e39 Cardboard In The Sunroof.

[e21Keith]

I know the title of this post sounds odd, but my e39 M5 has a layer of what looks like cardboard glued to the inside of the roof where the sunroof slides back. Over the years this has come loose so scrapes along the glass sunroof as it retracts. Why it's there I don't know, some sort of sound insulation I suppose!

I've seen threads about this on other forums but no conclusion whether to leave it there or pull it out?