Crumbling rear brake lamp
The bootlid-mounted brake light on my 2008 BMW 1-Series coupé (123d) has started to fall to bits. I have a new one, but it seems you have to attack the boot lid with a grinder to get it to fit. It appears you have to remove a tag from the top of the cut-out and also cut a small notch at the bottom.
There is a trade service bulletin from BMW, but obviously the dealer will not provide details. There is information on a US website, but it just gives details of what the bulletin covers, not the actual job. Martin Marsland Having purchased a genuine BMW unit, you would expect it to either fit without modification or to have been given the full details of any modification needed included with the lamp. This seems not to be the case and, as you say, there are quite a few references to this problem on American and European websites.
It seems there are two choices: either file off the small metal tab in the recess of the boot lid or cut the new lamp carefully to allow it to pass the tab. The BMW method is to file off the tab and then repaint the exposed metal to prevent rust from forming. There is a very good description of the job with pictures at this BMW 1 forum: http://bit.ly/1ooh0um