The difference may be a lot, or it may be nothing. The main purpose of a TT or Tri bike is to put the rider in a position to generate the maximum ratio of power/aerodynamic drag (while at the same time remaining within the rules of the sport). For some riders, that might mean there is no difference between the two types of bikes. For other riders, the Tri bike may place the rider in a very different position. In either case, it is generally more about the position of the rider, than any fundamental mechanical difference between the bikes.trekman10 said:I know this has probably already been covered but I looked in the past forums and could not find it. What is the diference between a TT bike and a Tri bike. They look the same in pictures.