Rotor material?

Some rotors are sold for "resin pads only", others do not list
restrictions. What is the difference in materials?

I am using ceramic based pads not normally sold at the LBS, supposedly
similar to what motorcycles have. Because they give me best results.

Other questions while at it:

My rotors are formally 7" and 6". Can I use 180mm and 160mm instead? The
7" one on my MTB actually measures about 185mm. I'd hate to have to
grind down the spacer but might have to because 7" is more rare.

Does anyone know what the raw rotors foer custom-laser deals are called?
Couldn't find any on EBay. Ideally I'd want rotors that are solid like
on motor vehicles, for better heat tolerance. Weight doesn't matter.

--
Regards, Joerg

http://www.analogconsultants.com/