Its not very important and most people won't do it but i found that disassembling my centercaps was helpful when painting them. I also looked for ages on how to actually do and couldn't find a helpful DIY. so here goes.
take one centercap
flip it over
remove the circlip
now using either your fingers or a screwdriver, try and push the black plastic cone thing out and push down on the 'hub'. you can in this picture that the black plastic is now above the ridge that is on the hub. it takes a lot of force, patience and swearing to get the first one.
once the first one gets there, the next one is easy. once you get the second on past, slowly lever the hub out. the two ones that have been pushed out are on the right.
and there you go. if you have the need to remove the black thing that holds the hub on then push on the black tabs that stick through the front.
take one centercap
flip it over
remove the circlip
now using either your fingers or a screwdriver, try and push the black plastic cone thing out and push down on the 'hub'. you can in this picture that the black plastic is now above the ridge that is on the hub. it takes a lot of force, patience and swearing to get the first one.
once the first one gets there, the next one is easy. once you get the second on past, slowly lever the hub out. the two ones that have been pushed out are on the right.
and there you go. if you have the need to remove the black thing that holds the hub on then push on the black tabs that stick through the front.