Originally Posted by Pleiades

The rear wheel is difficult because (unlike the front) it bizarrely has a tubeless tyre type cross-section; there is a small bead hump on the inner edge of the bead seat. To get the tyre off easily the bead needs lifting over this hump into the dropwell in the centre of the rim. Simply pushing and using brute force, just causes the bead to drag across or snag on the hump. The easiest way I�ve found is to use a small 9� tyre lever with a thinnish spoon end which you can get under the tyre�s bead and then lift (and push/lever) over that troublesome bead hump.