smooth wheels/hub caps = MPG increase?
 

I'm looking to hear from anyone who has kept THE SAME tire size, but either added smooth (plate/dish-like) hub caps to the wheels OR found the same smooth type of wheel to replace their pre-existing ones. I would like to know if this change resulted in increased MPGs.

I swapped my stock CRX HF (steelies) rims for a set of those superlight Mazda Miata BBS (mesh-style) rims. The BBS are in NO way a smooth pattern; they probably stir up all kinds of turbulence. Although I love the look of the rims, they (along with their somewhat LRR & lighweight tires) didn't boost my fuel economy. Now, I don't know if there's a chance that any gain may have been offset by the fact that the wheels are not as smoothly patterned as the stock steel HF rims. I do know that I'd just like to hear from anyone who HAS deliberately swapped to a smoother wheel pattern...and whether or not they experienced a gain/loss in FE. Thanks a bunch for any/all info.

Try googling "Baby Moon" hubcaps. They are aerodynamic, originally deigned for racing.

Take a look at this post...
https://www.gassavers.org/showpost.ph...99&postcount=2
in the image you can read...
"We also tested the moon discs which reduced drag by two to four counts. The farther the wheels are from the outer edge of the fender, the less the discs matter."

this is what i've put on since a couple of days they came from my dad's old ascona that's due for the scrapheap.

https://www.fuelly.com/attachments/fo...125ac5fd1f.jpg

don't know if they're helping... the car feels a little different but that might just be from the extra weight or because i know they're on.

they don't inhibit cooling if that should be an issue but they're pretty clean otherwise... they also make car car look more modern than it is :)

Any chance to put those stock HF steel wheels on a scale and compare them to the alloy wheels you have?

Sure...
 

I actually did put them on a scale. The stock HF wheels are 13" X (4.5?)"...anyway, they weight in at just a hair over 13LBS., if memory serves. (I will weigh them again both with and without the little "H" caps).

As for the Miata BBS rims, they're definitely lighter, by 3LBS or so...and larger too. The Miata rims are 14" X 6"...and the tires I got for them were Nokian's that came off of a Prius :thumbup: The tires are 175/65/14's that are even lighter than the tires that were on the HF steel wheels. I did my homework on this swap! The Nokians can also handle 50psi, no problem -(not that I wasn't already doing that with the Aquatred-3's that were on the HF wheels...I was!).

Road Warrior, thanks for that link/article. I sure hate it when good looks pose a threat to FE. Well, I suppose in order to find out whether or not my new, lighter wheel/tire combination had a net ZERO effect on gas mileage (i.e., lighter overall combination with possible aerodynamic drag = no FE change?), I'd have to find a different wheel/tire combination of equal weight, but WITH a smooth flowing pattern (and keep certain that they remain an equal distance from the wheelwell when mounted on the car). That should tell the tale. **OF course, there's always the chance that dropping a few LBS from the (front/ FWD) rotating masses just HAS NO change with this car...as the OEM wheel/tire combination was not a tremendous amount heavier.

Sludgy -

I used to google that, but "racing disk" is probably better. This ain't cheap, but these are the real deal :

Moon Discs
https://www.mooneyesusa.com/Store/in...2de15d5fb11671

CarloSW2

Since you have lighter wheels/tires, have you tried shifting gears at lower rpms? The ligher wheel/tires should let the car accellerate easier.
I've noticed a slight difference when I installed a lighter flywheel on my car.

prolly lost a bit of torque in swaping flys tho...
should rev faster and slow down faster but torque is lost

oh my chevette i have almost baby moon hubcaps and then i have the stock windmills. it doesnt make a difference either way. of course the cars high up and lot of frontal tire space, but also very skinny frontal tire space...

All these flat and moon hub caps and covers sure are expensive. Wish i could find a used set for cheap. Doubt thats going to happen though. Has anyone ever tried to make their own? Out of plastic maybe?

$69 a set.
https://www.autoenhance.com/trimr.html

Lighter wheels should show the most difference with acceleration/deceleration and suspension. Which lends itself to increased FE in heavy stop/go City traffic I suppose. Once at speed...I don't see how it can make much FE difference. I could be wrong.

I too am curious Brian about how much JUST a racing disk installation changes FE.

