I recently started doing triathlons and am getting killed on the bike - I've been using an old trex hybrid. I want to get a better bike, but am also limited in funds. There's a used miyata seven twelve road bike with shimano 105, cromoly frame for under $200. Any thoughts?

Read the sticky on this exact topic. Not only will it answer your specific question here, but it will give you a much better general sense of how you should go about purchasing a tri bike.