thx for your reply.
I'm using the latest version of USB-Loader-GX and ... well, I've found the "+" button (Install new game): it ripped from disk to my USB pendrive!
Than WBFS-Manager extracted the file to my PC as a standard ISO file.
To test it I burned a DVD-R using the freeware ImgBurn.
It works fine!
BUT my Wii needed 1,5 hours to rip a 0,33 GB game, that's to say it needs about 4,5 h/GB.
This means 18/20 hours for a lot of games out there (>4 GB).
Any way to extract the ISO file with a PC without a LG disk drive?