bumpy ride I’d grown accustomed to on my
wooden-wheeled skates, and not even worth com-
paring to the rickety ride of my outdoor skates,
which had metal wheels. Never before had I
realized how important wheels are.
Wheelchair tires and wheels have an even more
dramatic impact on the life of a wheelchair rider.
The smoothness of the ride, maneuverability,
speed and control are all related to the type of
wheels, tires and casters a chair is equipped with,
say therapists, manufacturers and wheelchair
riders who spoke with TeamRehab Report.
Choosing these components is no easy task.
The rehab team must select a combination that
will meet the client’s lifestyle, performance,
maintenance and affordability needs.
This three-part series on tires, wheels and
casters explores what rehab teams should know
about the groundwork of their clients’ wheelchairs.
Tires
There are basically two types of tires used with
wheelchairs:
l pneumatics: which are filled with air and
l airless: which are filled with solid or foam
materials.
Pneumatic tires are lightweight, provide a
smooth ride and have good maneuverability.
Comparative studies show that under most circum-
stances they outperform other tires categorically.
The downside of pneumatics is that they are
the hardest to maintain. These air-filled tires are
vulnerable to punctures and can go flat quickly.
22 TeamRehab Report
Most pneumatic tires consist of the tire shell client but then attach solid tires and heavy wheels.
and an inner-tube insert. The insert is what holds If minimizing the weight of the wheelchair is a
the air. In many cases, when a flat occurs, pat- primary objective, adding heavy tires and wheels
chingthe insert will restore the tire. defeats the purpose. In cases where the wheelchair
“People don’t realize that the rubber used on rider is self-propelling, the rehab team should be
wheelchair tires is very soft: it doesn’t take much especially sensitive to the impact that tire weight
to puncture them," says James J. Kauzlarich, has on the user’s mobility.
Ph.D., an author of several studies conducted on
wheelchair tires at the University of Virginia. Airless Tires
“People go out in the backyard, roll over a rose A study conducted at the University of Virginia
bush and put 10 or 15 holes in the tire," he says. in 1988 identified problems with tires as the se-
“When you get that many holes in it, the inner cond most frequently experienced difficulty
tube usually has to be replaced." He recommends wheelchair riders had with their chairs within a
an airless tire for people who plan to ride in areas year of use. Airless tires are one method of over-
where tires can be easily punctured. coming this problem.
While not every puncture requires aninner- Although airless tires do not have the perfor-
tube replacement, pneumatic tire users should be mance capabilities of pneumatics, they are
warned about the added expense of maintenance superior when it comes to durability and main-
and repairs. Inner tubes can usually be replaced tenance. Since there is no air to worry about, flats
for between $3 and $6. and punctures are of little consequence.
Replacements and repairs made at shops that
specialize in wheelchair parts can sometimes cost
twice what the same items and services cost at
a local bicycle shop. As a consequence, some users If minimizing the weight of the wheelchair
and caregivers go to bike shops for minor repairs.
Others learn to make repairs themselves. Those is a primary objective, adding heavy tires
who can afford one sometimes have a spare tire
available so that their mobility is not inhibited
and wheels defeats the purpose. In cases
during the time it takes to fix a flat. where the wheelchair rider is self-propelling,
Sew-up pneumatics are high-pressure tires that
have an insert sewn into the tire shell. They offer the rehab team should be especially sensitive
exceptional performance but are usually irrepar-
able when punctured. A few tire manufacturers
to the impact that tire weight has on the
have recently introduced “clinchers," which have user 's mobility.
high-pressure pneumatics with removable inserts.
These new models offer the performance benefits
of sew-ups without the risk of losing the entire Terms such as flat-free and no flats are mar-
tire if a puncture occurs. keting terms used by some companies to describe
According to Kauzlarich, to perform properly, their airless tires. There are generally three types
all pneumatics should be maintained within at of airless tires:
least 50 percent of the recommended pressure l semi-pneumatics: made of solid rubber or
level. Tires holding less than that have greater roll- plastic with a ring of air running through the
ing resistance, and the ride is not as smooth. Roll- center,
ing resistance is the amount of friction created l foam: pneumatic tire inserts filled with
when the tire rolls across a surface. The less the polyurethane foam in place of air, and
rolling resistance, the less energy it takes to push l solid: molded out of rubber or plastic.
a tire. For a wheelchair rider, this means proper- Among airless tires, semi-pneumatics come the
ly inflated tires make the chair easier to propel. closest in performance to pneumatics. They of-
The smooth ride of pneumatics is attributable, fer some shock-absorbing characteristics, have
in part, to the shock-absorbing properties of air- good rolling resistance and are lighter than solid
filled tires. Airless tires do not absorb shock to tires. The air trapped in these tires does not need
the same extent. Wheelchair riders who are sen- to be refilled, so the issue of pressure maintenance
sitive to movement beneath them might choose is not a concern.
pneumatics for comfort reasons. Foam-filled tires have better rolling resistance
Because they are generally lighter than other than solid tires, but trail behind the performance
tires, pneumatics add the least amount of weight of pneumatics. Another study conducted by the
to the wheelchair. The less weight involved in pro- University of Virginia in 1988 recorded the roll-
pelling the rider, the easier a wheelchair is to ing resistance of foam tires as between17 and 19
maneuver. percent greater than that of pneumatic tires (for
This factor is sometimes overlooked by rehab loads ranging from 85 to 205 pounds), but 13 per-
teams that order a lightweight wheelchair for a cent less than that of a molded tire.
