if you have a combi parts catalog it has a specific section for wheels
on a C4000 cube it is in section 14.
it shows 2 types of wheels and tires, one for solid press on tires and hub and also for a split rim and tire.
There is a tire and wheel assy part number
a tire part number
and a rim part number
Look in your catalog again

or call combi and give them your machine model and serial number info and they will look it up for you ;o)