AP Racing - Brake Pads (Formula Student)
In most forms of motorsport the selection of brake pads takes up a lot of development time and testing. Teams/manufacturers will spend a lot of tack time evaluating and reviewing brake pad selection. However due to Formula Student cars having limited running time (most cars will only complete around 80-250km during their entire lifetime, where as a normal competition car will do that in a single day of testing) the choice of brake pads is less important to the overall performance of car.
Brake Pad Part Numbers
Brake pads part numbers are split into two sections. The first is the shape number, this tells us what the shape, size and (sometimes) thickness. Different pad manufacturers have different ways of laying out this section of the part number. This is important so that we know the pad will actually fit into the caliper. The second part of the part number tells us the compound. The compound is the material which makes contact with the disc. Different materials have different properties, some will stop the car quicker but may not allow for a more progressive speed reduction of the car.
Brake Compounds
Commonly we will look at several properties of the compound:
- Coefficient of Friction - This is the ratio of the frictional force between two surfaces. a value of 0.00 means that the two surfaces will not make an impact on each other, a value of 1.00 means that the surface which is moving will stop suddenly
- Longevity of the pad - How long the pad will last. For endurance racing we will prefer a pad that lasts longer, but this will often not be as agressive. The thickness of the pad also factors into this
- Temperature - The material will have it's best performance at a set temperature range, in most other forms of motorsport we will do a lot of research to find what temperature the brake pads are getting to (this is usually determined by the speed (energy) and weight (mass) of the vehicle
When we are helping teams choose the right compounds we will ask for the weight of the vehicle, the length of the sessions and if possible the temperature that the brakes get up too.
Formula Student CP4226 & CP4227 Brake Pads
The most commonly used calipers is Formula Student are CP4226 and CP4227, these both use CP4226D27 brake pads. These pads are available in the following compounds:
| Compound |
Material |
Average Friction |
Thickness of Material |
| APH420 |
SBS Organic |
0.39 |
7mm |
| RQ3 |
SBS Organic |
0.41 |
7mm |
| RX |
Sintered |
0.56 |
7mm |
| RCA |
No Longer Available |
| S30FF |
No Longer Available |
All of these pads for the CP4226 and CP4227 calipers have a total thickness of 27mm and the compound material is 7mm thick.
The APH420 compound will allow the driver to be more progressive on the brakes (allowing for smoother cornering speed). The RX compound will give a more aggressive stopping power allowing the car to stop in a shorter space. The RQ3 is a compromise between these two options.
Brake pads normally come in a box which contains 4 pads. Because these are actually normally used in motorcylces they are supplied in a pack of 2 pads. The cost of a pack of 2 pads is between £21.09 - £28.12 plus VAT.
Because Formula Student cars are unlikely to get up to the working temperature for the compounds we suggest that you don't get to distracted by trying to get the 'perfect solution' for compounds. We've put this piece together just to explain to you what is usually a very important issue but for Formula Student applications it's not that critical. We would always suggest that the pad compounds which are more readily available are the ones to go for as having the wrong compound pad is more useful then not having the perfect one.
Other Formula Student Brake Pads
If you are using calipers other then CP4226 or CP4227 then please contact us for more information on brake pad suitability. The cost of the pads is likely to be higher but they will last a lot longer.
If you have any further questions on brake pads or if there is anything else we can help you with then please call or email us for more information.