Nov./Dec. 1991 23
Solid tires are the heaviest and most durable maintenance of tires should be viewed as on par
of all wheelchair tires. Their durability makes with maintaining a part of the wheelchair rider’s
them a popular choice for use in institutional body.
settings. “I’ve heard therapists say, ‘But Johnny needs
A problem shared by all airless tires is that something that is low-maintenance.' Well, I say
there is a greater likelihood for them to be someone’s got to take the responsibility to keep
spherically imperfect. These imperfections can air in and keep the tires clean. If they’re inflated
affect smoothness of ride and other aspects of properly, you only have to do it once a month."
the tire’s responsiveness. However, Ball’s “no compromises” attitude
doesn’t jibe with everyone. “I think you have to
Fitting the Client look at the different needs of the users," says
Determining what type of tire will work best for Simon Margolis, of Rehabilitation Designs in
your client involves asking questions about the Madison, Wis. “The needs of the paraplegic are
very different from those of quadriplegics."
He adds that people who cannot maintain tires
themselves sometimes wind up rolling around on
A problem shared by all airless tires is that flats. This not only has the potential to destroy
there is a greater likelihood for them to be the tire but can damage the wheel and other
aspects of the chair.
spherically imperfect. These imperfections While independence is an issue that should be
factored into your choice of tires, it can be inter-
can affect smoothness of ride and other preted in different ways. For one person, in-
aspects of the tire’s responsiveness. dependence might mean having the ability to
move from classroom to classroom. For another,
it is the ability to get to and from work every day.
rider’s environment and lifestyle, as well as The tires needed to maneuver indoors on an even-
physical abilities. In many cases, it involves ques- ly paved surface are different from those needed
tioning the caregiver as well. to negotiate elevators, city streets, stairs and un-
Jim Fiss is co-owner of Rehab Medical, a St. paved roads. Thin tires with little tread might
Louis company that supplies, orders and fits work fine in the first example, but a wider tire
customized wheelchairs and components. The with deeper tread is better on uneven surfaces.
bulk of his company’s clientele is pediatric. He Tire tread is designed to increase tire traction
says semi-pneumatic tires are more manageable for better stability and maneuverability. There are
than pneumatics for the parents of the children advantages to tires with little or no tread, but
he works with. good traction and maneuverability aren’t among
“For peds [pediatric clients], many of whom them. “With smooth tires you won’t track dirt
are dependent, it is one more thing for the care- in the house, but the traction is awful," Ball says.
givers to worry about," he says about the main- While it might be impractical to have a dif-
tenance of pneumatics. ferent set of tires for each activity, it is necessary
“In our business, we work with a lot of head to consider all of the user’s activities in order to
injury, cerebral palsy and other clients who are choose tires best suited to his lifestyle.
dependent on caregivers. I’d have to guess, but, “There are no cookbook answers," says Fiss.
of the chairs we send out of here, 75 to 80 per- “You have to interview the users. To do a wheel-
cent have ‘flat-free’, or semi-pneumatic tires," he chair right, you have to ask a lot of questions.
told TeamRehab Report, and added that the Knowledge is power, the more you find out, the
disadvantages of airless tires are negligible when better job you’ll do for the user."l
dealing with a person who is dependent on a
caregiver. References: Studies done at the University of Virginia
Rehabilitation Engineering Center include: “Wheel-
Conversely, active wheelchair riders who are chair Mobility: Task 7, Tire Analysis,” by JJ Kauzlarich,
concerned about wheelchair performance and Ph.D., and J.G. Thacker, Ph.D., 1988 and 1989; and
comfort are more likely to want pneumatics. “Task 16, Tire and Wheel Design,” by Kauzlarich and
“For the best performance, you want the high- Thacker, 1983-89. To order these studies contact the
pressure, low-profile pneumatics," says Marty university’s Rehabilitation Engineering Center, PO. Box
3368, University Station, Charlottesville, VA 22903;
Ball of Kuschall of America, a lightweight 804/977-6730: fax 804/977-I258. For a copy of “Wheel-
wheelchair and components manufacturer. Ball chair IV: Batteries, Wheels, Tires, Frames and Drive
is also a wheelchair rider. Trains,” by Thacker, 1989, contact: RESNA Press,
“Solid tires take away from mobility. They add Department 4813, Washington, DC 2006I-4813; 202/
maybe a pound each," he says. Nothing should 857-1199.
The second part of “Groundwork” will focus on
be spared at the expense of the wheelchair rider’s wheelchair wheels and will appear in the January/
mobility and comfort, according to Ball. He says February issue of TeamRehab Report.
24 TeamRehab Report