tube change question

[OakLeaf]

Also, coat the tube with cornstarch before you install it. That will help keep the tube from sticking to the tire over time, and it'll also help get the valve stem straight in the rim. I like to keep my spare tube in a ziploc bag with a tablespoon or so of cornstarch.

(PS - People change tubes both ways. Personally I prefer to take the tire all the way off. It might possibly depend on the tire and rim, which way is easier.)