External Mirror Removal (with tuft testing)
 

I started a blog recently; read the original article here.

Mirrors are an easy drag problem to spot: they stick out from the car body, disrupting flow. This is easy enough to guess, but how and how much do they adversely affect things? To answer that we need to do some testing.

The Problem with Mirrors

The problem with mirrors is twofold: first, in order for them to function they need a large, flat surface on the back side, which contributes to high drag for the mirror itself. Second, regardless of the drag of the protuberance such as a mirror, when it is brought close to the body of a car the total drag is more than the sum of the two. This phenomenon is called “interference drag.”

You can get an idea for why this is by looking at a tuft test of a window surface behind a mirror. Here’s the flow over my truck’s side window with the factory mirror—which is not large by truck standards—in place:

https://blogger.googleusercontent.co...xi7B=w640-h360
Enjoy the soybean fields. If you follow this blog, you're going to see a lot more of them.

Notice how the tufts are disrupted all the way to the back edge of the window, far behind the mirror. There isn’t much body surface behind that, so I would guess the flow doesn’t clean up at all. Quite an effect from something as small and seemingly insignificant as a mirror!

Smoothing the Flow

Ultimately, we want the flow over a side window to look like this:

https://blogger.googleusercontent.co...gtjW=w640-h360

That’s my Prius, with its nicely rounded A-pillar, laid back windshield, and no mirror. The tufts are nicely aligned and not flapping much, showing little turbulence. How does the truck look if we do the same? Well, not as good—it’s simply not possible to change that A-pillar and windshield geometry without rebuilding the entire cab structure.

But first, here’s the flow with the mirror folded in:

https://blogger.googleusercontent.co...sl5h=w640-h360

Not as great as I had hoped! You can still see a large wake behind the mirror and the flow largely moves upward. Now, here it is with the mirror removed entirely:

https://blogger.googleusercontent.co...bSBv=w640-h360

Ah—finally the tufts have been cleaned up considerably, and the disruption along the bottom of the window has been almost entirely eliminated, with nice, attached flow across it. That’s what we want to see, and after I test for the actual change in drag, I’ll likely make a closeout panel and remove the mirror permanently.

Is Mirror Removal Legal?

This is a modification that gives pause to many who might otherwise consider it. Is it even legal to remove the side mirrors on a car in the United States?

Certainly, removing the passenger mirror is legal; up until a couple decades ago, many new cars were sold without a passenger side mirror at all (they were often an extra-cost option). Now it is impossible to find new cars without two mirrors, even on the cheapest cars for sale today.

Whether it is legal to remove the driver’s side mirror is a bit of a gray area. To sell a new vehicle in the US, manufacturers must ensure that their automobiles comply with Federal Motor Vehicle Safety Standards; included in those standards is a requirement for an external mirror on the driver’s side (companies such as Tesla and Audi are fighting this because they want to fit cameras instead of mirrors for lower drag). Many people think that this means all cars in the US must have a driver’s side mirror—but this is not the case. After the car has been sold to a buyer, its equipment, use, and licensing are regulated by whatever state it is in rather than the federal government—and state regulations on mirrors vary widely. Some states, like my native state of Washington, explicitly require a driver’s side external mirror. Others, like my current state of Illinois, do not. In fact, there is similar language among nearly 30 states in their mirror regulations, e.g. “Every motor vehicle, operated singly or when towing another vehicle, shall be equipped with a mirror so located as to reflect to the driver a view of the highway for a distance of at least 200 feet to the rear of such motor vehicle” (ILCS 5/12-502; emphasis added).

Notice that the way this statute is worded, it does not require side mirrors at all—let alone on the outside of the vehicle! As long as the rear window is not blocked, the interior center mirror satisfies the requirements of the law. If you live in or operate your vehicle in one of these states, you’re good to go with no external mirrors (as I’ve been doing for ten years now on two different cars).

However, if you drive through a state that does require a driver’s side mirror, you will technically be in violation of the law without one. The way many states’ statutes are worded, the mirror requirements apply not just to vehicles registered there but any that operate on its roads—even if you’re just passing through. In this case, you might want to come up with a temporary mirror solution, or if it’s too much hassle for you then just leave the driver’s side mirror on. In the last decade I’ve been pulled over once for no mirror, on my way through Kansas several years ago, but did not receive a ticket. Your mileage may vary, but it’s good to plan ahead based on what you’re comfortable with.

