This study focused on whether wheelchair users showed enhanced ability to estimate the space required for locomotion with familiar and unfamiliar wheelchairs. Tetraplegic participants, who lacked somatosensory input from the upper limbs and were unable to obtain information about the dimensions of a wheelchair from their hands, and able-bodied control participants made judgments of whether a doorway was passable with their usual form of locomotion (use of a familiar wheelchair or walking) or a new form of locomotion (use of an unfamiliar wheelchair for both groups). The relative perceptual boundary was determined, which was the ratio of the perceptual boundary between passable and impassable widths to the minimum passable widths. Tetraplegic participants accurately determined passable doorways in both familiar and unfamiliar wheelchairs. The control participants showed less accuracy for the wheelchair condition than for the walking condition. The findings obtained from the tetraplegic participants suggest that adaptation to altered body dimensions occurs in a short time only under a well-learned, familiar form of locomotion. The findings also suggest that individuals are likely to rely more on visual memory of a passable space than somatosensory information about the dimensions of the wheelchair when determining passable doorways during locomotion.