murray 40" riding lawn mower-wheels

all right. got the correct drive belt and installed it. now had to replace all four tires--got three done but can't get left side rear wheel off. bathed it in pb blaster and beat on the back side of the rim. Nothing happened. the retaining clip is off and the key is pushed all the way in just like the other back tire but can't seem to get the wheel off. This is the only thing keeping me from testing everything else out. Help please

These can be impossible to remove without destroying what you're trying to fix. If heat doesn't do it, you may end up with a cut-off wheel on a Dremel tool. Good luck!