Manual Wheelchairs - World Health Organization

Table 2.7. Aim: to improve manoeuvrability over soft ground
Advantages Disadvantages
By increasing the width, diameter and softness of the castor wheel to increase the contact area,
thus helping to prevent the wheelchair from sinking into soft ground a
n A wide wheel with a raised point on the centre of its
tread can combine low rolling resistance on hard surfaces
with good flotation over soft ground.
n less weight on the front wheels will reduce the rolling
resistance of the front wheels, allowing the wheelchair
to roll more easily.
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n Increasing the contact area of the castor wheel with the
ground can make it more difficult to turn, especially in
tight, slow turns.
By increasing the width, diameter and softness of the rear wheel to increase the contact area,
thus helping to prevent the wheelchair from sinking into soft ground a
n larger-diameter rear wheels can make it easier to roll
over rough terrain.
n In many less-resourced settings, 28-inch bicycle tyres
are widely available; 26-inch tyres are somewhat less
common, and 24-inch tyres are more difficult to find.
n Wider and softer rear wheels can make it more difficult
to turn, especially in tight, slow turns.
n larger-diameter rear wheels make the wheelchair more
difficult to transport.
By moving the front castor wheel(s) forward to reduce the weight on the smaller castor wheel(s)
and make it less likely to sink into soft ground
n More of the user’s weight on the rear wheels will provide
more traction on the rear wheels to drive through soft
ground.
n Overall wheelchair length is longer, making it harder to
manoeuvre in confined spaces.
See also Table 2.4 for related effects.
By moving the rear wheels forward in relation to the user to reduce the weight on the front castor wheel(s)
and make it less likely to sink into soft ground
n More of the user’s weight on the rear wheels will provide
more traction to the rear wheels to drive through soft
ground.
n reduced tendency to turn downhill on side slope, which
requires less energy from the user to correct for downhill
turning.
n User has better access to the hand rim and a longer push
stroke, making it easier to push the wheelchair and
better for the upper extremities.
n easier to perform “wheelies” to negotiate obstacles.
n Wheelchair is easier to manoeuvre in confined spaces.
n reduced rearward stability.
By using rear wheels with knobs, such as those on mountain bike tyres,
to increase traction on soft ground and keep wheels from slipping
n Spikes or knobs on tyres cause additional flexing of the
tyre and thus higher rolling resistance.
n Mud will collect more on tyres with knobs than on
smoother tyres.
a Substituting larger castor and/or rear wheels on a wheelchair not designed to take them can change important functional performance features,
including seat angle, castor barrel angle and seat height (user’s centre of gravity).
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