Everything you ever wanted to know about electric motors for RC plus a lot of things you didn't even know you wanted to know can be found in Big Jim's RC Motor Black Book
. Scroll down the page in this link and you will find a link for more info on this info packed volume. Sadly, big Jim keeled over from heart failure not long ago, but his legacy lives on in this book. Every fast electric guy I know got that way after reading this book.