Wrapping meat when smoking it is known as a "Texas crutch". It's usually done around 160°F, when the fat begins to render and evaporate which causes the meat temperature to rise much slower. This phase of cooking is known as the "stall". Wrapping the meat helps to prevent the evaporation and helps power through the stall phase in a shorter amount of time. I do reccomend wrapping chuck roast in foil or butcher's paper to cut down on the cooking time, and then removing it when the meat reaches around 185°F. This way you get the benefit of a shorter cooking time, but still get a good crisp bark on the exterior.