if they haven`t been off for a while then you sometimes get a ridge on the inner face of the drum which `hooks` itself round the shoe and makes it very difficult to get off.You can grind this off and clean up the hub and drum and apply copaslip to make removal easier in future.One thing I remember doing is to remove the plastic bung on the backplate at the adjuster,knock a wheel stud into the drum assy and this leaves an access hole to pull the adjuster pawl off of the ratchet with a piece of welding wire and wind the adjuster off from the rear and this gives the clearance to remove the drum,it may need some sharp raps with a 2lb hammer to shock it free.The wheel stud just gets knocked back into the hub with a punch.Good luck.
cdc, May 2012