Mirror Replacement

You could absolutely install cameras if you want, but I decided to go more basic. When I removed my mirrors, I picked up some brackets from the hardware store and a pair of blind spot mirrors; their convex surface and placement right next to the window means I have as good a view of my blind spots (if not better) as with the factory mirrors:

https://blogger.googleusercontent.co...FmbI=w640-h360

I'll do something similar with the truck if I remove the external mirrors.

We know what the truck is (because of the garage entry), but you didn't mention it or show a picture of it for those who don't and read the blog.

One minute delta. A next step:

www.gerrelt.nl/wind_noise/a_pillar_deflector/handleiding/Instruction_Manual_Gerrelt_A_Pillar_Deflectors.pdf

side mirror tidbits
 

Here are a few values attributed to dual side mirror drag:
GM, PRECEPT/ EV1,1999, Cd 0.015, ( 9.2% and 7.6% respectively )
Ford FUSION, 2006, Cd 0.015( 4.6% )
Audi A2, 1999, Cd 0.0103 ( 4.37% )
SPIRIT-I, 2014,w/ Toyota OEM dual mirrors, Cd 0.0235, ( 9.63% )
SPIRIT-I, 2014, w/ Toyota OEM dual mirrors folded, Cd 0.175, ( 2.45% )
SPIRIT-II, 2017, w/ SCCA racing mirrors, Cd 0.010, ( 2.98% )

Hmm... I just might have to try this with my car. Seems pretty straightforward.

Things are quite different in my country. Even though I have seen some Mercedes-Benz trucks and that Audi e-tron with rearview cameras and no exterior mirrors at all, for most vehicles here having 2 mirrors is mandatory. And even some cars which were available with only a driver-side mirror until '98 are easier to find already fitted with a passenger-side mirror.

1991 Toyota 4WD pickup
 

Here's one image
https://www.edmunds.com/toyota/pickup/1991/review/

The legality of mirror deletes is definitely a concern. Saving money on gas, just to pay it back in traffic tickets, is not very productive.

That said, where I live (Florida) state law requires 2 mirrors. You either need a driver side exterior mirror plus an interior rearview mirror, or you need exterior mirrors on both sides.

So I could legally delete the passenger side mirror. But deleting the driver side mirror could cause trouble. However, I see lots of vehicles driving around with illegal modifications. The police don't seem to care, unless they have nothing better to do.

Unless some commercial vehicles to which visibility would render an interior mirror pointless, AFAIK it's mandatory for all cars in my country regardless of how many exterior mirrors they're fitted with. And even though reverse cameras became quite common, either as a factory fit or aftermarket accessory, an interior mirror is still mandated.

I have a technical question: back when I lived in California, the law actually stated that a vehicle must have a device that allows rear vision for 100 feet on the drivers side of the vehicle. An austin mini traveler wagon from britain, rhd, complied so there was no mirror on the passenger (left) side.

Had to have been a one off exemption.

.

“Tiny mirror” for the win... ;)


https://ecomodder.com/forum/showthre...ror-23623.html



:turtle:


>

.

Meanwhile in Brazil, AFAIK the rare RHD imports were mandated to have both exterior mirrors. There is at least one RHD VW Beetle which was imported by a diplomat from Mozambique in the '60s in São Paulo, and it had exterior mirrors on both sides. And even though most of the regular LHD Beetles that i still see on the wild feature both exterior mirrors, recently while walking the dog I saw a '95 Itamar with just a driver-side exterior mirror.

Back to the RHD issue: even though it could be legal to drive one without a left exterior mirror, I wouldn't be so willing to try.

'passenger' side mirror
 

1) For $36 I added a passenger side mirror to my 1984 CRX.
2) At that time, it was quite common for automobiles to have only a single mirror.
3) My Rambler American had single mirror.
4) My Morris Minor 1000 had single mirror.
5) El Camino had single.
6) My Karmann-Ghias had single mirror.
7) VW Transporter had two.
8) Dodge D-100 had two aftermarket mirrors.
9) T-100 has two.
Some 'historian' may be able to peg a date when the DOT/ NHTSA began to 'mandate' the second mirror.

