Logic seldom works against emotion.

Taking time off to clear one's head, get centered, sow oats, etc., between phases of life is a time honored tradition.

http://en.wikipedia.org/wiki/Gap_year

I would get your mom talking about the phases of her life and what she wished she had done if she had the opportunity when she was younger. Tell her that your ambition is to volunteer for a year of clearing minefields in Zaire just as soon as the ebola epidemic eases up. If your delivery and timing is good she will be begging you to ride your bike instead.

Just kidding about the Africa part. Seriously, you're SOL until you turn 18. After that you're going to have to redefine your relationship with your mom. Good luck with that.