... what is the idea behind the larger rear tire? I hadn't wanted a bike until I saw a used tw200 on craigslist. The look of the bike really stirred something up. I don't care to go to fast, so the top end isn't an issue. Now that I've got the bug I'm just wondering if this awesome bike is right for me. So yeah... what is the deal with the rear tire? I mean, I'm going to get one anyway, but still...