Joined: Mar 2007
Posts: 9,163
Likes: 5,346
From: SF Bay Area, East bay
Bikes: Miyata 618 GT, Marinoni, Kestral 200, Soma double cross 2002 Trek 5200, KHS Flite, Koga Miyata, Schwinn Spitfire 5, Mondia Special, Univega Alpina, Miyata team Ti, Santa Cruz Highball, Waterford rs11
Because, when you are knocking 50 on a down hill with no metal but what's between your legs, you want to know your tires aren't going to fail. Just consider it insurance (which most people don't have when riding thier bikes).