Every 3-6k or when it needs it. At every oil change I measure my tread depths across the surface (inside/middle/outside) and judge when I need a rotate or tire pressure change from that. I also run my hand along the edges to see if there is any feathering. So far I have gotten about 20-25k out of 1-2/32 on the Michelins I have
Two Three Zero
FRPP, "Stealth" CAI, Debadged, wider tires, louder stereo, turbo mainfold in the wrong place...