What year and model? I had a 1959 Rambler 2-door station wagon in college. IIRC the last year of the flathead six.

year/model
 

It was a 1961, two-door sedan, with flathead-six, one-barrel, no oil filter, and three-on-the-tree. 25-mpg. $ 80.
I overhauled the engine in high school auto shop, and drove it until I got orders for overseas.:)

Aluminum extrusion door window frames? Identical front and rear bumpers? Carb bolted to the head? Exhaust pipe clamped to the block?

I drove mine for 2 years, no maintenance except welding a broken clutch bellcrank. :thumbup:

An evolution of Nils Wahlberg's 1949 Nash Airflyte.

engine
 

'cause I was and remain 'stupid', I created 'headers', consisting of three exhaust pipes, down underneath, to three cherry-bomb glass-packs.
And a Stromberg, two-barrel, on top of a Pep-Boys siamise-ed aluminum adaptor.
On Wednesday night, on Van Nuys Boulevard, with the ignition retarded just a bit, no one knew what was under the hood, and no one was adventurous enough to 'experiment' with the unknown. Funny!

Good times. :)

Hmm odd fire loud as poop engine noise. Wouldn't mess with you either, like somebody who rolls up engine off.

Wednesday night, parked down by BOB's BIGBOY, before all the lightpost mods. I miss that along with CHP harassment on the 405 northbound of the 101.

In Brazil it used to be still "acceptable" for the cheaper econoboxes to feature only one exterior mirror from the factory, yet some fleet-oriented versions of the VW Santana and Chevrolet Opala which were considered prestigious cars in Brazil could be specified with only a driver-side exterior mirror. Last time I saw a Santana from the '80s with a single exterior mirror was about 8 years ago. On a sidenote, a few days ago while walking the dog I spotted what may be the last '96-'97 Ford Fiesta with only the driver-side mirror in my hometown...


Not sure when utility vehicles were mandated to come with exterior mirrors on both sides in Brazil, but most likely it was still in the '60s, yet the stock ones fitted to many medium-duty trucks until the '70s were so small that aftermarket ones which used to be of the same size more often found on modern medium-duty trucks were quite popular. Once in a while I even see some VW Transporter or Chevrolet C-10 fitted with such mirrors.

Bob's Big Boy
 

My two brothers and I actually went to the Bob's, on Sherman Way, in Canoga Park in a 'race car.'
It belonged to my middle brother's friend Craig, a '56 'Van Nuys' pillarless Chevy two-door.
They'd just run it at Lions Drag Strip, towed it to our house; the owner took off on my brother's custom Zundapp motorcycle, and we restored the driveshaft and took off for Bob's drive-in, with open headers, loping in to a spot.
After we ate, we pulled onto Sherman Drive, heading towards Fallbrook Avenue.
On the one-two shift, the front wheels came off the ground. My oldest brother was riding shotgun, and we thought he'd soiled himself!
I can't believe we weren't arrested.
It's amazing that we survived our youth.:p

Reminds me the day I tried EOC in a downhill stretch of the BR-101 when I was 17. No power steering was not much of an issue, but the lack of vacuum for the brakes made me regret it. At least I wasn't involved in an accident.

Good point; I changed the blog post to add the make and model year.

some 1993 Toyota p'up data
 

I recently drove a friend's '93, 2WD, 22-R, M-5, cab-high aluminum topper, with nasty roof rack, holding garden trellis, topped-off, from Denton, TX, to Fayetteville, Arkansas.
Bed and tailgate was fully-loaded with metal yard furniture and garden tools.
I tried to hold it at 100-km/hr. No official weight.
The truck has HANKOOK H-rated tires @ 44-psi all-around.
Temps were in the 40s-F.
Wind blew the entire trip. Trees stripped of leaves, and no windmills or flags made it tough to estimate wind direction/ magnitude.
I didn't run any electrical accessories or A/C.
At 322-miles I chickened out, and turned of the highway for fuel.
Tank mileage was 28.2- mpg.

Are these values for “dual side mirror” or for the addition of a second mirror?

