They'll come around.

About 4-5 months ago I told them (22 at the moment, btw) I was looking at getting my own place (I love my current roommate, we just are going in different directions), selling the car and riding the bike. I went through about 2-3 months about how stupid it was, how I could just live at home (20-25 miles to work, compared to 2-3 from the new place) and so on. Then they went 180 and support me.

I also have considered a motorcycle in the past and got the "over my dead body" speech from my mother the RN. 8 months later I bring it up again, since the new job I have applied for requires some in city travel that may be difficult bike. This time I get the "What about the weather?".

Just give it time...