Abstract: A bicycle seat tube clamp may include a clamp body having an opening for a bicycle seat tube. The clamp body may have a separation defining first and second opposing clamp ends which may have respective first and second aligned fastener shaft-receiving passageways therein. The first clamp end may have a cylindrically shaped nut-receiving passageway intersecting the first fastener shaft-receiving passageway. The second clamp end may have an enlarged fastener head-receiving passageway aligned with the second fastener shaft-receiving passageway. The clamp may also include a fastener having an enlarged head with a convex lower surface. A cylindrically shaped nut may be positioned in the nut-receiving passageway and engage the fastener shaft. A shaped washer may surround the shaft and have a concave upper surface engaging the convex lower surface of the fastener head. Alternatively, the concave surface may be integrally formed in the enlarged fastener head-receiving passageway.