Experiment: smooth wheel discs tested A-B-A - 4.6% mpg improvement @ 65 mph

[markweatherill]

Hmmm, how about using more than one fixing?

[MetroMPG]

Originally Posted by Concrete

yes, the whole test is "on the fly"
when I enter and leave the course - the only thing I touch is the scan gauge

I figured as much, but I wanted to get that tidbit into the thread so others can see the extent you went to get quality data.

Again, nice work!

[Concrete]

If you could find reverse screws and nuts, and kept track of the placement, you could install them so that they are always being tightened when the tires roll in the forward direction.

Well I'm already committed - the epoxy is set... wait a minute!
you are right - pause... running out and inspecting truck...

- the Right and side will want to tightening during breaking and the left on Acceleration.
that would explain my LH front is "clicking" during breaking
and I'm sure I'm breaking harder than accelerating
need to watch the LH for loosening and the RH too - for tightening
could crush covers or puncture my Right front bearing cap that is just under the hub cover

the wheel weights should protect me from too much movement but...
I think I will mark the screw to the cover - so I can note any relative movement easily
and I'll just replace Left front - it is a bit warped anyway - A-B-A-B-A... was hard on the thin covers

Thanks cfg83

[Concrete]

Hmmm, how about using more than one fixing?

I totally agree (that is why I had the disclaimer)
but I was uncomfortable drilling and tapping my aluminum wheels
The plastic hub cover is easily replaceable if/when I screw one up
especially since I was not expecting any real FE gain when I started

still not willing to risk much in this -
I figure I'm up to a 35 tank pay back already on this mod (25 just in the testing fuel)

[markweatherill]

Hi Concrete, I meant use more than one fixing in the hubcap. But I can see looking again at yours that isn't practical. Congratulations on your testing and findings by the way.

[Bror Jace]

Power to you, Concrete, but that sounds a bit too complicated.

I am seriously considering buying these instead:

Full Moon Racing Disc Hubcaps, Stylish Look, Great Prices, AutoAmenity.com

[Concrete]

yep full moons would be great

but right now I am too cheap/broke
and the pay back is only $2-3 a tank even for me and my un-aero wheels & low FE ride

[Bror Jace]

Concrete, No need to justify your methods to me. I'm all on board with the make it/do it yourself bits and pieces.

Problem is, I just can't be boltin' home-made goodies on my 2006 Civic ... it looks brand new and the quality of items I would be able to make just wouldn't look right. If my car was at least 4-5 years old, OK, maybe.

So, I'm ordering those solid hubcaps this weekend.

As a matter of fact, I'll see your cheapskate move and go one better ... desert trays at the Christmas Tree Shoppes for $1.99. They come with a plastic cover (which I'd toss into a recycling bin) and use the flat, aluminized tray for a wheel cover. They're also lighter than a pizza tray.

No, if I can only find some factory-finished rear wheel skirts ...

[Concrete]

I have been putting off the standard deviation calculations
I have a lot of excuses as to why - but really it was just putting it off

There are a lot of ways to do this
- especially since my out bound and return routes are similar but not identical paths

lets do it the easy way

all wheel cover data = ave 29.3 mpg - std dev .63
all without covers data = ave 28.0 mpg - std dev .27

Darin - thanks for the reminder that spreadsheets do std Dev calcs
other wise I would still be putting this off

[Thalass]

Out of curiosity: Has anyone made transparent wheel covers? That way you'd get to still have nice looking wheels while improving your CoD.