This can be really easy or very hard depending on the last time it was done and the orientation of the planets.
Removing the 3 Giant Flat Head Screws
In the old days I used to turn them out with a pin punch and a hammer -- this is not the way to do it and destroys the screw.
Buy an impact screwdriver at an autoparts store. (If unfamiliar, this is a terrific little device with a screw driver end that when hit with a hammer transforms the linear blow into a revolutionary movement.) This thing saves the day and only costs about $15. Make sure to verify that you are loosening and not tightening before using it -- it is more difficult to check this than you think and the results can be disastrous. Also buy extra bit ends -- they tend to break if your get a particularly suborn screw and if they are the cheap ones.
Removing A Stuck Drum
After the 3 screws are out the drums can sometimes be very hard to get off. If it won't move at all, its likely rusted on. Try the following steps until successful.
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- First check that the drum spins -- sometimes poorly adjusted breaks can hold it on. You might also try backing off the adjusters all the way; sometimes a groove can be worn or built up in the drum and though loose, the drum won't slide off.
- Get out the PB Blaster, the Liquid Wrench, or the WD40 and spray down the studs, 3 screw holes, and the other holes. Your goal is to try to get some penetrating liquid between the drum and the hub and as little as possible into breaking surface and pads.
- Find the drum bolt pulling holes -- these are the "other" holes on the face that don't hold the flat head screws. After-market break drums can have more or less of these. Find a bolt that threads nicely and crank it in. The bolt will push the break drum off. Be sure not to go too far and get the drum stuck in a cock-eyed position. The threads are the same as the Flat head screws but find a bolt since it is hard to put the torque on the flat heads.
- If all else fails, get a lead or soft headed hammer and EVENLY tap the drum off. Be sure not to hit the drum too hard or the backing plate -- breaking things is easy with a hammer.
To prevent this from happening again, use anti-seize all over the place. This will prevent the thing from rusting on in the first place.