AERO- DUCT by Strong-Strut

BMW parts manual refers to them as "aero duct" so we're told they have something to do with the air flow or air currents near the wheels. Many other models of BMW's also have aero ducts including the ///M5. BMW said they divert the air flow in front of the rear tires and help prevent hydroplaning in the wet. Also has something to do with noise reduction but in a convertible, its noisy anyway !

We have heard three explanations and have no idea whether any one is correct. One explanation is that they change the air flow near the tires which results in a quieter drive with the top down. The second explanation is that it somehow sets up favorable air currents for cooling the rear brakes. The third is that it has a favorable affect on the air currents that improve air flow to the rear of the car and keep water away from the rear tires.

One thing we do know for sure is that the plastic factory parts last about 6 months and then they require replacement. The Phoenix/Scottsdale, AZ BMW dealers price these at $17 each plus local tax.

The Strong-Strut version of the aero-duct is fabricated from aluminum alloy and the parts are riveted together for a lifetime of service. The production version pictured here, is machine made and hand assembled. It is powder coated with a durable, baked on, textured black finish.

Pictured below is the plastic OEM aero duct after 8 months of service. The plastic is split, cracked and deformed and is beat to death from road debris impacting it. Replacing these every year at approximately $35 per set may not be the best thing to do. The Strong-Strut aluminum version is $85.00 including domestic postage. Our Aero Ducts will last the lifetime of your car with reasonable care. See pictures of production version further down the page.

Below.....factory plastic units, badly deteriorated

Below.....Alloy Aero-Duct by Strong-Strut

scroll down for more pictures