How to mount wire bead tyres without damaging them? I have a Schwalbe Marathon Plus 700x25 tyre which is very difficult to mount on my rim. The rubber has almost no flexibility. The wire make the tyre directly goes either outside the rim, or inside the edges of the walls of the rim. I can mount it though, but with damages to the edges of the tyre:

and with one or two broken levers:

How to mount these tyres without damaging the beads of the tyre and without too much strength?
The classical trick is to move the beads of the tyre into the well of the rim  down to the center of the valley, so that the apparent tyre diameter become larger than the rim diameter. Then the tyre can be pressed with both hands towards the point where the lever can be finally used to insert the bead into the rim.
However, this is almost impossible with Marathon Plus tyres, which have a very strong wire and a inflexible rubber: when one spot is moved into the well of the bead, others go off, so that the diameter is never increased sufficiently.
To solve this issue, I tied several knots around the tyre with strings, so that the tyre is pressed into the rim.

However, with a classical knot, it would not be possible to press the rubber sufficiently so that the tyre would fit into the well of the rim, because these Marathon tyres have very little flexibility. To I used a Tarbuck knot, which makes it easy to get the sufficient pressure. One knot every 3 or 4 spokes allows to get a constant pressure.

It is then quite easy to push both sides of the tyre towards the point where the remaining work can be done with the levers, but without excess force.