Roll Couple Distribution is the front-to-rear split of the total roll resistance, normally stated as the percentage of the roll moment reacted by the front suspension. Because a tire’s grip rises less than proportionally with vertical load, the axle that takes the larger share of lateral load transfer loses relatively more grip, so increasing the front percentage adds understeer and increasing the rear percentage adds oversteer. It is adjusted through spring rates, anti-roll bar rates, track width and roll center heights, and it is the primary tool for setting steady-state cornering balance without changing the total stiffness of the car. It is also expressed as a magnitude ratio to the weight distribution, since a car whose roll couple distribution matches its static weight split is a neutral starting point from which to tune.