In our focus on manual wheelchairs, we have looked at the effects of horizontal and vertical rear wheel position in manual wheelchairs. This month, let’s look at lateral position and camber in the rear wheels of custom folding and rigid frame wheelchairs.
Lateral position refers to the position of the rear wheels relative to the frame of the wheelchair. Imagine that the rear wheels are perpendicular to the ground and parallel to each other. Adjusting the lateral, or side-to-side, position of the rear wheels allows the wheels to be sleeved in closer or further away from the frame of the wheelchair. This decreases or increases the width of the wheelchair, respectively, which will have an effect on the lateral stability of the wheelchair. Lateral stability is important in preventing tippiness when a person leans to the side beyond the base of support. In addition, the lateral position of the rear wheels affects the position of the upper extremities relative to the pushrim of the rear wheels.
Camber is different than lateral position and refers to the slant, or angle, of the rear wheels. The pictures below give a visual representation of 0° of camber (as shown in the photo to the left) and 8° of camber (as shown in the photo to the right).
Photos are copyright of Sunrise Medical, Inc.
Depending upon the model of wheelchair used, there are several choices of camber available, such as 0°, 3°, 6° and more. There are several benefits to having some camber on the rear wheels of a custom folding or rigid frame wheelchair. (Camber is not available on standard wheelchairs.) Camber helps to improve access to the rear wheels by bringing the top of the pushrim closer to the person in the wheelchair, facilitating an efficient push stroke1. Camber provides lateral stability to the wheelchair, making the wheelchair more difficult to tip sideways. Camber also promotes improved maneuverability when turning. When travelling along a side slope, such as what occurs when a sidewalk follows the grade of a driveway, camber helps to decrease the tendency of the wheelchair to turn in the downward direction of the slope. Depending upon the degree of camber in the rear wheels, camber may also help to protect the hands from being bumped by, or scraped from, nearby objects2. This occurs because the overall width at the top of the pushrims is narrower than the overall width at the base of the wheels, providing additional clearance for the hands. Since the overall width of the wheelchair is increased at the base with the introduction of camber, access to narrow spaces within the environment may be compromised.
As we can see, a person’s access to the rear wheels is affected by both the lateral position and the camber on the rear wheels. How the rear wheels are positioned laterally and how much camber is selected will be dependent upon a person’s needs for wheel access, maneuverability, lateral stability and the environment in which the person will be using the wheelchair.
- Rehabilitation Engineering & Assistive Technology Society of North America. (2012). RESNA Position on the Application of Ultralight Manual Wheelchairs. Downloaded from http://resna.org/resources/position-papers/UltraLightweightManualWheelchairs.pdf
- Tsai, C.Y., Lin, C.J, Huang, Y.C., Lin, P.C., & Su, F.C. (2012). The effects of rear-wheel camber on the kinematics of upper extremity during wheelchair propulsion. BioMedical Engineering OnLine, 11, 87.