Yes, I know, this is a terrible idea, and I am planning on replacing the seatpost eventually, but mechanically, I'm pretty sure I'm right about this.
I got this fine SR Sakae 26.6mm aluminum seatpost off a used hardtail mountain bike. I noticed it had a hairline crack at the top of it, and so I immediately replaced it with a 26.8mm seatpost -- the size that probably *should* have been in there to begin with. Here's what the crack looks like:
Fast-forward a few months, and I find myself in need of replacing a 26.6mm captain's seatpost on my tandem. (That's a whole other saga.) Well, so now I find myself in possession of this perfectly sized seatpost with a crack at the top.
Thing is, this is the captain's seat on a tandem, and the crack lives PRECISELY underneath where the stoker stem clamps on, like this:
Now, I intend to keep an eye on the crack and see if it grows, and plan to replace the seatpost for good measure anyway, but I think that the physics of this clamp should completely negate the weakness posed by the crack. Aren't I right, or am I smoking crack?