What is weight transfer? A car at rest distributes its weight over the four tires. When you accelerate, the front gets lighter – an extreme example is a drag car doing a wheelie. The result is weight transfer off the front tires, and onto the back tires.
When you step on the brakes, weight transfers from the back to the front.
When you turn, weight transfers from the tires on the inside of the turn to the tires on the outside of the turn.
That’s all simple enough, but gets a little more complicated in fast driving, because you are often performing a combination of these things simultaneously. Sometimes — actually quite often — you are still doing some braking while turning at the entry of a turn, and a key to going faster is beginning your acceleration before completing the turn.
The amount of traction you have at each tire is dependent on how hard the tire is being pressed against the pavement. Since any kind of weight transfer causes a change to this pressure, then the traction you have at each tire is constantly changing with weight transfer.
If weight transfer did not occur, traction would always be consistent, and the car would be easy to drive quickly. Since weight transfer is unavoidable, the next best thing is to cause the weight to transfer as predictably as possible. This is done by driving smoothly. When you apply the brakes, don’t slam them on, progressively squeeze them on. Squeeze into and out of the throttle. Turn the steering wheel gently, and try to make only one turn of the wheel to achieve the arc you want through the corner. As you accelerate out of the corner, unwind the wheel as you squeeze on the throttle.
The above does not mean that you do not use the brakes, the gas, or the cornering ability of the car to their limits. It means you transition between them gently, with touch, and in a way that minimizes how they upset the car. In order to go really fast, it is essential to first become smooth and consistent in your handling of the car.