01-18-2017, 10:28 AM | #1 |
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DIY Roof rack for M3/M4 with CF roof
Featured on BIMMERPOST.com To install a roof rack on your BMW you basically need 4 attachment points. These attachment points are missing on the M3 F80 and M4 F82 with carbon fiber roof; but all M3/M4 have the necessary thread under the carbon fiber roof - inside the rear side panel - covered by a screw plug (13). Disclaimer: I cannot take responsibility for any damage caused during installation or usage of roof racks. Also please forgive my medium english skills Before we begin: make sure you want to do this! Its a painful moment when you drill a hole in your roof. Step 1. Remove both roof mouldings, they´re just clipped. Step 2. Now you can see the area, where the required mounts should be. Step 3. Take a small drill bit (2 or 3 mm) and drill in the middle of the red marked area. A correct position is very helpful for step 4. In best case you drill the hole exactly centered above the screw plug head. Step 4. Take a lip and spur drill bit to „mill“ a hole in your CF roof. Why a lip and spur drill bit? With the small hole from step 3, you have a perfect centering. Also you can „mill“ the CF without drilling to deep and harm the hidden screw plug connection surface. Step 5. Now you can see the screw plug. Maybe you have to enlarge your drilled whole with a Dremel. You can now simply unscrew and remove the screw plug. Step 6. Fill the hole with a bit of Sikaflex or other, sealing and securing material. Insert BMW star screw with internal thread (part number 07 14 7 153 767) and tighten it. Make sure, the screw lies completely on the side panel - there should be no cf between your screw and panel. Step 7. Seal the star screw with Sikaflex or similar. Et voila - you´re now able to use a roof rack! As you can see in the last pic, i completely removed my roof lining. You don't need to do this - its just hours of work and doesn't help. Last edited by Maltman; 01-19-2017 at 11:59 AM.. |
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01-18-2017, 01:47 PM | #2 |
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THANKS!!!! I nominate this for a feature!
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01-18-2017, 02:31 PM | #3 |
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I wonder why BMW didn't do this from the factory...
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01-18-2017, 10:15 PM | #4 |
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Any risk of cracking the CF when you're drilling?
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01-19-2017, 02:59 AM | #5 |
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01-19-2017, 07:46 AM | #6 |
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01-19-2017, 08:04 AM | #7 |
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Remember - the E92 M3 with CF Roof had these attachment points. I asked some BMW engineers i know personally. None of them told my why BMW made this, but also none of them said its a risk. At the end of the day we won't have a 100% guarantee - but for me i don't see a risk. All forces go directly in the side panel.
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01-19-2017, 10:00 AM | #8 |
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Id rather take my truck to haul something Drilling a hole onto CF roof is just way too painful to tolerate for me lol
But nice write up for those who DDs their M3/M4! |
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01-19-2017, 10:01 AM | #9 |
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They did do it from the factory. As OP has shown, all the hardware is there on the chassis of their vehicles for decades. In the case of the M cars with A CF roofskin ... BMW has to guarantee the integrity of the roof... for whatever the heck an owner does driving it for several years. There's no warranty for the roof once you do this to your car. In truth.. as a manufacturer.. the roof needs to be secure indefinitely, not just 4 years and 50k (or less ). What happens if a 7 year old BMW M car starts getting stains in the alcantara headliner Why take the risk as the manufacturer? It's the same reason that lots of cars are delivered with a big wing that comes in the trunk. Whether or not @Maltman experiences cracks in the CF or leaks will take time to tell but precision counts here. I would think all should be fine. Nice work. |
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01-19-2017, 10:19 AM | #11 |
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Possibly becasuse....
Possibly because the point of a carbon fiber roof is to take weight off of the highest point of the car and not add significant weight above the height of the car.
For those that want the standard rack mount points, they could choose to forgo the carbon fiber roof.
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01-19-2017, 10:41 AM | #13 |
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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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01-19-2017, 10:43 AM | #14 |
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Needs more ///M stripes.
I'm kidding. Nice write up though, well done.
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01-19-2017, 11:41 AM | #16 |
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Be a good place to put grandma (@family vacation)
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01-19-2017, 11:57 AM | #18 | ||
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01-19-2017, 12:07 PM | #19 | |
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P.S. I'd be too concerned drilling into the carbon fiber would compromise the integrity of the roof under extreme stress. I really wish the engineers hadn't omitted this as a roof rack is very useful for skis, and bikes.
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01-19-2017, 01:10 PM | #21 | |
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01-19-2017, 01:40 PM | #22 | |
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