In its simplest form: your ribs are done when you can pick up a rack of ribs by one end and the rack bends easily, like a cooked noodle, and the meat in the middle begins to tear a little bit.
If there’s a tear, they are done. If you prefer them to be “fall off the bone,” they’ll need to go until the bend test turns into the break test!
Mitch Tip: This is very important, your rack should be bone side up when doing the bend test!
It seems an internal temperature between 195 and 205 is when the most flexible “bend” occurs in the ribs; this is due to the breakdown of the collagens and rendering of the fat within the rack.
Where to grab your ribs: go about five or six bones in; about a third of the way, to do a proper bend test.