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Old January 20th, 2005, 06:38 PM
Posts: n/a
Problem - Wind Noise With Full Length Flooring on an SD Rack

I have a Safety Devices ‘Highlander high’ rack on my 2002 Discovery. I have a floor for it made out of MDO plywood with a coating of fiberglass resin. I first made and installed a section for the rear ‘upper’ area of the rack. I then made a second section for the front ‘lower’ area (the tapered section in the middle is left open). When I installed the front section the noise from the rack increased substantially. Without the front floor section in place there is a moderate general level of wind noise at 45 mph +, but it is quite tolerable. However with the front floor section in place there is a very loud, low-to-medium pitched howling, most noticeably from the center of the vehicle just slightly back from the windshield. There is an oval cutout 10” back and centered in the floor section to gain access to the tubing for tie downs. As an experiment I taped over this hole but there was basically no change. A guess is that the air coming up over the windshield is being ‘squeezed’ between the roof and flooring (and over the SD rack tubes) causing the howl, as there is no easy exit for it. Final note, there are no lights mounted on the rack at this time to block or disperse the air.

Those of you who have the full floors of aluminum or other material like the plastic RhinoPro flooring have you experienced the same problem? If so, how did you fix it or do you just live with noise? One solution might be an air dam/deflector but I would really not like to do that. I noticed on the Rhino floor website (offroadtuff.com) that they state the floor reduces noise due to better airflow over the roof/rack. This seems to make sense, so I am wondering why is my set up so loud?

Comments, suggestions, real-life-experiences, and solutions are welcome.

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Old January 20th, 2005, 06:48 PM
koby koby is offline
Craig Kobayashi
Join Date: Sep 2003
Location: Orange, CA
Posts: 442
The floorings don't do shit for noise reduction. You need some kind of fairing or obstacle at the front of the rack to defelct wind around the roof rack.

My 4 Hella 4Ks are unbelievably effective at silencing my rack howling.
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Old January 21st, 2005, 12:59 AM
hanchung hanchung is offline
Join Date: Sep 2003
Location: South Pasadena, CA
Posts: 1,182
yup... 4 hella 4000's will do the trick. that's how bad ass the 4000's are
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Old January 26th, 2005, 07:47 AM
Posts: n/a

It is true -- I tried different ideas to reduce the noise on first a custom built rack with a built in floor on my DSII then on my subsequent SD highlander rack.

Nothing came close to reducing the noise level as installing 4 Hella 4ks.

Given the size of the Hellas, I imagine you are going to need a pretty large size fairing up there.
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Old January 26th, 2005, 09:06 AM
Posts: n/a
I have inadvertantly found a partial solution to my problem. This last weekend I decided to try (test) putting lights up. I borrowed a couple (one pair) of Hella 500's from my son with the intent to place them in the center of rack where the major source of noise is coming from. The lights helped, but the most amazing thing was that when I decided to wire them up it was the wire bundle snaking along the roof line (just between the lowerest rack tube and roof) that knocked down the major source of noise ! I first did not tie the wire bundle (wrapped in a plastic wire loom) up tight behind the lower rack bar, in 'drooped' down around the light brackets. It seems that having wire loom 'behind and low' the light brackets on the rack, particularly on the ones in the center breaks up the air and killed the howl. I removed the lights, left the wire loom and the howl remained gone. Bottom line, probably a SD 'bib' would be the best solution as the major source of the noise (the howl) is the air being squeezed between the roof and lower rack bar. Everyone who has posted replies is right that the lights do cut down the general noise a lot so a combo of the lights, 'bib' (or carefully snaked wire loom) seems like the best total solution.

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