Place the wood chips in a large bowl. Add water to cover, and let the chips soak for an hour. Drain.
While the chips soak, combine the salt, brown sugar, ancho chile powder, black pepper, garlic granules and cayenne in a small bowl. Pat tri tip dry with paper towels. Rub the spice mixture all over the meat. Let it stand at room temperature for 30 minutes.
Set up the grill for indirect heat. Preheat grill.
For a charcoal grill, arrange the hot coals on one side of the grill. Add the drained wood chips directly onto the coals.
For a gas grill, place the drained wood chips in a smoker box, in a disposable foil pan (poke a few holes in the bottom), or wrap the wood in heavy-duty aluminum foil (also poking a few holes in the foil). Whichever arrangement you use, set the container of wood directly over a heat source while the grill preheats.
Brush the meat with oil. When the wood starts to smoke, place the meat on the heated side of the grill. Cook 5 minutes on each side. Move the meat to the unheated side of the grill. Cover, and cook 25-30 minutes, or until meat is 130°F (or until desired degree of doneness). Remove meat from the grill, and let it stand 10 minutes before slicing it across the grain.