My wife definitely knows how to change a tire and has done it, but if the tires haven't been taken off by me since the last trip to the tire shop she wouldn't be able to loosen the lug nuts. I taught her how not long after getting married. My dad taught me at about 10 years old how to change a bike tire and I've never had one changed by someone else since. I agree with the above sentiment. To paraphrase a parable, "Change a man's tire and you help him for a day. Teach him how to fix it and you help for a lifetime."