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If you’ve ever driven with a roof rack installed, you might know about the annoying wind noise it can create.
Many cyclists like carrying their bikes on a car roof because it keeps the trunk or tailgate clear. It’s the crossbars that create roof rack noise, so how do you fix this?
In this article, you’ll find tips on how to stop the noise and make your drive more peaceful.
Why Are Roof Racks Noisy?
It is the crossbars of a roof rack that are often noisy as we drive along. This type of noise is known as “Aeolian sound” (aka Aeolian tones). It occurs when wind passes over or through objects.
The noise is created by oscillating vortices (whirling sections of air) behind the crossbars. These have a strong periodic property that creates a constant tone. As with some elements of cycling, this phenomenon is a matter of aerodynamics.
How much noise a roof rack makes depends partly on its shape and the smoothness of airflow over that shape. For instance, a square-shaped crossbar is likely to create a lot of noise from the many vortices that form behind it into a “Kármán vortex street”.
A cylindrical crossbar should be less noisy than a square-shaped one, but an aerodynamic shape like that of an aerofoil is quietest of all.
Another cause of wind noise in roof racks is loose, missing or damaged rubber seals, strips and end caps. Anything that hinders smooth airflow can create this problem. Damage to a car’s trim does a similar thing
How To Reduce Roof Rack Noise
There are various ways to cut out roof rack noise or prevent it with your buying decisions. We’ll go over some of the main ways below.
1. Buy Aerodynamic Crossbars
This preemptive solution won’t help you much if you’re already experiencing noise from your roof rack. But, you need to pay attention to the crossbar shape to prevent it.
A product like the Thule AeroBlade Edge Roof Bar for flush roof rails is deliberately designed to cut out wind noise. This one has WindDiffuser technology to reduce noise and aerodynamic drag.
Edge bars like the one exampled above are more aerodynamically efficient (thus quieter) than load bars. With the latter, the ends of the crossbars extend beyond the attachment point.
Load bars are so named because of their superior ability to carry heavier loads. Because they can protrude beyond the sides of a car, they tend to bump up drag significantly versus an edge bar.
The aerodynamic qualities of your roof-rack setup can have a significant effect on fuel consumption. This is mostly affected by the shape of the load on top of the rack. The aero qualities of the rack would only make a minor difference in isolation.
Aerodynamic crossbars are often installed the wrong way around by users. The perception is that the narrow end should face the wind. This is often not so.
Crossbar designs often disturb air at the front, thus “tripping it up” so it then flows more smoothly over and past the rack with less turbulence. This prevents the vortices from forming that are necessary for Aeolian noise.
In terms of fuel efficiency, a fork-mounted bike rack on a roof rack is likely to be more economical. It keeps the bike lower and more aerodynamic. All bets are off about noise, though, when you start loading objects of all shapes and sizes on the roof.
2. Install A Wind-Deflecting Fairing
As is the case on certain bikes or motorbikes, a fairing improves the aerodynamic quality of the crossbars you already have installed. In doing that, they also cut out most of the noise.
A product like the Rhino-Rack 38″ Wind Fairing improves airflow over and past your crossbars. In turn, this reduces the vortices that form behind them and cuts out much of the noise.
Installation of a fairing offers an excellent solution for anyone who has bought crossbars and is otherwise happy with them. Roof rack noise is not something everyone thinks about before buying crossbars.
3. Padding & Bungee Cords (DIY)
We’ve established that disturbing airflow from the front breaks up the frequency of noise behind the crossbars. This is a deliberate feature in some crossbars, but you can improvise this yourself on a noisy roof rack.
One way to break up noise on crossbars is to use a product like the Dakine Aero Rack Pads. Admittedly, these aren’t ideal for carrying bikes, but they’re great for items like surfboards or kayaks. You can always remove them if you need to install a bike rack.
The cheapest way to cut down noise from existing crossbars is to wrap a bungee cord around their length. This disrupts airflow and prevents noisy vortices from proliferating behind the crossbar.
Video: DIY Wind Deflector With Bungee Cord
4. Remove Roof Rack
People tend to leave their roof racks or crossbars installed because, well, it’s easier to do so. As alluded to earlier, one reason not to do this is that you’re creating more aerodynamic drag, which in turn increases fuel consumption a tad.
There are products out there that might encourage you to remove crossbars (and hence remove noise) when the rack is not in use.
For instance, the Rhino Rack Quick Mount Roof Rack Legs make it easy to quickly install and uninstall compatible crossbars.
5. Adjust Crossbar Position (Where Possible)
The front crossbar is sometimes noisier if it’s positioned too close to the windscreen. Luckily, the position of many crossbars is adjustable, so you can experiment with moving the front crossbar back.
Crossbars like the Stay There Aero Aluminum Roof Rack Cross Bars let you control the distance from the windscreen to the front crossbar.
Of course, you must be careful not to space the two crossbars too close together. This would effectively reduce the maximum weight capacity of the bars. You must stick to any manufacturer’s guidelines to ensure this.
6. Cutting Out Vibration (Loaded Roof Rack)
Once you’ve silenced your roof rack, you can at least leave it in place when it’s not loaded. This is what many people prefer to do. But more noise may materialize once the rack is loaded.
To cut out as much noise as possible when carrying a bike or anything else, check there are no loose or moving parts that might vibrate in the wind.
Make sure that cinching straps have a firm grip on any bike you’re carrying and that the wheels cannot move. Adjust the mounting points of bike racks where they attach to the crossbars. Look for flailing parts, whether they be bike cables or cinching straps.
Items you might need for reducing movement include bungee cords, zip ties, duct tape, and possibly an Allen wrench for mounting points.
