I have a forum and just recently added a website directory ( www.truckmountforums.com/links ) and I have all sorts of websites added. Would this hurt my ranking to have so many sites with a lower ranking than mine?
If you link to a site that has a lower pr than yours you will not be penalized unless that site has been penalized by google.
are they linking back to you? If not then... uh... yes it will hurt you LOL If you are merely asking if linking to lower PR sites will hurt you, if you are giving more PR to them then they are giving to you then yes.