I recently got a second hand bike and on paper everything looks fine. It is a frame size S which says fits 160-175cm. I'm around the 169-170 range so I am right in the middle of the range so it should be no issue.

However, when trying to fit the bike, I have lowered the seat post as low as it gets, but for some reason I'm still finding it hard to pedal comfortably.

I have to mention I'm having butt sores although maybe that is normal if I haven't ridden a bike in a while. So I guess my question is are the butt sores due to the seat post height or might there be another factor? I have this feeling that I might have a smaller leg length than normal but they look normal to me.