Peter Clinch wrote:

Simon Brooke wrote:

It's much more springy than aluminium and IME a bit more springy than
steel.


But simply /along/ a tube (i.e., down a seatpost) the value of "more"
will be somewhere between negligible and bugger all, I'd have thought. I
think you'll need lateral spars somewhere for any degree of appreciable
flex, and a seatpost will be effectively a rigid bar made from any of
the above.

It's not vertical, but about 18 degrees behind that. And moreover, the
bumps (that matter) are coming from the rear wheel, which makes the
effective angle even greater. A long seatpost may flex appreciably.

James