There is a huge bolt right in the centre approx, 24mm... No i'm not kidding.... Get that off ( you'll need a long wrench ) and the whole drum parts from the hub and bearings. You'll need a large flat edge screwdriver or chisel and a hammer to knock the outter edge back out so you can remove it. Don't stress too much though, When refitting don't forget to knock the edge of the bolt back in to stop it loosening. Hope that helps.
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