I had two racks of baby back ribs. I rubbed them down the night before and let them rest in the fridge for 12 hours. I smoked them at 210 deg for 4 hours. I then wrapped in foil with apple juice for an hour then unwrapped and sauced them up. Back in the smoker for a half hour. The internal temp was 183 deg when I took them out. The taste was out of this world. The part I need to work on is getting it more tender. They weren't dry but they took some work to pull the meat off the bone. What did I do wrong?
You may not have done anything wrong, sometimes the pig is just tough. It is difficult to get an accurate IT reading on ribs because the meat is so thin and the bone throws the reading off. Most people go by the look of the meat pulling off the bone or they insert a thin skewer into the meat between the bone and if it goes in easy it is done. Others with more experience will pitch in with their methods and you should go with what works best for you.
This will help you out with your next cook for ribs.
http://www.amazingribs.com/tips_and_technique/are_they_ready.html
To make them more tender you might try a variation of the first two steps. You did 4 hours smoke and 1 hour foil with apple juice, a total of 5 hours. Maybe try 2.5 hours smoke and 2.5 hours in the foil next time, followed by the same 1/2 hour at the end. If that still doesn't make them as tender as you'd like try 2 hours smoke and 3 hours foil. Make sure you seal the foil tightly (roll the edges instead of folding) so no steam escapes.
I also like mine fall-off-the-bone tender. ;)