Beef ribs expect to take anywhere from 4-6 hours on the smoker. The meat is done when you grab a rib it tears away easily (I wish I could be more specific but well there are to many variables to give an exact time).
Mine seem to take a little less time then porkers. I do not cook to temp I watch for pull back on the bones around 1/4" to 3/8". and the bend when you pick it up from one end should almost break. Good Luck.