A propulsion system for a manual wheelchair, the system comprising: • a mounting clamp configured to attach to the manual wheelchair; • a propulsion unit selectively attachable to the mounting clamp, the propulsion unit comprising: • a drive wheel assembly, wherein the drive wheel assembly is supported on a carriage; and • a support suspension, wherein the support suspension is configured to provide linear movement of a drive wheel of the drive wheel assembly relative to the manual wheelchair, characterized by • an actuator, which provides selective linear movement of the carriage between a drive position where the drive wheel contacts a support surface and a stowed position where the drive wheel is out of contact with the support surface, wherein o the support suspension comprises rolling and/or sliding means conducive to supporting linear motion, with the support suspension comprising a linear bearing and slide member assembly having at least one linear bearing and a slide member (22, 24) for accommodating the linear movement of the drive wheel assembly, o the support suspension comprises a resilient suspension member providing a tractive effort force to the drive wheel, o the carriage is attached to one of the at least one linear bearing or the slide member and has a suspension reaction mount in contact with the resilient suspension member, and the mounting clamp is connected to the other of the linear bearing or the slide member (22, 24), o the actuator is an electrically driven actuator attached at a first end to a mounting block, with the mounting block being attached to the at least one linear bearing and the carriage is attached to the slide member, the mounting block being selectively attachable to the mounting clamp and has a spring seat, and the resilient suspension member being positioned between the spring seat and the suspension reaction mount, and o the actuator has a second end that selectively engages the suspension reaction mount to move the drive wheel out of contact with the support surface. • a mounting clamp configured to attach to the manual wheelchair; • a propulsion unit selectively attachable to the mounting clamp, the propulsion unit comprising: • a drive wheel assembly, wherein the drive wheel assembly is supported on a carriage; and • a support suspension, wherein the support suspension is configured to provide linear movement of a drive wheel of the drive wheel assembly relative to the manual wheelchair, characterized by • an actuator, which provides selective linear movement of the carriage between a drive position where the drive wheel contacts a support surface and a stowed position where the drive wheel is out of contact with the support surface, wherein o the support suspension comprises rolling and/or sliding means conducive to supporting linear motion, with the support suspension comprising a linear bearing and slide member assembly having at least one linear bearing and a slide member (22, 24) for accommodating the linear movement of the drive wheel assembly, o the support suspension comprises a resilient suspension member providing a tractive effort force to the drive wheel, o the carriage is attached to one of the at least one linear bearing or the slide member and has a suspension reaction mount in contact with the resilient suspension member, and the mounting clamp is connected to the other of the linear bearing or the slide member (22, 24), o the actuator is an electrically driven actuator attached at a first end to a mounting block, with the mounting block being attached to the at least one linear bearing and the carriage is attached to the slide member, the mounting block being selectively attachable to the mounting clamp and has a spring seat, and the resilient suspension member being positioned between the spring seat and the suspension reaction mount, and o the actuator has a second end that selectively engages the suspension reaction mount to move the drive wheel out of contact with the support surface. o the support suspension comprises rolling and/or sliding means conducive to supporting linear motion, with the support suspension comprising a linear bearing and slide member assembly having at least one linear bearing and a slide member (22, 24) for accommodating the linear movement of the drive wheel assembly, o the support suspension comprises a resilient suspension member providing a tractive effort force to the drive wheel, o the carriage is attached to one of the at least one linear bearing or the slide member and has a suspension reaction mount in contact with the resilient suspension member, and the mounting clamp is connected to the other of the linear bearing or the slide member (22, 24), o the actuator is an electrically driven actuator attached at a first end to a mounting block, with the mounting block being attached to the at least one linear bearing and the carriage is attached to the slide member, the mounting block being selectively attachable to the mounting clamp and has a spring seat, and the resilient suspension member being positioned between the spring seat and the suspension reaction mount, and o the actuator has a second end that selectively engages the suspension reaction mount to move the drive wheel out of contact with the support surface.