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Originally Posted by Serious
I do aerospace composites for a living. With this kind of structure and how its bonded to the chassis you wouldn't see any performance decrease drilling a few holes, like a previous poster said the e92 m3 has these holes in the roof from the factory.
In all likelihood BMW eliminated the holes in the CFRP roof as a cost savings measure. Drilling holes in carbon panels can be a source of defects, scrapped parts, tooling cost, added machining time etc. Keep in mind they're making a lot more of these now then they did back in 2005/6 timeframe (development of e92).
Be careful drilling at home though, drilling carbon fiber is not the same as metals. The feeds/speeds required are much higher to reduce fiber breakout (drill bit snagging fibers). I would suggest drilling a pilot hole initially and progressively opening it up to size. Only use new drill bits. You also want to seal the holes after drilling, you don't moisture getting in there and compromising the matrix (resin). I would also make sure there isn't a possibility of allowing moisture ingression into the roof & cabin area.
That said I would probably feel comfortable doing this to my car if I owned the CF roof. Stupid BMW forces you to get the moonroof to have roof rack mounts.
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I agree 100%. I guess BMW just saved some costs, they thought "its an M4, its not supposed to be used for ski holiday" - and thats the sad point. I used my E92M3 for ski holiday and i want to do the same with my M4.
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I would suggest drilling a pilot hole initially and progressively opening it up to size.
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Thats exactly what i suggest. Drill with 2mm a pilot hole, then with the help of a 15mm wood drill bit you can easily "carve" an exact hole to remove the screw plug.
