Wheel with a semi-permanently enclosed annular material

A wheel assembly comprising:

• (a) a toroidal wheel component having a Shore hardness between about 70 A and about 95 A formed of a single integral piece having a lateral outer surface and a medial outer surface, which is adapted during use to define a hollow toroidal core, said toroidal wheel component adapted to have, during use, an outer circumference for rolling on a surface, and an inner circumference adapted to contact a wheel hub, and said hollow toroidal core having an outer circumference radially displace from the outer circumference of said component and adapted to have, during use, an inner circumference radially displaced from the inner circumference of said component, wherein said component is discontinuous between said component inner circumference and said toroidal core inner circumference and has a toroidal lateral inner edge displaced from the lateral outer surface and a toroidal medial inner edge displaced from the medial outer surface;
• and
• (b) a toroidal spacer lying between and in continuous abutment with said edges;
• and
• (c) a replaceable toroidal component comprising a stiffness-modulating material inserted into said toroidal hollow core in use;
• and
• (d) wherein said replaceable toroidal component is selected from a group of components having varying stiffness modulating properties in order to change the resiliency of the wheel assembly.