We need a hotline to the engineers …

Greetings all. I have a question related to the side mirrors. It probably doesn’t deserve its own thread but my curiosity is getting the better of me. I noticed in the photos in this post a detail: a row of 4 tiny tear-drop-shaped bumps along the top of the mirror. I took a photo of my mirrors to highlight the bumps:

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These bumps are no bigger than a grain of rice. What could their purpose be? Surely not aerodynamic. They are so small. So what other function could they perform? Purely decorative? Any ideas?

And while we’re at it, why is it that we as customers don’t have a direct line to Toyota engineers to get questions like these answered! While we have their attention I’d sure like to know what that detail on the center console in front of the gearshift is.

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They add 10 HP.

Honestly, though, I'm curious as well. I wonder if they have some sort of aerodynamic purpose, or if they were just put their for cosmetic reasons.

 

Small things like that are usually added to reduce wind noise.



It's an added "feature" to say they have many features like the 1984 graphics info screen in my 2019.

 

It's just a little storage spot for junk to accumulate. In the SR5 models that area extends all the way to the passenger side so it's quite a bit bigger and fairly useful for holding spare change, chapstick, etc.. Something you TRD guys give up so you can manually play with your knob. You also lose out on the sunglasses storage compartment.

 

Vortex generators...reduces global warming!!!

 

Those little nubs are used to cut down on wind noise/droning (in theory). They break up the flow of air so you don't get vibration or harmonics over that Plastic. I don't know how effective they are on our mirrors completely but slightly larger ones on a lumber rack etc do wonders. As for the little tray, someone on here showed it fits Oreos PERFECTLY! (There is a whole thread on here about that little tray). Above is right, it is usable for pens etc on the SR5 but on the TRD, it is relatively useless. I like playing with my knob vs turning a dial ever since one of our Taco brothers had his dial fail on the trail haha

 

That’s for storing quarters and ass pennies so when you hit a bump they get jammed into your gear shifter slats. Or if some homeless guy sees 40 cents in change out in the open in your truck, he will smash a $400 window to get at it.

 

Ass pennies! I forgot about that one! Haha

 

Sauce Holder

 

Same concept as the spiral pattern on car antennas.

 

What’s your point? ;-D

A very official-sounding explanation and I like your thinking, but I just can’t buy it. 4 little grains of rice? Spaced apart like they are? Nope. Now if they were bigger, or if there were many in a row, or a field of them like dimples on a golf ball, I might agree.

 

File them off and find out.

 

Well, you'd be wrong. A gold ball is a singular surface and depending on the spin or movement of the ball, its surface can affect its trajectory based on the close grouping of dimples, where with the mirror it is affected by multiple vortices coming from multiple directions at varying speeds with with the solid traveling in a singular direction. They simply help clean up the air as it passes over the surface. Less is more here. Is it absolutely necessary? Probably not in every day use, but it keeps whiny people from complaining about a barely detectable whistle or drone to the manufacturer. Trust me, the Japanese wouldn't add something that didn't have a purpose just 'cuz.

 

Those 4 little nubs don’t seem to be big enough to have much effect, but the science of fluid dynamics and acoustics is pretty complex. It’s pretty important to car companies to reduce interior noise and mirror vibration at speed and lots of studies are done. Here’s a couple.

https://www.sciencedirect.com/science/article/pii/S1110016821004129

https://www.researchgate.net/public...ffects_on_an_Automotive_Rear_Side_View_Mirror

Maybe Toyota’s testing or simulations found the nubs do make a difference in reducing turbulence and noise. But I bet it’s overwhelmed by all the racks and external junk we put on our rigs.

 

Those nubs are there to let people know if you replace your mirror with an aftermarket one without 'em, you chintzed out, and your warranty is probably voided.

 

You’ve got them on the tail light assembly too.

 

Little storage cutout is perfect for a roll of poop bags. Between that and the rear window, these are great dog dad cars.

 

Well. Access to Toyota engineers is not required after all. We have plenty of brain power right here on this board!

I filed off the nubs and went for a test drive on the highway.

Here are the results of the test:

• 40 mph: a low hum starts to develop.
• 45 mph: the mirrors start to sing opera.
• 50 mph: high frequency vibration of the mirror glass.
• 55 mph: the mirrors are howling like banshees.
• 60 mph: the steering starts to feel a little light.
• 65 mph: mirror housings begin to oscillate wildly.
• 70 mph: the mirrors are louder than the crawl control.
• 75 mph: the front wheels leave the ground.
• 80 mph: the mirrors fly off, spinning into adjacent lanes of traffic.

Conclusion: the nubs are spoilers which defeat the tendency of the mirror housings to act as lifting bodies.

Thanks everyone!

Hey buddy, have any idea where I can lay my hands on some of those cheap replacement mirrors?

 

I’m sure it’s a very subtle effect (and they’re certainly not there to increase downforce or improve handling), but they are indeed there to disrupt the airflow over the mirror to reduce wind noise and drag on the mirrors.

I’d wager that filing them off or replacing with a smooth aftermarket mirror would have a minimal and possibly even not noticeable difference (over all the other things that result in wind noise on a 4R). But if put it in a wind tunnel you would see the impact.

If you want to confirm with Toyota, you could always shoot them an email; maybe get lucky and get a response with a more official answer… but I’ve seen this discussed numerous times over in other areas, including having read through a very long and drawn out analysis of effects of noise and drag of mirrors on commercial vehicles.

Search mirror bumps and BMW; you’ll see this discussed a few times in beemer forums.

 

What is your explanation?

 

My QX70 had Dumbo Ear side mirrors. They’d whistle when wet.

The mirrors on my 4Runner make no noise.

 

I had an old BOF Explorer and there was no noise from the mirrors. The engine noise might have drown it out but that’s another story

 

That's exactly what I use that space for!

 

Exactly what I use mine for!

 

Yeah so I can find out who to thank for sloping the back of my 4Runner so when I open the back hatch all my tools fall out. I love it when my tanks of map gas get dented and can’t stand up anymore. I mean who doesn’t want their torch tip smashing on the ground. Especially on a rubber roof. Fucken idiots them guys.

 

No, we really don't need a direct line to Toyota engineers. They may decide to get the hell out of the automotive business for good.

 

(Shhh. Tonight drive down the alley behind a 7-11 and swipe a couple of milk crates. Put them in back and put all the loose stuff in them. It’s the time-tested solution to your problem. It’s a bonus if you can find ones with the steel reinforced rim.)

 

I’ve wondered if the mirror nubs are to disrupt airflow so the air doesn’t wrap over the top and get behind the mirrors causing the mirrors themselves to vibrate (not the housing). Just a guess.

Isn’t there something on the bottom as well?

 

@Bwery lower the rear window and come back and tell us what you think again