The invention relates to a wheelchair (10), comprising a frame (12), a tiltable seat (70) operatively connected to said frame (12), said seat (70) having a back member (72) connected to a bottom member (82), and a curvilinear support member (110) connected to said seat bottom member (82) and operatively and movably engaging in said frame (12). A gear rack (40) is connected to said frame (12), said gear rack (40) operatively connected to said seat (70) for controlling the tilting of said seat (70), whereby said curvilinear support member (110) has a center region spaced apart from and located above said frame (12) about which said seat (70) tilts.
