Wheelchair Tire Numbers Explained

Wheelchair tire numbers can look confusing at first, especially when the same tire may have both an inch size and a metric size printed on the sidewall.

Learning how to read these numbers can make it much easier to identify the tire you have and compare it with a replacement. The most important thing is to match the tire to the correct wheel or rim rather than relying only on the general wheel size.

What You’ll Learn in This Guide

Where to find the tire size on your wheelchair tire
What inch sizes such as 24" x 1" or 24" x 1-3/8" mean
How to read metric tire numbers such as 25-540 and 37-540
What the first and second numbers in a metric tire size represent
How common metric sizes compare with inch-size labels
Why two tires labeled 24 inches may not fit the same wheel
What to check before ordering a replacement wheelchair tire

Where Do I Find My Tire Size?

Start by looking at the sidewall of your existing wheelchair tire.

Most tires have the size molded, printed, or stamped somewhere along the side of the tire. You may see an inch size, a metric size, or both.

For example, a tire may be marked:

24" x 1-3/8" 37-540

These two markings describe the same tire using different sizing systems.

Helpful Tip

If your tire still has readable numbers on the sidewall, take a clear photo before removing it. That information can be very helpful when comparing replacement tires.

Understanding Inch Tire Sizes

Wheelchair tires are often described using inch measurements such as:

24" x 1"
24" x 1-3/8"
24" x 2"

The first number generally refers to the approximate outside diameter of the tire, while the second number refers to the approximate tire width.

For example:

24" x 1"
Approximately a 24-inch tire with a 1-inch width.

24" x 1-3/8"
Approximately a 24-inch tire with a 1-3/8-inch width.

24" x 2"
Approximately a 24-inch tire with a 2-inch width.

These inch sizes are useful for describing the general tire size, but they should not be the only measurement used to determine fit.

Understanding Metric Tire Sizes

Many wheelchair tires also use a metric size written as two numbers separated by a dash.

Examples include:

25-540
37-540
50-540

This sizing system gives more specific information about the tire and the rim it is designed to fit.

Example: 37-540

37
The approximate tire width in millimeters.

540
The bead seat diameter of the rim in millimeters. This is the important fitment number that tells you which rim diameter the tire is designed to mount on.

So a 25-540 tire, a 37-540 tire, and a 50-540 tire all share the same 540 mm rim diameter, but they have different tire widths.

Quick Wheelchair Tire Size Conversion Guide

Wheelchair tires may be labeled with an inch size, a metric size, or both. The examples below show some common equivalent markings you may see when identifying wheelchair tires.

25-540 = 24" x 1"

37-540 = 24" x 1-3/8"

50-540 = 24" x 2"

25-559 = 25" x 1"

50-559 = 25" x 2"

25-590 = 26" x 1"

Important

Use this chart as a quick reference rather than a substitute for checking the complete tire size. Inch-size labels can vary between tire styles and manufacturers, so always match the metric rim-diameter number before ordering a replacement.

Why the Second Number Matters So Much

The second number in the metric size identifies the diameter of the rim where the tire bead sits.

This number needs to match the rim. A tire designed for a 540 mm rim cannot automatically be used on a different rim diameter just because both tires are described as 24-inch tires.

24 Inches Does Not Always Mean the Same Rim Size

The inch measurement is a general tire-size description. Different tires may use the same inch label while being designed for different rim diameters. Always compare the full tire size, especially the metric rim-diameter number, before ordering.

Real Wheelchair Tire Examples

Here are a few common examples of how the inch and metric numbers may appear together:

24" x 1" (25-540)
A narrower tire designed for a compatible 540 mm rim.

24" x 1-3/8" (37-540)
A wider tire that also fits a compatible 540 mm rim.

24" x 2" (50-540)
A much wider tire designed for a compatible 540 mm rim.

These examples show why the complete tire size matters instead of simply looking for a tire marked 24 inches.

What About Tire Width?

The first number in the metric size gives the approximate width of the tire.

For example:

25-540: approximately 25 mm wide
37-540: approximately 37 mm wide
50-540: approximately 50 mm wide

A wider tire may require more clearance around the wheelchair frame, wheel locks, side guards, and other nearby components.

Even when two tires use the same rim diameter, that does not automatically mean every width will work correctly on every wheelchair setup.

Do Not Rely Only on the Wheelchair Model

The same wheelchair model may have been sold with different wheel and tire configurations.

Replacement wheels may also have been installed at some point during the life of the chair.

Because of this, the size printed on the existing tire is often a better starting point than assuming a tire size based only on the wheelchair manufacturer or model.

Before Ordering a Replacement Tire

Before choosing a replacement wheelchair tire, check:

The complete size printed on the existing tire
The inch size
The metric tire size
The rim diameter number
The tire width
Whether the tire is pneumatic, solid, or another type
Whether the wheelchair has enough clearance for the tire width
Whether an inner tube is required

Quick Tire Size Checklist

Find the size printed on the tire sidewall
Write down both the inch and metric sizes if both are shown
Match the rim-diameter number exactly
Check the tire width
Confirm the tire type
Compare the replacement specifications before ordering

Ready to Find Your Tire?

Once you know the complete tire size, compare the inch size, metric size, width, rim diameter, and tire type with the replacement tire specifications before ordering.

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