540i ducts


Cost: $110


Time: 3 hours

BMW 540i duct from Jeff N.'s car.

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.

  • 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.

Click on the image for a larger version.

Cut pattern 2: Thank you Jeff N.  

5b. This is Jeff cut pattern, you have to remove more of the bumper trim. This cut is easier to make.

Click on the image for a larger version.

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.

Click on the image for a larger version.

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.)

> Bracket L: 51 11 8 148 291 - $4.74
> Bracket R: 51 11 8 148 292 - $4.74
> Duct L: 51 11 8 148 055 - $42.60
> Duct R: 51 11 8 148 056 - $42.60
> Channel (intake) L: 51 71 8 148 649 - $9.36 (only needed for track and Autocross use)
> Channel (intake) R: 51 71 8 148 650 - $9.36 (only needed for track and Autocross use)

(Thanks to Jeff N.)


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