The USDA advises that ribs are ‘done’ once the internal temperature of the thickest part reaches 145°F. However, as Meathead advises there is a difference between ribs (or any meat for that matter) being ‘done’ and ‘ready’.
It is true that ribs are safe to eat once the internal temperature reaches 145°F, but for best results waiting until your ribs are at an internal temperature of 190 – 203°F degrees.
Because all ribs are slightly different thickness and size its hard to give an exact timing for cooking ribs, so its always best to have a trustworthy digital meat thermometer for best results.
For a rough guide, this recipe the ribs took around 7 hours to reach an internal temperature of 195°F.