Join Date: Jul 2013
Location: Tulsa, Oklahoma
It may sound odd, and I'm not trying to be silly, but are you sure you're sitting squarely on the seat? Surprisingly enough, I have been riding down the road and realize I'm not exactly even on the seat - not like hanging off, but not even either. It might have something to do with the width of the seat vs my butt bones... not sure really. Just know that it happens with me.
How about the gradient of the road (for drainage), is that a possible factor? Does it happen on any road, regardless of where you are?