If you are a cyclist and would like a more comfortable ride, you might want to consider switching to a seat post made from carbon fibre. At a diameter of 27.2 mm, the Easton EC90 is the most compliant seat post that I have used to date. With enough of the post exposed, it offers a much more comfortable ride. If you require a larger diameter seat post, the theoretical advantages of carbon over other materials are much less likely to be realised in practice. At a diameter of 30.9 mm or greater, I’d stick with aluminium. Use a torque wrench and carbon assembly paste.