.m4r is an AAC file with a renamed extension. I use iTunes to convert my AIFF ringtones to an AAC then I go into the finder and change the file extension from .m4a to .m4r (if I remember correctly from when I made my ringtones last fall).
Too bad apple doesn’t let you set your own new SMS tone.
Thanks for your response, I’ve been switching them in itunes but was hoping to be able to create the file in max so that i could just drop it into itunes. Just a little way to save time and some steps. Not a big deal.