Wheelchair Rear Wheels
The rear wheels of a wheelchair are available in several sizes and types and choosing the right wheels can make the difference between a functional wheelchair and a non-functional wheelchair.
Rear wheels, when self propulsion is a goal, will normally be either 20", 22", 24" or 26" in diameter. The larger the wheel the easier it is to push the chair however, the larger the wheel the higher the seat height which can be a problem for some users. The smaller wheels, while being harder to propel, do make seat height more functional and foot propelling possible. When self propulsion is not an issue some chair models offer 12", 16" or 18" air filled rear wheels but these are usually tilting frame wheelchairs.
Most of the larger sized wheels (20" - 26") are available with either air or solid tires. When a user is primarily indoors, solid tires have advantages over air tires in that they are easier to propel and have virtually no maintenance issues. Air tires produce a softer ride and have better traction which is beneficial for users who are regularly outside on sidewalks, roads and grass. The traction aspect of air tires applies only to those self propelling. A caregiver pushing a wheelchair will not notice the traction aspect of air tires but will notice the difficulty of pushing a chair with under inflated air tires. They downside of air tires is they require regular maintenance to maintain tire air pressure, wear out faster and are subject to flats.
When a flat occurs in an air tire, the easiest solution is to replace the tube within the tire. As long as a tube of the correct size can be found, they can be purchased at any bicycle shop and anyone who can fix a bicycle flat should find it easier to fix most wheelchair flats. While bicycle tubes are usable in wheelchair tires, bicycle tires are not the best choice for replacement wheelchair tires. Wheelchair tires are designed not to mark floors where bicycle tires aren't. Therefore, in a pinch a bicycle tire will work but the user may be in danger from whomever cleans their floors.
Wheelchair Solid Inserts
Air tires can be purchased with products called solid inserts which prevent the occurrence of flats but when the tread wears off the tires it is virtually impossible to replace the tire without destroying the insert. Most dealers are not equipped to replace or install solid inserts so usually end up purchasing new complete units from the manufacturer or reverting to solid or tubed tires.
Wheelchair Rims
The rear wheels can be either spoked (bicycle type), or mag (plastic like composite wheels) rims. Spoked rims will not accept most solid tires but mags will usually accept both air and solid tires. Spoked wheels are a stronger wheel and will not flex when pushed, thus saving energy for the user. The downside of spoked wheels is that there is a bit of maintenance required in keeping the spokes tight. Mag rims are maintenance free but will flex a bit when pushed. In the event of breakage, spoked wheels can usually be repaired where mag wheels must be replaced for a fairly hefty price.
Wheelchair Push Rims
Another option to consider about rear wheels is the push rims which can be either, chrome, aluminum, composite, plastic coated or projection. Chrome, aluminum and composite push rims are most common. All are fairly light and, depending on the manufacturer, included as no charge options when purchasing a wheelchair.
Plastic Coated Wheelchair Push Rims
Plastic coated push rims are designed for people who have difficulty gripping standard push rims. There are two drawbacks to plastic coated push rims. The first is that eventually the plastic will begin to chip off making the surface of the push rim hard on the hands. The second problem is that when traveling down a ramp most users will allow the push rim to slide through their hands applying pressure on the push rims to control speed. There is so much friction created by plastic coated hand rims that using this method of speed control will burn the palms of the user's hands. Plastic coated push rims are best suited for those who rarely, if ever, self propel in areas of uneven terrain.
Projection Wheelchair Push Rims
Projection push rims have approximately 8 projections extending vertically or at a bit of an angle off vertical about 3" long from the push rim. People who do not have the ability to grip the push rim at all can use this type of rim to self propel. Using the hand rims to control the chair speed is impossible and would likely lead to broken fingers.
