Ok, my point of view about brake ducting is that you need
it for track use only. Then there is the right way to duct
the brakes: sending some fresh outside air directly to the
CENTER (also called hat) of the rotors. And the wrong way:
sending air towards the callipers... pointless.
The only way to have more efficient brakes at the track is
to remove heat from the rotors. (That is why BMW designed
the turbine wheel covers and the angled fins on the M5 3.8l
rotors)
Now that I said that, you might want your car to have an
aggressive look.
Procedure
Hacksaw blades with broken blade handle tool.
Dremel tool and metal rotating bits
Lot of patience and around 3 hours for both sides...
Screwdrivers of all sizes, bolts, washer and nuts from
your favorit hardware store.
1. Place your car on ramps.
2. Remove the cover on the side of the foglight then remove
the foglight.
3. You are going to need to cut the bottom lip of the bumper
cover... If you don't feel comfortable doing it, find a shop
because if you miss...
4. The way I cut the bumper lip was to make a
smaller cut them try the ducts and cut again until the shape
matched perfectly. Takes time, but this is the way to do it
right.
5. You might want to make a paper template to make sure you
get the cut right.
Cut pattern 1:
5a. This is the cut I have made on my car. I wanted to cut
as little bumper lip as I could.
6. You also have to make a notch on the side. This is an
important cut, you don't want this notch too big because you
need a tight fit with the 540i duct.
7. This is the final result. You have to install the metal
bracket and the rear air channel (if you want, this is an
optional part).
8. Install the cover and the foglight back. Depending on the
style of foglight you have, you might have to cut the bottom
of the foglight bracket as BMW came up with a newer style
later.
The whole process takes quite some time, but the result is
worth the trouble.
540i brake ducts from Pacific BMW: ( 800-909-7278 ask
for mail order dept.)