There have been past forum discussions on repairing OLD Cattrax- the kind with rustable steel tubing for wheels. The tubing corrodes and air won't stay in. These tires have the small central hole, also the rubber valve that takes an inflating needle- valves also shot.
Since the tires are glued to the steel tube--- there is a problem to get inside to put in a large tube.

Comments or references to useful posts welcome.
Newer Cattrax have plastic wheels.