Size Matters


Choosing the Right Wheel Size

Choosing the right size wheel may not be quite as easy as you would think. This issue of CasterU will fill you in on some of the finer points in selecting the size that will be optimal for your caster application.
There are two key considerations in choosing the right size wheel – diameter and thread width.


The diameter is measured from one side of the wheel to the opposite side with the wheel lying flat, ensuring that measuring device passes over the centre of the wheel.

Generally, the larger the wheel size, the greater the capacity and that’s the major criterion in determining what the diameter of the wheel should be. However, there are a number of other things to consider. Larger diameters will allow wheels to more easily traverse uneven floors, doorways, diamond plate, and dock level thresholds.

Larger diameters will also improve the rollability of a caster, with less push-pull energy required. So, while a 6” wheel may provide the capacity you need, you may want to consider a larger diameter if floor conditions and ergonomics are a factor.

That makes sense but here’s another thing to think about. Increasing the diameter of a wheel decreases its stability. Larger wheels make for taller carts and can change their loading characteristics, because they move the center of mass higher, which makes it easier for loads to tip.

Ultimately making the right choice is finding the perfect balance between capacity, rollability and stability.

Tread Width

To measure the width, stand the wheel upright and measure from the outside of one side to the outside of the other.

As is the case with diameter, increasing tread width will increase the capacity of a wheel.

Increasing tread width is also a way to compensate for challenges with diameter. For example, if the overall height of the wheel is limited by the space in which it is being used, you can increase capacity by increasing the tread width. Also, a way of correcting for the instability resulting from larger diameters (mentioned above) is for the wheel to have greater surface contact. That can be done by increasing tread width.

Another major consideration in determining the optimal tread width is load distribution or capacity per square inch. There are some applications where that measurement is very important. For example, the membrane of the cargo hold in an airplane has a critical capacity/square inch threshold. Exceeding that threshold may cause the shell to rupture. You can increase the load distribution (and reduce the capacity/area) by increasing the tread width of a wheel. You can also use double the number of wheels, providing twice as much load distribution.

Manoeuvrability is also a factor. Wheel sizes with narrower tread widths have less surface touching the ground and will therefore be easier to turn.

So, there you have it – a simple guide to specifying the right wheel by finding the perfect balance between diameter and tread width. Because, ultimately size does matter.

If you need help determining the right size wheel for your application, contact your Algood Sales Rep or reach out to our customer service team by email or by phone at +1 (800) 254-6633.

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1 (800) 254-6633

Algood Casters has manufactured, designed and developed industrial and specialty casters, brakes and wheels since 1969, in capacities from 25 to 65,000 lbs.