They're not made to be removed. You can either saw the wheel in half and glue it back together (not as strong) or cut off the hub to get a screwdriver inside to loosen the screw and glue the hub back on. The trick is making a nice cut so you don't mangle the hub.

Or you can do what I did. Forced them apart breaking every single one and had to order all new ones from Mato. All that just to paint the hull bare. Well not completely bare as you cannot remove the suspension without compromising its strength either! The posts for the return rollers as you can see are melted to the hull and they conceal the tops of the shocks.

BUT!! I did see some resourceful individual over at panzerkettan forum put a brass sleeve through it and the hull (on a PZIII) to restore is integrity.