I have a suggestion that I have gleaned from a different site. Whether you like it or not, I don't mind either way. Instead of having users post their list of bikes in their signature, have a field in their profile that they can list away.
The reason for this is that if say you were interested in a Trek 5200 and did a search, you wont find 6000 posts from User A who happens to own a Trek 5200 and has it in his/her .signature. It would make searches a little easier to filter through topics. ... and it's not like you want to filter out User A because he/she owns a 5200 and could be useful, but not every singly post from User A.