Approximate installation time: 1.5 hours.
Tools needed: Drill, 6-8mm drill bit, 10mm wrenches + Allen wrench.
Installation difficulty: Easy (basic mechanical knowledge)
As you'll see, the installation is quite simple, but it does require some patience and checking that everything is in its correct place to ensure it's properly centered. Don't rush and make sure you follow the steps. A correct installation always guarantees a better finish.
Screws or "hardware" (in parentheses for diffusers that include the differential add-on)
x5 - 18mm spacers.
x2 - 10mm spacers.
- Nuts - M6.
- Washers - M6 wide neck.
- Allen - M6x12mm.
- Allen - M6x20mm.
x2 - Allen - M6x25mm (use with 10mm spacers)
x5 - Hexagonal - M6x35mm (use with 18mm spacers)
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The following image shows different markings to identify the position of the main plate and the use of the spacers. It is important to note that each screw will have two washers, one towards the screw head and the other towards the nut, to provide a larger clamping surface.
(NOTE: The image shown is the main panel of the E36 V1 model. The position of the bushings and screws indicated is the same in the E46 model.)
For reasons of space and to facilitate the work, it is recommended to first fix the main plate to the spare wheel and mark the holes that would go to the lip with the M6x35 Hex screws, fix the removed lip (if the bumper model allows it, otherwise, it is recommended to remove the bumper) and then return the assembly to the car.
Red square: 18mm spacers + M6x35mm hex. (Lip M or OEM bumper).
(Yellow square: Only refers to diffusers for e36)
Squares in green: 10mm spacers + M6x25mm Allen screws. Main fixing to the spare wheel well.
Lines in blue: Use M6x12 Allen screws to fix the "fins" to the main plate, as well as to join the pieces together.
For the ends, it is recommended to drill 3mm pilot holes and use self-tapping screws to correctly position this part. Once aligned, use M6x20mm Allen screws here. (Depending on the version, this part may have 2 or 4 holes per piece).
(NOTE: The image shows the E36 model for clarity. The same procedure applies to other models, including the E46.)
You'll see that the center plate has holes at the ends with variable widths. This will allow you to adjust the ends regardless of your bumper model. It will also allow you to adjust the intermediate pieces to align with the exhaust tip, both in angle and reach.