To date most polyurethane tires are used for load-carrying wheels where their advantages are immediately obvious. A more recent development is use of softer polyurethane for cushion tires on indrustial trucks. Polyurethane of approximately 75 to 80 shore A hardness are used for this application and give a degree of cushioning together with increased traction.
In all types of solid tires the constant deflection of the tread cause heat build-up in the mass of rubber materials. The higher the speed of the truck the higher is the frequency of deflection and the higher is the consequent heat build-up in the tires.Tires are normally rated at 10 mph and for higher speeds the loading rate has to be reduced, although by careful consideration of wheel size, tread thickness and tread profile higher speeds can be obtain and polyurethane solid tires are operating in certain application up to 30 mph.
In this instance rubber solid tires would not have been capable of carrying the load and still provide the required manoeuvrability. Steel or hard plastic wheels on the other hand would not have had the required traction and would have damage the pile-cap surface. This is possibly an extream example but it does illustrate how polyurethane can permit completely new design approaches.
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