Originally Posted by
Rooney
It's late enough I'm not going to ride again tonight, but tomorrow I'll try tightening with the hanger removed to see what happens. The hanger can't be moved so that may be the problem, but it's original to the bike so I feel like it shouldn't be the cause, right? I'll try a different bolt as well.
I hadn't thought of an adapter sleeve, thanks! I guess it's worth noting, this didn't happen until the seat post changed. Maybe this new one isn't as truly 26.6 as the last (if the last even was — no markings of any kind). I'll also be sure to give everything a good cleaning before doing anything else.
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.
Yes, posts are often slightly undersized. I'll also add that measuring the seat tube ID is not going to get you a specific dimension. There's too much distortion from heat unevenly applied during construction and then the binder slot further changes both the "roundness" and the spread of that upper portion of the ID.
Here's a link to a seat post size thread from a few years ago. I decided to actually measure the various posts I had on hand with a nice micrometer. Scroll down to post 8
Another delay seat post size Andy
Then check oy post 12. This last one is the key IMO. Andy