It's that time of year again as freeze/thaw conditions settle in this week with daytime temperatures hovering around freezing. It's a tricky thing to predict and we tend to err on the side of protecting the trails. Here's a decent article explaining the freeze/thaw issue.
"You're riding along on your favorite trail on a nice winter morning. It's frozen solid and you're having a great ride. After awhile, the sun comes out and a few minutes later the beautiful hardpacked trail has turned to mush, and you and your bike are coated with mud. In this article, originally intended for the GORC newsletter, Sam Mitchell explains how this happens."
Read the rest of the story at Gateway Off-Road Cyclists website.