Probably one of the least understood aspects of road racing is the need to modulate the brake force when approaching a corner. The above figure denotes the force vs time/distance of a "typical" brake application at the end of a straight, approaching a slow corner.
The racing car typically has aero downforce proportional with speed. And, even with cars having low downforce, more force can be applied initially before weight is transferred.
Threshold braking is the maximum braking force that can be applied without locking up the tires.
As the car slows, downforce is reduced and weight is transferred to the front. Braking force must be gradually reduced.
In most instances, a lower brake force can be maintained as steering is added--reducing the brake force as steering is added and more cornering force is applied to the tires. This is called Trail Braking.
Depending on the brake bias settings, trail braking can cause the car to rotate (oversteer), but too much may cause the front tires to be overloaded, causing understeer. Trail braking is used differently on different cars and in different corners, in different ways to control the car on corner entry. (On some really heavy cars, you never trail brake as it overloads the front tires. On these cars you brake in a straight line and "roll thru" the corner much like driving on a short track oval.)
An often forgotten phenomenon is the fact that the car typically will tend to rotate when the brakes are released during trail braking. (It has to do with the fact that upon brake release, the front tires no longer have a braking force competing with the turning force and the front will turn more sharply momentarily.)
The very best drivers will use this phenomenon to apply throttle just as, or slightly before the brakes are released as initial throttle often causes understeer, and the "brake release rotation" oversteer can offset this.
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