Why Outer Wind Deflectors are Better
This is one of those long-time debates on vehicle forums: Which are the better choice – the “outside-type” stick-on wind deflectors, or the “in-channel-type” friction deflectors? Well I’m going to explain my personal reasons for picking one or the other, but ultimately you pick whatever you want to use on your truck. (Note: my comments are based on the Crew-Cab, 4 door deflectors; Some of the text below might not apply to a King Cab application)
TLDR: I prefer the outside versions better, and I have 4 reasons to reinforce my preference:
1. The ‘Outside’ versions simply look better.
First, look at how the outside versions flow better with the window frames and body lines (see image below). I don’t like how the in-channel rear deflectors cut off at the back! The short length makes them look like they’re too short and stubby, and for some reason, they look like someone stuck a pool noodle on their window frame. On the other hand, I like how the stick-on versions are full length all the way across the width of the glass (not just the part that opens). It just looks more uniform to me. Take a look at the photo below to see what I mean:
2. The ‘Outside’ versions are (probably) quieter than the in-channel version.
Okay, I’ll be direct here: I did not actually take dB measurements to compare the wind sound level between the outside version and the in-channel version, which is why I said “probably” in the title of this bullet point. However from personal experience, I have ridden in a Frontier with the in-channel deflectors, and the butt dyno (ear dyno?) told me that it was noisier than when I drive my truck. Take it for what it’s worth.
Let’s look at it from an aerodynamic POV: as shown in the “Outside Version” part of the photo above, with the outside-style deflectors, the outside air will hit the A-pillar, then get routed around to the sides of the truck. From here the air will hit the wind deflector, and the wind deflector will smoothly route the air away from the window and out to free space. That’s it – the wind only hits two things on its way past the truck.
Now think about how the air passes by the in-channel deflectors. The outside air will also hit the A-pillar and get routed around to the sides of the truck. However, from here th air has to pass over the high-friction rubber window trim first, then it will pass over the significant gap between the window trim and the in-channel deflector, and then the air will hit the actual in-channel deflector. It will follow the outside shape of the in-channel deflector (which oddly curves back inward towards the window glass!) and in the end, the air (and all of its noise) will end up in near proximity of the window glass. I’m not a scientist or an aerodynamic expert, nor do I play one on TV – but what I just explained should be easy enough to understand: basically the more things the air hits, the more noise it will make. Also note that unlike the in-channel style, the outside-style deflectors reach out farther away from the vehicle, routing the air (and its noise) farther away from the vehicle, and that means less noise overall.
3. The ‘Outside’ versions do not interfere or cause issues with window operation and fitment.
This isn’t a myth: in-channel visor/deflectors are known to cause issues in general, regardless of vehicle. In-channel visors have existed for decades now, and they all get installed the exact same way: open the window, find the slot where the window goes at the top of the door frame, and jam the in-channel visor up in there. Think about that for a second – there is a specific slot on the vehicle designed to a specific size to accommodate the specific width and thickness of the window glass… and you’re jamming something else in that slot, hoping it will co-exist with what is actually supposed to be there by itself!
So where does this cause problems? The most common one is “sticky windows” where when you try to roll down your window, the window gets stuck in the window frame because (hello) it’s wedged next to a piece of visor/deflector plastic. That means the window regulator motor has to use more power to “unstick” the window – and guess what: window regulator motors are not designed to apply torque like that! Window motors are only designed to lift the weight of the window, and that’s it. The window regulator motor can easily burn out if they are forced to try to overcome that added resistance. Another thing to consider is sealing effectiveness; most vehicle window frames (and the window channels) are designed to create a nice, even seal with the glass. When you wedge something in between the glass and the rubber seal that isn’t supposed to be there, that changes the interface between the glass and the seal, and this can actually introduce small gaps. These gaps can allow things like wind, dust, rain, etc. to pass into the interior (or into the door panel itself). To be fair, not all vehicles with in-channel visors/deflector experience these issues – but the issues do happen a lot, and are well documented.
4. The ‘Outside’ versions are actually attached to the truck.
Looking at the genuine Nissan OEM vent visors as an example, Each vent visor is secured to the vehicle in 3-4 different places (4 for the front, 3 for the rear on a Crew-Cab version). The primary attachment point is the single, continuous strip of double-sided tape that sticks to the outside of the window frame. Not only does this attach the vent visor to the body of the vehicle along the entire length of the visor, but its continuous seal keeps noise down by not allowing any air to fly through in between the visor and the body. The secondary attachment points are 3 small metal clips that – yes – slot into the window frame. Now, before you think that I just canceled out my #3 statement above, know that these metal clips are less than a 1/4″ wide and barely 1/16″ thick… nowhere near the same size of a typical in-channel vent visor, and zero chance of affecting the window seal interface. The actual purpose of these clips is to help the outside vent keep its shape, ensuring that wind is channeled as far away from the window and vehicle as possible at any speed.
TIP #1: Speaking of double-sided tape, to make sure the outside-style vent visors stay securely attached to the body, don’t just peel the backing and stick them on. If you install double-sided tape without correct surface prep, there is a 99% chance that one day you’ll lose that vent visor becuase in due time they will fall off or get blown off. On the contrary, I have had my outside vent visors on since the day after I bought my truck in September of 2014, and because I did the correct surface prep they are still as securely attached to my truck as they were on the day I installed them. The trick? No tricks really, it’s simple – you just need three things: isoproyl alcohol, microfiber towel, and a heat gun (or hair dryer).
To prep the surface of the window frame, first make sure the truck is clean (the best time to install outside vent visors is right after a good truck wash). Using a new, clean microfiber towel, splash some isopropyl alcohol onto the towel and wipe the actual surface of the window frame where the double-sided tape will be touching. You don’t have to push hard or scrub – just wipe the area in one continuous motion in one direction. Wipe in 2-3 passes, then allow the surface to just naturally dry on its own. At this point DO NOT touch the door frame area that you just wiped – if you do you can easily leave the oils from your fingers onto the surface; this will reduce the effectiveness of the adhesive on the double-sided tape.
From here, it’s time to install the vent visor. Peel the red backing away from the double-sided tape, use your heat gun or hair dryer to slightly heat up the tape (don’t burn it if you’re using a heat gun!), then stick the vent visor in place. That’s it! Allow the vent visors to reach maximum adhesion before driving (wait about an hour, that should be more than enough time).
TIP #2: I highly suggest that if you go with the outside-style deflectors, try to get your hands on OEM Nissan “Side Window Deflectors” (Nissan part #999D3-BT001CC); they are discontinued, but there are still some sets available out there. IMO these are the best outside-type deflector to buy, designed specifically for the Frontier. As I explained above, the OEM Nissan visors include metal in-channel clips. The clips not only help keep the the deflectors in place, but the way the clips are, they also keep the deflectors in the correct position and spacing from the window glass. I’ve seen some aftermarket visors/deflectors on other cars where the unsupported middle section of the visor would start to “droop” inward towards the window after a few months due to sun, wind, or whatever. With the OEM metal clips, the OEM deflectors stay in place.