A wheelchair frame includes left and right first frame members, each having a first leg for supporting a seat. The first legs are arranged on opposite sides of a central axis of the wheelchair. At least one cross-brace is connected, by the ends, to the first legs of the left and right frame members. The cross-brace has a non-circular cross-section along a section between the ends. The wheelchair frame includes left and right second frame members that are pivotally connected to the left and right first frame members. The second frame members are foldable and may be fixed in a position in that is generally parallel to the first legs of the left and right first frame members. A cross-brace is connected, by the ends, to the left and right second frame members. The cross-brace has a non-circular cross-section along a section between the ends.