I have this problem iI keep running into and itsit's getting pretty expensive. IveI've bought many inner tubes and when iI pump the tire up with air, the inner tube fills up really good except in the area where the valve is. That area is still completely flat and i cantI can't figure out why. I use a prestaPresta valve adapter since iI use a mini hand pump that doesntdoesn't have the prestaPresta pump hole...could that be the problem?