In the second instalment of this article, we’ll see in some detail about brake bias. F1 brakes are hydraulic brakes. Which is to say they use oil to work. When the driver stamps his brake pedal with some 100 kilos of force, hydraulic pressure makes the carbon fibre brake pads in the calipers grip the carbon fibre brake disc. This makes the disc which will be rotating at about 3000 rpm in a car travelling at 300 kph to slow down. Since the wheel is connected with the brake disc, the wheels slow down consequently slowing the car down. Now, there is some way of adjusting how much hydraulic pressure goes to the front wheels and the rear wheels. This makes it clear that the front and the rear brakes are catered to separately by two hydraulic circuits. This ensures that in the event of failure of one of the circuits, atleast the other circuit will be able to bring the car home safely.
The main purpose of brake bias adjustment is to allow the driver to alter the braking load according to the factors that vary continuously throughout a race. For example, if the front tyres are getting worn, a driver might elect to give more rear-ward braking bias so that the worn front tyres wont have to bear too much braking load. Another situation can be explained. Since the front part of the car is directly exposed to the oncoming stream of air when the car moves, the front brakes will run cooler than the rears. In case if in a race a driver finds that his rear brakes are running a little too hot, he will switch the brake bias so that the front brakes take up more load (load in this context means disc heat) than the hotter rears.
Imagine a slow speed right turn that’s negotiated in, say, 1st gear. The driver is required to brake from, say, 230 kph to 80 kph for this particular corner. At 230 kph just before the braking point, the driver will be in 6th gear, assume. In the space of 50 meters or so, he will have to pop down 5 gears in rapid succession, start braking and at the same time start to yank the steering wheel to the right. At 230 kph there’ll be sufficient aerodynamic downforce to help the driver with his braking. But at 120 kph this will vanish. This leaves only the mechanical grip to help the driver with his braking. Mechanical grip that’s generated by the tyres and the suspension. In this situation, there can be two scenarios for us to analyse the importance of brake bias. The first scenario: the front tyres have either worn too much or they are graining. In either case, the car might understeer beyond control (remember that there’s no downforce at the front to help load the front tyres up). The situation will be further aggravated when the front tyres are giving the braking load too. When done so, the fronts will simply try to lock up and push the car wide. This is clearly not desirable. What the driver can do here is play with the brake bias. Send more braking force to the rears. This will let two things happen. Number one, the fronts will be relieved of some load. Number two, the inside rear tyre will try to lock up and in turn will try to push the back end wide. These two will help the driver to turn into the corner better. The second scenario can be something like this. Imagine the rears being more worn than the fronts. In this case, in all probability when the driver brakes for the corner, the rears will step out of the line sending the car to a half spin. Here the driver uses the brake bias to give more braking pressure to the front which will help relieve the tendency of the rears to lose traction.