Just changed the rear tyre - first time I've done that in 40 years!! Just to share some tips really. The bead can be broken with a heavy boot or, as I found, G clamps. These also help to keep the tyre in a position to insert tyre levers before removing the clamps and proceeding. As with refitting, a strong solution of washing up liquid and water around the bead helps removal. After doing all the usual stuff for removal and refitting, I found that the last bit is the worst. Again, I used G clamps to stop the bead popping out when getting the last bit to slot in. When I'm at a point where the tightest bit is, I used my 2 foot lever right in the middle and popped it in. Don't know if anyone else has used G clamps like this but it certainly worked for me. One other thing, when starting to remove the first bit of the bead, I found a piece of wood across the rim is a great way of achieving extra leverage.