Depends on what tire you're running. With motorcycles max lean angle is decided as much with the tires on your bike as with your skill and ability to be smooth as it is with the bike itself.

When hard parts start to touch you're leaning too far and most "modern" sportbikes will catch a footpeg or something else hanging low before the tires will let go with a competent rider aboard. (thats why they put the "hero sliders" on the bottom of the foot pegs, to let you know you're too far over BEFORE you go so far that you lose it because the foot peg will move, but the next part you touch wont and you will go down)

I used to drag hard parts on my 82 CB900 all the time and pulled the rear end off the ground and lowsided before I reached the end of the tires grip. (I was keeping up with a 600rr and should have known to back off a bit but was too busy patting myself on the back for keeping up with that old of a bike)