I found a nice video and an article on tire thread wear, when to replace, what to look for. After all, tires and brakes are most important parts as far as safety is concerned.
Video,
http://www.youtube.com/watch?v=H3Yq7DMRwbw
Article,
http://www.rattlebars.com/tirewear/index.html
Video,
http://www.youtube.com/watch?v=H3Yq7DMRwbw
Article,
http://www.rattlebars.com/tirewear/index.html