brake bias

[lotus72]

hi, first time in your forum, why would a driver need to adjust his brake bias during a race? is it to do with fuel load and tyre degradation?
thanks for your help

[enzo]

Two factors primarily - changes in the grip level of the track, and therefor the weight balance of the car under braking, and changes in fuel load, which again changes the weight balance under braking.

[PhilThomas]

So how would that work? Say you start with a relativly full fuel tank, would the bias be 60-40 f:r (just a basic example here...)? How would the bias change throughout the race? In other words, how would the bias start, and how would it be changed through the race (move the bias to the rear a little more??)??

[Tony_Simpson]

if we take the example of touring cars (BTC, Aussie V8) then they are front engined with the fuel tank in the rear. On full tanks the weight is more balanced front to rear (as an example), so under cornering, braking etc a certain amount of weight transfer takes place. As the fuel comes off less weight is at the rear, so less weight transfer takes place. To make the most use of the tyres, mainly the fronts, the brake balance is moved forward as more weight is took off the car, as less weight transfer means the loads on the front tyres change. This means you can brake later etc.

The effect of having too much balance to the front still means you lock the fronts first and understeer off, and too much balance to the rear means the rear of the car is trying to over take the front, like an oversteer effect. If it is a wet surface then more rear brake is applied to stop the fronts locking in the slippier conditions.

Hope that helps a bit.