As you know, when you brake to slow the car when approaching a corner, the front of the car dives. Weight has transferred onto the front tires. This dive causes the front springs to compress. When you lift your foot off the brake pedal, the springs expand, popping the front of the car up. Weight is transferring away from the front toward the rear. If you lift your foot off the brake pedal too quickly or abruptly right at the point where you begin to turn the steering into the corner, the front will become unweighted, probably causing it to understeer.
