Cast iron or semi-steel wheels combine strength and durability with economy. They have very low rolling resistance and can withstand abusive conditions and high loads. Trew semi-steel wheels are “Made in the USA” from Class 30 cast iron with 30,000 psi tensile strength. A small amount of scrap steel found in all cast iron is the origin of the name - semi-steel wheels.
For exceedingly abusive and heavy-duty applications, forged steel is the choice. The forging itself is nearly indestructible in any caster application and, consequently, bearings are always the limiting factor in capacity. Forged steel wheels, because of their durability, will often be the best value in the long run.