You probably right, i only noticed when black bits appeared on sponge and roof while washing x5, if i start fiddling there will be no stopping till i remove all the crumbling parts, will let time & sun do thar for me...no leaks n i won't tamper....thanks for reply

K so you removed the strip and used the black silicon in the channel between the newly exposed edge of the windscreen and the metalwork of roof closest to this edge?

And back to an old post but we had rain out here and it was nothing I have seen for years, it was mud in essence everything was brown as the rain coming down kindly cleared the air of all the dust that was at huge levels....
So took a hose to it and that black trim has gone bye bye....anyhow no leak i am happy...used to frett over knocks scratches and dents but getting too old to worry about these things.....