I recently discovered the Sheldon Brown web site. There are lots of information and links that cover everything cycling. The site was last updated about a year ago. Except for the many links, most of the information is timeless. I discovered sheldonbrown.com when I was looking for reliable information about chain wear and chain replacement. It has an excellent technical explanation of chain operation and wear. Sheldon is a well-known bicycle expert and here is an article about him in Wikipedia.