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Wheelchair wheels and tires are one of the most critical aspects of manual wheelchair performance. Yet, this is also an area that is not well understood by many.
For the sake of reducing the breadth of this topic, I am going to focus only on wheelchair wheels with pneumatic tires for active adult manual wheelchairs.
The traditional wheelchair wheel is 24” as measured by the diameter of the outside of the tire. This is also known as 540 which stands for the inner rim bead diameter equaling 540mm. This is a “wheelchair size” not a bicycle size. There is also a 24” wheelchair wheel that is 507mm (inner rim) which is also a bicycle tire size.
This means is that a 24” wheelchair wheel could be 507 or 540, but it is likely to be 540. If it is 540, it is compatible with only wheelchair tires. If it is 507, it is compatible with 24” bicycle tires.
Traditional 24” wheelchair tires are 1”, 1 ¼”, 1 3/8” where the number denotes the width of the tire. Think of 1” as a road tire, 1 3/8” is a hybrid tire, 1 ¼ is something in between. As a general rule of thumb, wheelchair tires are more expensive, lower performance, and more difficult to locate and purchase relative to bicycle tires. They are medical products. Many times, they are grey in color. On the plus side, they generally don’t leave black marks on the floor.
Since 507 wheelchair wheels are compatible with 24” bicycle tires, they are typically used with knobby tires which range in size from 1.75” to 2.25” or even wider since they are intended for (teen) bicycle usage. When you put a knobby 24” tire on a 507 wheelchair rim, the outer diameter of the wheel is close to 25”. Keep this fact in mind.
Modern active wheelchairs now also use a 25” = 559 wheel. The outer wheel diameter is 25” and inner rim bead is 559mm. The 559 size is also a bicycle size. It is compatible with bicycle tires. Since it is compatible with some bicycle tires, there are a variety of tire sizes and treads available. Remember, as you increase the width of the tire, the outer diameter increases. A knobby 559 tire will have an outer diameter of 26”. Therefore, it is known as a 26” tire. A 559 wheel could take either a 25” or 26” tire. It depends.
Assume you have a 25”=559 wheel with a 1” wide street tire, if you put on a wider (knobby) tire with more tread, the outer diameter of your wheel will increase in size (becomes taller). Increasing your rear wheel size means that you will need to adjust your wheel-locks forward. In addition, your axle will now be raised ½” which means that you need to adjust your front caster height to maintain the geometry of your wheelchair. The solution to this problem is to use a second set of 507 wheels with 24” knobby tires. The outer diameter of this 24”=507 wheel is approximately the same size as a 25”=559 with a 1” wide street tire.
Note since knobby tires are wider than street tires, you will need a longer axle with a spacer (I use a 1/2” metal collar) to maintain the distance between the tire tread and your wheelchair. The wheel hub needs to move out (away) so that the tire doesn’t rub against your sideguard (or you). I know this sounds complicated, but it is not.
To summarize, having a 25”x1” =559 primary tire size enables you use a 2nd set of 24”=507 wheels with knobby tires and longer axles. You switch out the wheels as needed. There is no need to modify your wheelchair in any way.
If your primary tire size is 24”=540, then 24”=507 wheels with knobby tires will be larger (taller) in diameter. Therefore, putting on these wheels will raise the rear of your wheelchair. Thus, changing its geometry. You will tilt forward slightly and have more weight on your front casters.
There are also wheelchair wheels that are 26”=590. They are primarily used for sports or wheelchairs for tall people. This size is also compatible with bicycle tires which means a number of tire options are available. A 590 wheelchair with primary 26”x1” street tires can use 559 wheels with knobby (26”) tires since they are approximately the same size.
Another (rough) way to think about it.
Traditional wheelchair wheel size is 24”=540 inner rim (fewer tire options available)
Modern active wheelchair wheel size is 25”=559 inner rim (more tire options available)
Sport wheelchair wheel size is 26”=590 inner rim (more tire options available)
Knobby/wider/bicycle tires are:
24”outer size=507mm inner rim.
26” outer size=559mm inner rim (25”)
26” outer size=590mm inner rim.
Much of the confusion comes from the fact that wheelchair wheels are categorized by inner rim diameter (507,540, 590) or by outer tire size (24”, 25”, 26”). The diameter of the inner rim does not completely determine the outer wheel size since the outer wheel size is also determined by the width/height of the tire too. The inner diameter determines if the tire bead will fit your rim. The outer tire size determines if the wheel with the tire on will fit your wheelchair.
My Analysis of the Problem
If you are happy with your current wheelchair situation then my analysis doesn’t apply to you. But it does apply to the overall problem. The systemic problem is that wheelchair users across the world don’t have the wheelchair wheels and tires that maximize their mobility.
The closest mobility device to a manual wheelchair is the bicycle. The bicycle industry shows us that in order to have the highest functional mobility in various types of terrain, for a wide variety of people, there must be many bicycle wheel sizes and tire options available. The fundamental concept is matching the tire characteristics to the specifics of the terrain and type of use for optimum mobility. This same concept applies to wheelchair mobility.
On the other hand, the Legacy Wheelchair Industry ignores this fundamental concept. They created a standard wheelchair wheel size of 24”=540 (which was purposely not a bicycle size) as the only wheelchair wheel size for adult wheelchairs.
This wheel was provided with minimal tire options. The wheelchair wheel was born with a one-size-fits-all approach that is the opposite of the bicycle industry. Regardless of how short or tall you were, you got a 24” wheel. Irrespective of how or where you would use your wheelchair (urban or rough terrain), your tire tread was the same. Unlike bicyclist enthusiasts, who are seen as widely differing individuals with varying and changing needs and desires, the Legacy Wheelchair Industry took the view that all wheelchair users were relatively the same. The optimization of wheelchair mobility was not considered. The wheelchair wheel just needed to pass a minimum standard.
While this mentality is still the dominant way of thinking, some wheelchair manufacturers have recognized that for the average size adult, a 25” wheel provided more efficient propulsion. Manufacturers of sport wheelchairs realized that 26” was even better for certain sports. Racing wheelchair wheels are even larger.
Now we have the current situation where high cost custom wheelchairs typically use 24”, 25” or 26” by request. Low end wheelchairs still use primarily 24”. So while, 25”=559 or 26”=590 are available, they are still very expensive relative to comparable bicycle wheels.
What is still prevalent in the wheelchair industry is the lack of recognition of the importance of being able to easily switch wheelchair wheels (and wheelchairs) for different terrain and use cases. While the importance of wheelchair mobility has risen over the years, it is still underappreciated. As a result, the typical wheelchair user has a lower level of mobility than they could have – if they had access to proper (affordable) equipment.
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