water cooled caliper with 366 x 32 disc used in WRC, on the picture outer side of the grooved disc
Alcon Prodrive 6 pot water cooled caliper
Same as up, Alcon Prodrive 6 pot water cooled caliper with 366 x 32 disc used in WRC, on the picture inner side of the grooved disc. You can see suspension attachment points
Alcon Prodrive 8 pot water cooled caliper
Alcon Prodrive 8 pot water cooled caliper with 366 x 40 disc used in WRC, on the picture inner side of the grooved disc. You can see suspension attachment points.



The bigger discs and calipers enable more braking force to be exerted, slowing the car down more rapidly, and the increased surface area is more efficient as dissipating the resulting heat. Whilst the discs and brake pads are designed to work at a high temperature, there is an optimum level and overheating can lead to reduced performance. Never normally a consideration on the road, water jets can be used to cool the front brakes which can reach temperatures of 900°Celsius. The brake fluid temperature can also reach 120°Celsius.

There are two main reasons why bigger brakes are the key to getting more stopping power:


4 pot calipers Prodrive Alcon
WRC Brake 4 pot calipers Prodrive Alcon S4 - S10
6 pot calipers Prodrive Alcon
WRC Brake 6 pot calipers Prodrive Alcon S6 - S10
Brake 6 pot calipers AP-Racing
WRC Brake 6 pot calipers AP-Racing S11-on


























By contrast, the brake setup for a gravel car is typically smaller, owing to the facts that braking forces are reduced on the loose surface, and the smaller wheels used on gravel would not physically fit over asphalt brake discs. In these conditions, the front discs are 305mm racing items, coupled to four-pot calipers both front and rear. The rear brakes remain the same for both surfaces.


Prodrive WRC

On asphalt, the front brakes do the vast majority of the work in slowing the car down, so brake bias will tend to be set towards the front. Brake bias is the split of the braking force between the front and rear brakes. On gravel, the bias will be more towards the rear to help slide the car into the corners.

WRC Hydraulic handbrake system
Hydraulic handbrake system in two flavors. on the picture above you can see handbrake version mostly used in WRC (Prodrive WRC GD Impreza carbon handbrake). Other version showed on the lover picture is handbrake stick and sequential shifter in Mini WRC car for 2013..
Mini_WRC car handbrake


To help slide the rear on asphalt or gravel, the handbrake system is hydraulic and so very efficient. The lever is positioned where you'd expect a road car's gear stick to be, meaning that drivers can easily reach without moving their hand too far from the steering wheel. As with the rear brake setup, the handbrake is the same for both gravel and asphalt rallies.


To have a complete picture of performance driving, take a look at Corners, Setup, Traction circle, Using tires, Left foot braking, braking, advanced braking, Slipstreaming, drifting, cornering, shifting, Heel and toe driving technique and steering technique articles


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Books to read

Some useful links:

- 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.

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

Joe Saward blog
- 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

Vital F1
 - 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.

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

Planet F1
 - planetf1, another site with many different articles, news and statistics. Biased toward British teams, but anyway good read.

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

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

Racecar engineering
-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.

Sutton Images

grandprix photo

 - 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.

Dare To Be Different
- 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.