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If you spend a lot of time propelling your manual wheelchair outdoors, you know what a racket low-profile casters make as they shake, rattle, and roll over rough asphalt, weathered sidewalks, and gravel.  Sure, small, hard casters are efficient and maneuverable on smooth surfaces; however, outdoors 4", 5", and 6" hard casters can produce noise and vibration that rings closer to a rumbling skateboard than a coasting wheelchair.  Fortunately, there's a generation of caster technologies that allow quiet, smooth operation in compact sizes - and the name says it all: Soft roll casters.

Solid caster tires can be made of a variety of materials, including rubber and self-skinning foam.  However, most commonly, solid caster tires are made of polyurethane.  Invented in the 1940s, polyurethane is a polymer that can be manufactured into a vast array of resilience, rigidities, and textures (for you, chemistry majors, polyurethane is manufactured by combining a diisocyanate and a diol, two monomers, through a chemical reaction).  As a material, polyurethane variations can be stretched, smashed, or scratched, and remain all but indestructible.  When combining its resilient properties with its utmost durability, polyurethane is clearly a meaningful material for solid caster tires.

With polyurethane being such a versatile material - spanning from liquid to solid forms based on composition - a range of caster tire characteristics are achievable, from hard to soft.  It's within this spectrum where soft roll casters evolved, where a roller-blade wheel is hard, a traditional poly caster tire is firm, and a soft roll caster tire is, well, soft.  In fact, using your thumb, it's tough to depress a roller-blade wheel or traditional poly tire; however, a soft roll caster tire visibly depresses, functioning closer to an elastomer, with great absorption characteristics while not entirely compressing beyond a functional range.  

In everyday terms, a soft roll caster absorbs vibrations and sounds transmitted from rough surfaces, providing a smooth, quiet ride in most circumstances. The ride is closer to a fully inflated pneumatic tire than that of a solid tire, but without the potential of going flat or needing regular maintenance.  And, with soft roll casters available in 4", 5", 6" diameters, and 1", 1.25", and 1.5" widths, they're commonly available for most ultralight applications.

While soft roll casters can prove a benefit to many users, they're not appropriate for all applications.  Because soft roll casters compress more than traditional solid caster tires, they can create more rolling resistance for users who have a lot of weight on the front of their wheelchairs (as with a rearmost rear wheel axle position or forward center of gravity), where soft roll casters can feel spongy to some users.  Also, for sports users, soft roll casters aren't recommended for court use, where roller-blade wheels provide far more responsive, efficient roll rates.  

Soft roll casters, manufactured by a number of companies and available as original equipment or aftermarket, are among the most inexpensive additions that you can add to your chair, with prices ranging from $40 to $65 per pair from online discounters.  What's more, several manufacturers offer soft roll casters in common colors of blue, red, yellow, and purple to color-key to frame finishes, Spinergy wheels, or rear tires.

Cost-effective, colorful, and comfortable, soft roll casters can prove a meaningful addition to many ultralight manual wheelchairs, where they can turn a loud rattle into a quiet roll.

Published 2/06, Copyright 2006, WheelchairJunkie.com