Sprinkle the rub over the 3 racks of ribs. This can be done 8 hours to 1 day ahead of time.
Preheat grill to low.
Place the ribs on the grill, bone side-down. Add extra rub and squeeze lemon juice over ribs as they cook. Flip them once they're cooked through. The ribs will need to cook for at least 1 1/2-2 hours.