Wheelchair occupants often remain in their wheelchairs for surface transport. Research has focused on frontal impact, with less emphasis on rear impact. Due to variation in wheelchairs, the use of a standardised wheelchair model may not represent occupant loading in rear impact. Wheelchairs are often adapted to better suit the needs of the occupant and commonly added postural supports were created in a computational model of the BioRID dummy seated in a wheelchair subjected to the IIWPG 16km/h, 10g rear impact pulse. Stiffer supports were found to reduce occupant spinal loading as compliant surfaces bottom-out, causing contact with the stiff underlying structures.