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Discussion Starter · #1 ·
I have had a quick search on the forum and I can't find enough detail.

I have bought the OEM carbon rear diffuser for my 2007 Z4 coupe and I am fitting it myself. Anyone fitted one on here?

I mainly need to know if the rear bumper needs to be removed (I guess it does as I can't see how you would bolt the diffuser on) and if so, how do you remove it?

Thanks in advance.:)
 

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Discussion Starter · #2 · (Edited)
Managed to fit my diffuser now. :D

A few pics that will hopefully give people an idea of what's involved in fitting the diffuser! Pictures don't do it justice to be honest! :thumbup:

First the bumper cover has to come off. 3 plastic rivets in each wheelarch. Just pull the mandrills out of the centre (I used a thin flat blade screw driver to start them off). I didn't jack the car or take the wheels off to do this. Undo all bolts under the car. Then pull the top edges of the sides out as they are just held in by a support bracket. Then just pull the cover backwards releasing where the top of the bumper is trapped by another fixing bracket under the boot (trunk) lid. Easier to do if you have help. Pull back slightly once released as you will have to disconnect the number plate lamps wiring (pull connectors).

Pics of the cover removed:







Pics showing the support brackets for the bumper cover:





Next fix the supplied cutting and drilling template to the edge of the straight style line on the cover. The template is made of paper with an adhesive back. The template is positioned with the centre hole in line with the centre of the numberplate bolts. Take time to get this right as the "wings" on the diffuser follow the numberplate recesses slanting sides, and if not square, will look "odd".



Now the "no turning back, take a deep breath" bit!!! :eek: Drill the 5.5mm holes as per template BEFORE cutting the bumper out. The cover will be more solid!
Cut out the bumper!! Don't bother trying to cut around the template exactly to the curved tabs. Just cut it straight. I used a hand jigsaw I had with a fine blade. Cut easily. :thumbup: NOTE: I did masking tape up the cover above the template just in case the jigsaw marked it. I used a drill to drill the corner radius's on the template before cutting.





Next loosely fit the diffuser to the cover with the centre bolt to check fit and adjust/cut more out if needed. I was amazed at how the diffuser fitted straight off. Even all the holes lined up without having to open out any holes!! Even the bumper sat centre!!
If happy, bolt the diffuser on using the bolts provided as per the instructions sequence. The 4 end bolts can be a bit tricky to get in!

NOTE: Use Loctite on the bolts as they come with plain nuts and washers only. BMW have done this because using lock-nuts on the bolts will chew the carbon when tightened as they are "captive" bolts in the carbon (squared locator under the bolt dome) and using spring washers on carbon can eventually cause cracking!

No photos of it fitted as I forgot to take them!! In too much rush to see it on the car!! :p

Fit the cover back on in reverse of taking off. making sure any panels under the battery box and the heat shield are sat inside the bumper cover!

Stand back and admire!! :thumbup:















 

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Discussion Starter · #9 ·
How much did the difusser cost? Also, did you get it through the BMW dealership?
That's the stinger! The dealer quoted me £340 (UK)!! I got him down to £280 then managed to get a bit more off.

Yes, I just ordered it from my dealer. It's part of the Z4 aerodynamic package. :)
 
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