I'm not sure if we are all talking about the same allan screw,for draining and filling. Its the set screw which is very tight to the edge of the tire wheel/rim on the hub as opposed to the sight glass window.Its right beside the rim which makes it very difficult to loosen thats why i'm wondering if removing the tire is necessary. Is there another way that i'm missing. I have a 07 single axle boatmate trailer.I wish i had a pic to explain myself better but camera was lost recently.