Depends on how you intend to use them... I've had aero bars on a regular roadie before, too. If you want to maximize the aero benefit for Tri/TTs, then you'll need to rotate your upper body position lower/flatter by moving the seat forward (which usually also means adjusting the height/tilt to compensate). But, I've seen aero bar set-ups on long-distance tours as well, maybe partially for efficiency but more to relieve some of the pressure on the hands and resulting shoulder/neck strain by allowing you to put the weight on your elbows/forearms part of the time. In that case, you don't necessarily want to change your pedaling position, but you'd likely need to raise/shorten the stem to decrease the reach to the elbow/forearm pads.