Caster split is the intentional difference between right-front and left-front caster angles on an oval race car, creating gentle pull toward the inside wall to help the car turn left.
On counter-clockwise dirt and asphalt ovals, teams almost always run more positive caster in the right-front spindle than in the left-front spindle. For example, 2 degrees positive LF and 4.5 degrees positive RF gives 2.5 degrees of caster split. As the wheels steer left into turn one, positive RF caster jacks weight slightly onto the left-rear and lifts the right-front corner while adding favorable negative camber gain, helping the car enter the corner without fighting the steering wheel. Too much caster split pulls hard down the straightaways and can hike the left-front tire or loosen corner entry.
Caster split sets how naturally an oval car turns into the corner and how hard it pulls in the driver's hands down the chutes.