Originally Posted by
Rooney
EDIT: Measured the seat post with a caliper and got anywhere from 26.492 to 26.516. Are seat posts typically smaller than marked? Fully tightened (hanger in-place), the seat post opening measured 26.67 with the calipers.
There you go, the opening is larger than the post, so it will not clamp tightly. I would suggest moving the cable hanger to one side as suggested and see if you get different results.