Originally Posted by
HowellGC
. Unfortunately, I am not sure how to answer the questions precisely. The bolt was tightened to the point that the seat did not move. Hate to think over-tightening was problem -- definitely will consult LBS. .
I think the odds are pretty high that over tightening played a part in this. It's easier to snap small allen bolts than people imagine.
You tighten the bolt too tight, and it's close to failure, then hit a bump which puts a load on the already stressed bolt and it snaps.
I'd second getting a torque wrench.
Also use carbon assembly paste to lower the torque necessary to hold things snug.
Given that this has happened twice, there are really only 2 likely possibilities: defective seatpost, or over tightening. Buy a new seatpost to rule out No 1, and a torque wrench to avoid No 2.