Forward bite is the rear tires' ability to put power down and drive the car off the corner without spinning. It's traction in the direction of travel, as opposed to side bite, which is cornering grip.
You know you’re short on it when the car feels fine until you get to the throttle, then the right rear lights up and you lose ground every lap off the corner. Circle Track Performance names the same tells: “spinning the right rear on exit,” “car feels good until throttle is applied,” “losing ground on long green flag runs.” The levers are mostly at the back of the car — rear tire pressure is one of the quickest, and pinion angle, trailing-arm bushings, and rear spring balance all move it. Driver input counts too: smoother throttle finds bite that a stab throws away. On dirt it’s the currency of the whole night, because a car that turns beautifully and won’t drive off still finishes behind one that does.
Forward bite is where lap time gets made on a slick track — a car that won't drive off gives away positions every single lap.