Today my very last amendments to the bike brought up a pretty bad mood. In the first instance it took ages to get the new Marathon Schwalbe Plus 25mm mounted, it did cost me three tubes already. After they were mounted and I gave them some more pressure the tire slipped out of the rim, I already knew this from another tire before. Dropping pressure and getting things arranged, during riding the tire slipped out of the rim, again. This does not make me happy at all. 

What can I do to solve it. I do not plan to change back to Conti GP 4Seasons …