This paper describes an analytical vehicle model and a full-vehicle model that consider the effect of suspension geometry on steering pull and drift. Steering pull occurs when a driver applies steering wheel torque to keep a straight-line course, and steering drift means the tendency to deviate from the intended path with a free steering wheel. In designing a chassis system, it is crucial to establish a suspension insensitive to steering pull and drift regardless of manufacturing tolerances. Simulation results show that larger caster trail at the front wheel leads a less-sensitive vehicle towards steering pull and drift, since caster trail reduces the equilibrium slip angle difference between pull and drift by considerably changing the aligning moment diagram. These wheel alignment sensitivities are validated by experimental measurement of drift distance.