It sounds like replacing the stock mirrors for the racing ones, while keeping at least one mirror at each side.

dual or second
 

All values are for dual mirrors.

potential disadvantage...
 

Like Vman455, I've been rolling with various exterior/interior mirror configurations for many years now (15?). Currently, on my Mirage, I've replaced the outside mirrors with internal convex ones placed close to the glass.

Another potential disadvantage: while interior mirrors preserve much of the side view (some even expand it), you lose the ability to look directly down the side of the car itself. That can make reversing into tight spaces a real challenge.

Also makes it harder to spot cyclists when pulling away from the curb in a line of cars, if the cyclist is riding close to the cars.

You would of course adapt for safety's sake (eg. with exaggerated shoulder-checks, or cracking open the door when reversing in close quarters).

But I'm planning to modify my outside mirror blanks to add exterior mirror "slivers" - mostly to aid reversing into tight spots (by tight I mean just inches to spare from the side of the car).

Retractable/pop-out mirrors would also be fun... and more aerodynamic.

So approx half those figures for removing the passenger side mirror? Is the juice worth the squeeze?
I’m not trying to be smart, I just wonder how such minute changes translate to mpg’s.

approx..............wonder
 

* Yes ,the values imply a 50% reduction from losing one.
* Right! With a Cd 0.80 JEEP CJ from the early 70s, you're not going to see any remarkable difference. Volkswagen's XL1 would be a different tune.
* A good reason to noodle on a vehicle-specific basis.
* I'm a big ' safety first' advocate, and personally, will suffer higher drag for the sake of good situational awareness.

There is no magic bullet. But many small changes = magic buckshot.

In 2006 (wow, that's a lont time ago!) I did A-B-A-B testing on my 1.0L Firefly (Chev Metro) and this is what I saw:

https://www.metrompg.com/posts/photo...or-chart-z.gif

Testing details here:

Reflections on side mirrors: testing drag vs. MPG

Same here. I like to improve my car's fuel economy, but not at the risk of wrecking the car. IMO that's a false economy. If you do a lot of city driving, backing in & out of parking spots, etc then having usable side mirrors is a must.

That said, I'm currently testing motorcycle mirrors on the Prius. They're about half the size of the stock mirrors. So the drag reduction should be similar to deleting one of the stock mirrors. But I won't lose a mirror. IMO that's the best compromise between drag reduction and safety, for my driving conditions.

A test such as this one would be interesting, to see just what the difference in drag between the two mirrors is. (Just because it's half the size doesn't mean it's half the drag).

https://i.postimg.cc/YCVXVtsz/Figure-5-7.jpg

Clever.

Fortunately, here in Oregon, the code is relatively open:

"(2) A rearview mirror or device only
meets the requirements of this section if it
enables the driver of the vehicle to have
such a clear and unobstructed view of the
rear at all times and under all conditions of
load as will enable the driver to see any
other vehicle approaching from not less than
200 feet in the rear on an unobstructed road."

I can't reliably measure how much of an impact it has had on my i3 to remove the exterior mirrors without driving 1000s of miles, but aside from an absurdly wide 110 degree view on each side, the camera pods I installed work well for me. They eliminate the blind spots of the interior BS mirrors, and stupidity would be my only excuse for curb rash or cutting in front of a bicyclist now.

I have the STL for the fender mounted camera housings posted here.

Those look really good!

I've got my interior mirrors angled so as soon as a car or cyclist moves out of view of the center mirror, it shows up in the side mirror. As a cyclist myself, I think I'm more cognizant than the average driver--having dealt with so many stupid drivers in the past (including being hit by someone failing to yield the right of way).

The biggest issue I found with BS mirrors was when parallel parked with another vehicle behind. There simply is no seeing past it without pulling out a bit. Not a big deal mostly, but requires extra caution.

Some cyclists, mostly the so-called "bicycle activists", lack the common sense and seem to expect every driver out there to predict everything, even while they come from a blind spot acting as if they owned the road.

what about lowering the mirrors to just below the window and adding transparent fairing to the mirror side?

That might not work for the offside mirror.

Alternates would be on the front fenders, peep mirrors or those bus mirrors on stalks. Anything to get away from the A-pillars.