Thoughts on wheel covers...
 

What's the consensus, is it the reduction of the volume of air that passes through them that is cut off/reduced (i.e., closing up the spokes and sealing them), or that they are flat (which does the same of course, but with the added benefit that they are flush to the tire) that is responsible for the drag the reduction?

I'm contemplating modifying my existing hubcaps by simply filling in the "spokes" and insuring no gaps between the hubcap and the tire, but this won't make them flush.

Trial it with duct tape, it will give you a ballpark of what you can expect, but minimal cost and time
invested.
Some cars have better results than others with respect to wheel covers.

Taped up the spokes, we'll see how it goes across this tank...report in a week.

Mostly closed is good, and flat and closed is better.

consensus
 

I've yet to read a complete discussion on wheel covers.
Observations have been reported and recommendations.
*An open wheel has no surface with which to 'support' airflow,so a solid surface is needed.
*A slightly convex disc won't 'tin-can',is extremely rigid for it's mass,and has a measurable drag advantage over a flat disc.
*Brake cooling should not be ignored,however solid 'MOON' style wheels have shown to be no disadvantage for many members including myself.
*The knock-on style covers are noisy and eventually come off.I've written them off.
* I was able to scrounge up a set of covers from a 1975 Buick Electra.They are absolutely 'silent,' securely hold to the wheel,and have modest ventilation for brake cooling.
*Many members have found covers which stay firmly attached which can be modified aerodynamically.

Flat coroplast circles zip tied around the spokes work well.

MetroMPG probably has an ABA test on wheel covers somewhere. I'm not sure of the % improvement but wouldn't expect more than 1mpg.

wiki link to wheel covers and data:
Smooth wheel covers - EcoModder

5 users did aba testing and got 1-1.5 gain or 2.4%-4.6% gain. not to shabby for an easy cheep mod

Well first tank down...big gain. Saw highest MPG yet, 35.88.

I simply taped over the spokes as the test. I'm working on a permanent solution:

http://www.mulsannescorner.com/pictu...2018.06.06.jpg

looks like a good start, what were you running before this tank?

The 16 week average prior was 33.59.

Curious, are there any concerns about brake temperatures closing off the wheel? I suspect most of the cooling ventilation comes through the spokes in the hubcap, but what amount of brake cooling does a road car really need? I drive a Versa after all; this isn't a car for spirited driving. Should I have any concerns about brake cooling blocking off the spokes? My 42 mile one way commute is board flat and has about a dozen braking points, only 1 or 2 of which I would consider heavy (braking on the interstate exit). The rest are 25 mph or less braking zones one tends to find in any neighborhood in the country. Sure, there are those typical emergency braking events, but nothing sustained. Plenty of people here have gone the flat/covered route, thoughts?

woodstock74:
do a quick search for smooth wheel covers on the site, or look through our wiki page, all your questions have been answered in depth before.

I've read the Smooth wheel cover Wiki in depth and about as indepth as it gets regarding brake cooling is, "it may block air flowing to your brakes." I'm looking for real world experience, not supposition of what I already know: Yes, my brake cooling will be affected, but how important is that really on a road car? I'm not doing any sustained braking, and couldn't the argument be made that with a reduction in cooling flow my optimal braking temperatures will be reached sooner?

In my car it has not had any negative effects. 30,000+ miles covered and when i get new tire last month they said the OEM breaks had 1/3 life left. now I do not use the breaks much but when I do I am ok.

The issue is long term heat build up. are you racing to stops? start then stopping several times in a 3-5 min period? are you towing? even in the mountains I was ok, they got warm but held and worked fine. in 95% of hypermiling driving you will be ok.

Brake cooling? I recall reading a statement that when they were testing the intrepid as a police vehicle the test was multiple runs at WOT to 100mph then hard on the brakes to a complete stop, immediately start again. After I think 3 runs the brakes were glowing and one test car actually had something in the wheel well catch fire. They revised the brake rotor for better cooling. Obviously you would never get your brakes this hot, unless you plan on driving like a hell-bent moron you'll be fine.

As a hypermiler I work very hard to avoid needing to brake at all. As such, brake cooling is so far down my list of concerns it's not worth considering. How many emergency braking events do you have in a normal drive? Even if you have one, you're not likely to power up to 100 and brake down again immediately after the fact.

Just to test one time, I arrived at work after my 10 mile commute. I reached around and was able to comfortably brush, then touch, then GRAB the brake rotor with my bare hand.

This is why I stuck with OEM wheel covers.
I used chevy luminia wheel covers and these wheel covers were used on luminia cop cars.

My brakes get used quite a bit with a trailer.

Thanks for the reality check everyone!