In many dynamic applications, polyurethanes are superior elastomeric materials because they can be formulated to high hardness; thus they will deform less under a given load than will conventional soft rubbers. Polyurethanes in the 90A-50D Shore hardness range have especially good load-bearing properties. But even at comparable hardness, all polyurethanes are not equally useful for dynamic applications. Extensive laboratory testing has shown that parts made from Airthane polyurethane prepolymers will provide excellent dynamic response.

To establish a starting point on designing a load-heavy polyurethane wheel or roller, it is suggested that you determine the percent deflection. Deflection for a specific wheel, tire, caster or roller under a known load can be calculated using the following equation.