Despite the size of the caster (Ø100 - 200mm), R Series is rated as Light duty type - only 60 kgs per caster. Rubber tread is just light cushion but will help reduce noise and surface protection.
Very thick, that is true for both steel bracket and PA wheel. The caster itself is heavy and have strength to support up to few tons per caster. The Swivel head is combined of Flat and Cone Bearing so you will have no trouble operating.