The TT bike is designed to avoid some of the problems potentially caused by adding tri-bars to a road bike (hunched neck and shoulder position, stretched lower back, loss of stability in the aero position, a feeling of being cramped and a reduction in breathing efficiency from the sharper angle between thigh and torso) by having a steeper seat tube angle which opens up the gap between the thigh and torso, with the bottom bracket in effect being further back. The top tube on a TT bike is also shorter, reducing the “stretch” to sit in the aero position. There is also a greater range of positions for the height of the aero bars on the top tube, allowing you to be in a lower more aerodynamic position if desired.

Access to the gear levers is also easier on the TT bike, with gear levels positioned at the end of the aero bars. This easy access promotes staying in the aero position and using the gears efficiently rather than possibly not shifting because you don’t want to keep moving.

Finally there has been some evidence to suggest athletes run quicker off a TT geometry bike compared to a road geometry bike, as slightly different muscles are engaged during cycling.