Of course, with the rise of aero road frames, many seatposts supplied with wind-cheating bikes have gone the way of their TT cousins and are now full aero.
In one sense, this is completely understandable as a bike is an aerodynamic system, not just a selection of profiled parts, and in a world of marginal gains every little counts. And it can seem even more important if, like me, you’re striving to make the most of all twelve watts your legs can put out.
On the other hand, it can be a right pain in the neck when it comes to replacing a damaged post and makes upgrades basically impossible. The thing is, every aero frame uses that particular manufacturer’s own aero seatpost, so it’s not a case of grabbing the post from a Specialized Venge and jamming it onto Felt’s AR2 should something go wrong. In certain cases, there may be the potential for using a standard cylindrical 27.2mm post with some kind of shim, but it’s far from a recommended way of doing things and certainly not a long-term solution.
There’s also the option of buying an aero post that will fit on your standard road bike. These have a normal round tube at the bottom which flairs out into an aero design once the post has left the seattube.
The main issue with these is that they look ridiculous, especially if you need more post than there is aero section so you end up with a hybrid aero post/round post look. There’s also a limit, frankly, to the amount of aerodynamic benefit you’re likely gain with an aero seatpost on a standard bike. You’re likely to gain far more by embarking on an stretching and flexibility regime that’ll allow you to hold a more aero body position while generating the same, or similar, power.