This article describes the problems of wheelchair tires, the problems encountered with specific types of tires, some of the newest features of specific types and what to do when living with extraordinary problems. Further, the advantages and disadvantages of specific types of tires are examined along with their purposes. Finally, recommendations are made based upon expectations and conditions of daily usage
Wheel Casters
A. Problem Specifics
Wheel Casters
Getting you from point-A to point-B in a wheelchair is more than just a wheel-issue. The wheels chosen determine how and where you use the chair. Wheelchairs, normally, have two sets of wheels - two large ones in the back and two smaller ones in the front but some chairs for specialized usages (sports, power, etc.) may have as many as three sets of wheels. The wheels consist of various components: tires, rims, push-rims, solid wheels, wheels with spokes, "quick-release" axles and front-wheel casters, to name a few.
The tire is the only part of the wheel that makes ground contact. Some manual chairs have several sets of tires for seasonal or climate changes. The rear wheels are the largest on manual wheelchairs that aid in "self-propelling", known as "drive-wheels" because of the "push-rims" attached to the rims of the tires. Chairs designed for a caregiver or attendant to push may have larger tires in the front since there is no need for "drive-wheels", per se. It is advisable to save the wheelchair's serial number and "tire-details" in case of replacement along with the seat-width, depth, frame-color and other pertinent factory information that may be needed at a later time during the life of the wheelchair.
B. Symptoms and Causes
Tires, with or without inner-tubes, have been known to go "flat". There are two classes of tires - pneumatic (air, inner-tubes) and puncture-proof (solid and "flat-free"). How you use and where you ride will help to decide which type is best for you. High-pressure tires (air) are narrower than the everyday pneumatic tire. The tread pattern is minimal - not as deep as a pneumatic tire while requiring a greater inflation pressure. Many manufacturers recommend tires that are designed with increased camber (angling with the vertical) and tread to be "off-center" to maintain good surface contact. The tire is of a smooth, light-tread for indoors and thin for mobility. For out-doors and better traction, the tire is wider with a medium, knobby tread.
Pneumatic Tires
They are made of rubber and require an inner-tube, under pressure. Pneumatic tires are widely used on most manual and power wheelchairs because they are generally lighter, shock-absorbing and offer good traction on most terrains. While pneumatic tires are the most popular, they require the highest degree of maintenance. This is because the inserts consist of a thin liner that can be easily punctured by thorns, nails or other sharp objects penetrating through the tire.
With these tires, you must always be prepared for a flat, especially if you spend a lot of time outdoors. In addition, you must keep a close eye on maintaining the appropriate pressure since leaks from pneumatic tires are common and should be replaced every couple of months.
Puncture-Proof ("Flat-Free") Tires
These are made of rubber or plastic (usually polyurethane). The rubber puncture-proof tires are similar to the pneumatics but the inner-tube consists of a solid material such as foam, plastic or rubber. These tires are essentially "flat-free" and require less maintenance than the pneumatics.
However, a single, solid insert is generally heavier by an average of 1.5 times than that of a single pneumatic insert.
The combined difference in weight between having two pneumatic inserts and two solid inserts is approximately two to four pounds, depending on the material. While this does not sound like much, the additional weight can have a significant impact when it comes to transporting and/or propelling the wheelchair. They are also stiffer, not as shock-absorbing and tend not to grip the surface, as well. These features may adversely affect the performance of your chair if you spend a lot of time outdoors in slippery conditions, if you often travel up-and-down hills or if you ride often on rough and/or rocky surfaces.
Replacing a solid insert can be very difficult to do on your own and should be taken to an expert, authorized service center. Unfortunately, servicing a wheel can be expensive. Changing a tire with a solid-insert takes a little longer than a pneumatic-insert (inner-tubes) so you can expect the cost for the service to be a little higher. Bicycle shops can also provide repair or installation services for most wheelchair tires and are, generally, more inexpensive.
Puncture-proof tires are made of "solid" plastic (no inserts). They are, generally, the least expensive but are, at the same time, low performance, greatly reducing your comfort and are damaged somewhat more easily. Solid plastic tires are commonly found on hospital chairs that are designed for indoor use, only. New technologies have enabled puncture-proof tires to become more lightweight and comfortable user while still providing longer wear. Typically, these tires are constructed of a semi-pneumatic "foam" and rubber combination which are available in various tread-designs and sizes.
Pneumatic tires and tubes are the most inexpensive combination to buy. For a standard, rear tire for manual wheelchairs, prices depend on materials used. They are made of a lower grade rubber with simple wire reinforcing beads that hold the tire inside the rim edges. The more expensive tires are made of high-quality rubber with reinforcing of Kevlar on the side-walls. Generally, foam, puncture-proof inserts are more expensive than those of a hard, plastic-type material.
Tires are available in many different tread designs and widths, accommodating almost any type of terrain. Treads range from very smooth to extremely knobby such as those typically seen on high performance mountain bikes. The smoother the tread and the thinner the tire, the less rolling resistance required to push the wheelchair. If a majority of time is spent indoors, a smooth to lightly treaded, thin tire is desirable. If a lot of time is spent outdoors, a wider tire with a medium "knobby"-tread has better traction on rough surfaces. Special tread designs and widths are available for traversing over snow, dirt, turf and grass.
Power wheelchair users tend to use medium treads and thicker tires on all wheels to accommodate many different surfaces with smooth treads not being a problem with a power-chair. Many manual chairs are not equipped to support different wheel sizes. The most appropriate diameter is determined by how long your arms are and how high or low you sit in the chair. You should be able to easily reach the entire, upper half of the push-rim without bending forward, "hunching" your shoulders and not flexing your elbow out too far.
C. What To Do About Persistent "Flats"
Persistent flats are a problem, to say the least. The user is left with two choices - continue pur-chasing the inexpensive tires whenever they are flat and beyond safe repair or invest in a tire that is guaranteed and warranted to never go "flat" based upon its construction components.
For example, Flat-Free Tires (Canada), Inc. is an importer and distributor of a tire ("Amerityre") which uses closed cell polyurethane foam that is considered "airless" for bicycles, wheelchairs, lawn and garden products, commercial and residing lawnmowers and golf-carts. These tires are 100% recyclable and meet or exceed the performance of conventional rubber tires for a slight increase in cost per tire.
D. Cautions and Comparisons
Pneumatic (Air) Tires
This type of tire is light-weight, more shock-absorbing and has good traction on most terrains. The high-pressure versions are, normally, lighter than the standard pneumatics, are narrower (smaller-footprint) and have shallower treads for decreased rolling-resistance (easier to push and rolls further per push). Many users prefer the softer ride of a conventional pneumatic for the improved push-ability of the high-pressure tire which are, also, favored by athletes for perform-ance reasons which have a "protection-belt" made of natural rubber and are skid-free.
Conversely, inner-tubes have a thin liner that can be easily punctured by sharp objects and should be replaced every 3-4 months depending on usage to reduce the potential for flats due to wear with outer tires every 6-9 months when the tread may appear worn or cracked. The small volume of air at higher pressure does not afford as much shock absorption making it a harder ride than a conventional pneumatic tire. The smaller "footprint" of the high-pressure tire may result in diminished traction on wet or slippery surfaces, tend to wear out quicker than a conventional pneumatic when used for street use and may require a valve converter for inflation.
Solid, "Flat-Free", Puncture-Proof Tires
This type of tire is essentially flat-free and requires less maintenance since the same pair of solid inserts can be used over and over again. On the other hand, they are heavier, less shock-absorb-ing and replacement can be costly and difficult.
Wheelchair "Flat" Tires
Wheel Casters
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