Originally Posted by
freeranger
Is the bolt loosening also (you said it's ALL loose again)? If the bolt is loosening, is the bolt threaded all the way to the head of the bolt, or is there a non-threaded portion? If there is a non-threaded portion, maybe it's not threaded far enough up the bolt to allow it to sufficiently tighten. Do you have a collar for the post-if you do, make sure the tabs on the collar aren't touching when tightening. If none of that is the problem, and the post is the correct size, check for any cracks in the seat tube. As JohnD said-hard to tell w/o pics.
It's really as you would suspect for an older bike. Plain ole bolt with threads top to bottom and a regular nut.
But I thought of the solution while reading your reply. Just run to Home Depot, and grab that kind of nut with the plastic in it to keep it from spinning free. I forget what they are called now. Hehe. And probably put the ole one and the new on on there at the same time. The bolt is long enough. That'll probably do it.
I'll try to get pics on here to make the thread much more "moral to the story" for the next readers.