Starting to aero the Subie.

[Xringer]

Originally Posted by MetroMPG

Even notwithstanding that you discovered the rack "rails" aren't perfectly parallel, it's not completely true.

Remember we live in a world of cross winds, so much of the time the racks present a larger surface area to the apparent wind and generate more drag than one might think at first.

That's the main reason I would encourage people to remove their entire rack if it's not regularly used (and not ridiculously difficult).

My roof rack get so much use, I would lost without. It's what allows my CRV to carry long loads (12 foot lumber, 10 foot rugs etc).

It looks pretty aero to my eye. Compared to my old square windsurfer rack, these things are great.. And compared to the ones I used back in the 70s that made that super loud humming sound, these are perfect!

I'm wondering about crosswinds. If a crosswind is hitting the side of the car,
90deg off the direction of travel, I can't understand how it will hurt MPG...

[MechEngVT]

Originally Posted by pasadena_commut

Is the inside edge of the mirror clear of the passenger side airbag at maximum expansion?

I'm pretty sure if there's an airbag-deployment collision nobody will care if the mirror is knocked off.

Also airbags tend to deploy toward the occupant, then expand sideways to fill out. It would probably either knock the mirror through the side window or through the windshield, if not just crush it in place.

[MechEngVT]

Originally Posted by Xringer

I'm wondering about crosswinds. If a crosswind is hitting the side of the car,
90deg off the direction of travel, I can't understand how it will hurt MPG...

Because you will have to drive with your wheels turned into the wind to maintain a straight heading. To drive in a straight line the force vector generated by your tires must exactly oppose the force vector generated by your aerodynamic drag. If you're traveling straight at 50 MPH and there is a 10 MPH cross-wind perpendicular to your travel, your vehicle sees an effective wind of 51 MPH at an angle of 11.3 degrees from your direction of travel. You must then turn your wheel into the wind to generate lateral force to oppose the cross-wind. This increases your rolling resistance since you will be traveling straight even though your wheels are slightly turned (operating at a slip angle). Since lateral tire forces apply perpendicular to the tire, any time you turn your tires the force that pushes your car sideways also opposes its forward motion by pointing slightly rearward.

Heavy truck manufacturers evaluate the aerodynamics of their trucks in wind tunnels by setting the truck at an angle to the air flow. I can't remember what angle they use, but they've determined the statistical wind profile that vehicles are effectively always at something like an 8 degree angle to the wind or something like that.

[Xringer]

I see.. I was aware that I had to make corrections, but didn't think of them
as being held for long distances.

I guess a "10 MPH cross-wind perpendicular to your travel" is only good when I'm on a windsurfer.

[brucey]

The mirror is just on a piece of metal bent and wedged into place behind the speaker there. The overall view is smaller, tinier, and not as focused, but I can still see whats there without the outside mirror. I'm keeping the outside mirrors (but folded in) because backing up this boat in tight quarters is near impossible without them.

[pasadena_commut]

Originally Posted by brucey

The mirror is just on a piece of metal bent and wedged into place behind the speaker there. The overall view is smaller, tinier, and not as focused, but I can still see whats there without the outside mirror.

Is it better than one of the multiple mirror rearview mirrors? For instance, this one (not that I have it or endorse it, it's just an example) :

Day Night & Blind Spot Rearview Mirror

Most of the multiple view rear view mirrors lose the day/night function, which makes them awful at night, but the one above has retained this feature, at least on the main mirror. I tend not to use the side view mirrors at night in any case since it is tough to judge distance from a pair of glowing spots.

Originally Posted by brucey

I'm keeping the outside mirrors (but folded in) because backing up this boat in tight quarters is near impossible without them.

The folded in position on the external mirrors isn't terribly aerodynamic. When extended the mirror sits on a stalk of sorts, so that some of the air can flow along the car body between the mirror and the car. When folded in I think the mirror will disrupt this flow. Also in the folded in position the leading edge of the mirror isn't very aerodynamic. While completely removing the side mirrors would definitely reduce drag, it isn't clear that folding them in will.

[brucey]

They're not aerodynamic at all, but neither are they in the stock position. They are completely flat facing the wind, essentially truck mirrors. The only real difference is its shrinking how much they stick out into the wind. There is actually a noticeable change in wind noise in the car with the mirrors in. I'd love to have them gone, but backing up a 4000lb car is hairy when you can't see the edges.

Also, I have one of the oversized convex mirrors, it works fine. At night its no trouble because the headlights can't get focused on your eyes. In fact, thats all I really need. The other mirror is there just for back up.

[brucey]

Yay!

I'm going to be doing a bunch of tests now. starting with the mirror difference.

[bhazard]

Neat. Now you can still do fuel logs at fillups, and start doin trip logs with the scanumagauge/

[pasadena_commut]

Originally Posted by brucey

Wifey: What time is it?
Brucey: 28.9 MPG!