if they haven`t been off for a while there may be a wear ridge on the drum which hooks round the shoes preventing removal,there is no easy way passed this but to get in with a couple of levers and keep working at it,when you get them off,grind off the lip and you wont have the same problem again,also give the drum a rub down with emery where it locates onto the outer rim of the hub
cdc
November 2010