A center-of-gravity tilt-in-space wheelchair (10) includes a base (12), a seat assembly (14) for supporting an occupant, and tracks (46) supporting the seat assembly (14) for selective seat movement relative to the base (12). Wheels (16, 18) are adapted to support the base (12) relative to a supporting surface. The tracks (46) serve as rolling or sliding surfaces that allow the seat assembly (14) to rotate with respect to the base (12). Each track (46) has a constant-radius arc (A) with a focal point (P) that is adapted to be coincident with the center of gravity (CG) of the wheelchair occupant. A low-friction support (50) supports the base (12) relative to the seat assembly (14). The low-friction support (50) may include low friction elements that mate with the tracks (46) to support for the tracks (46). The support (50) can be adjustable to permit the overall tilt angle range of the tracks (46) to be adjusted. The wheelchair seat assembly (14) can be adjusted to maintain the focal point (P) of the constant-radius arc (A) of the tracks (46) coincident with the center of gravity of the wheelchair occupant. The front and rear wheels (16, 18) can be adjusted fore and aft relative to the focal point (P). A coupling (74) includes plates having upper ends operatively attached to one another with seat canes (62) therebetween and lower ends releasably attached relative to the side tubes (44). The lower ends can be movable in a longitudinal direction relative to the side tubes (44) while remaining operatively connected to the side tubes (44). A base frame can include side tubes (40) having an offset (182) at a front end and a caster housing (52) supported by the offset (182). The offset (182) is directed up to minimize the height of the side tubes (40) and down to maximize the height.