That's it. Same as in road cycling, the biggest air resistance is not due to the bike frame but due to the rider that will have to sit on it. The larger cross s

That's it. Same as in road cycling, the biggest air resistance is not due to the bike frame but due to the rider that will have to sit on it. The larger cross section is hard to ignore. To improve speed, make the bike more comfortable so muscles can be more relaxed. To improve speed further, reduce cross section while maintaining a comfortable ride. For the last few percent, get a suit that sits tight. All the rest is for those that want to save five seconds over an ironman ride, where group riding is not allowed. But hey, tri bikes do look cool, have fun.