Pulley wheel size

[Nelus]

I'm looking to replace my pulley wheels on my shimano rear der. I'm thinking about some light weight ceramic wheels. But as im looking to replace them another question pops up. On friction facts i read that the bigger the size the lower the friction. So if I was to replace them why not get a bigger size? Does anyone have experience with bigger size wheels? What's the max size? And are upper and lower wheel the same size or could you go for a 11/ 13 size, and if so is it better to have a bigger lower or upper wheel ?
Loads of questions. Looking for some help.

[mattyb95]

Would you not struggle to fit the wheels in without removing the little tabs that the chain is supposed to fit through, one on the bottom of the derailleur and the other between the 2 pulleys? With those still in place there would be no room for bigger wheels. Personally don't know if it would even work after that but, see that as your first issue at least.

[Tenlegs]

You can buy them here, http://83.169.41.216/drupalprod/catalog/11
http://www.gs-carbonparts.com/produkte.html
Plenty of info on here too viewtopic.php?f=3&t=36580