Craigslist for the 14 inch at 50 for the set: https://stlouis.craigslist.org/pts/611297722.html


Ebay 69 https://cgi.ebay.com/ebaymotors/HOT-R...em280193942739


Next cheapest is for 85 a set.
https://www.hubcapmike.com/racing_disc_wheelcovers.html

Keep the weight as low as possible, since it takes more energy to accelerate and decelerate a wheel/tire that has more mass. This is a big deal for handling and in city traffic. At constant cruise speed, not such a big deal, but the ride will be harsher with a heavier wheel/tire.

Wheels may act as turbines, drawing air out of the wheel well and into the slipstream. This may be good or bad, aerodynamically: Good if it relieves air buildup under the car and thereby improves cooling flow, etc.. Bad if it buggers and aggravates the slipstream along the sides of the car. You are paying for every eddy, turbulence, and backflow caused by the movement of your car, all of which impact fuel economy.

On a wet highway, it's interesting to study the turbulence patterns of various vehicles, made visible by the mist and spray. A few years ago, a group of ~30 Porsche 944 guys did a ~500 mile all-day high speed ratrace through British Columbia, much of it on wet roads. The cars all had the same shape, but wheels and tires ran the gamut among Porsche styles. (Some wheels were fairly smooth disks, others had airfoil-shaped spokes to enhance brake cooling, most somewhere between.) You could see wide disparity among them, with some throwing spray well out from the car body, whereas others not.

Any hard figures on MPG increase from .cd improvements?

Hey got a friend I do some favors for that is going to buy me a set of speed disks / MoonEyes.

Loopie - are the

https://www.autoenhance.com/trimr.html

racing disks going to stay on the wheels ok ? Any idea how they compare to the MoonEyes like are they heavier or lighter??

The Mooneyes are spun aluminum clear powder coated and the Autoenhance at Stainless Steel.

It's a cool rainy day here in Newport but my Racing Disks came into Postall yesterday so when I venture out this morning I will go pick them up!

First issue is that the covers cover the valve stem - talk about aero extreem!
Not sure you easy it is going to be to pull them off - there are a LOT of little metal black painted fingers grabbing the rim and it looks like it fits right against the bead of the rim where wheel weights are mounted - should look pretty flush. I think I may give them a coat of tranlucent black to give them a black chrome finish since there is NO chrome on the xB and the polished stainless steel look doesn't quite look right.
Oh yeah just in time for my surprise trip to main in the next week or two - friend is coming in from Japan.

Hmmm.....I just got an idea. In another thread, someone mentioned that heat-shrink boat wrap is available in clear. If you put it on any random wheelcovers and shrink it tight and smooth, they would then be as good and might look okay, on the cheap.

Had a similar thought while looking for ideas in my place of employment. (WM)

Stumbled across a roll of self adhesive clear carpet protector. I could not get the stuff to go on smooth at all, and have no idea if my FE has increased, but the wheels quited down on a 1989 Cadillac Eldardo, and seems to be holding.

I put some duck tape on the lower portion of the front bumper and instead of going under the car the air goes right for the tires/wheels and I had a major increase in noise from the front wheels. Almost thought my transmission was going out on the first go. Talk about nerve recking.

Just the lowering of decipeles was well worth the ten dollars to me, and I have plenty of material to continue to play with. Like experimental tire skirts (yeah it will push in, but will keep the air out.) Covering a few of the crevices along the body of the car, etc. One thing I am interested in is how the material interact with long term exposer to the paint.

OM

Yeah I thought about using some clear stretch wrap using in shipping over my white "mag" plastic wheel covers but if they ripped loose at high speed it could take the cap with them. But it would keep the appearence of the mags that I like and keep them cleaner maybe - there was a lot of brake dust in the hubcaps when I pulled one off in front.

Well, so far so good, been about a week and a half and 160 miles over all with the covers and they have not torn away. With some rain driving also at 60-65 express way driving. To be truthful I'm surprised they have lasted as long as they have. As to plastic hub caps, no idea, I would be worried about the abhisive pulling off the finish. I know there is a warning about not using them on laminets.

I found these at JC Whitney. they are smoother than my old ones. even I will admit it was more for looks than FE on this one but they look good and they are on sale

https://www.jcwhitney.com/Wheel-Cover...3847_10101.jcw

and they come in different sizes

I almost bought a set that I suspect are aerodynamically similar (though aesthetically different) at WalMart for $15 but they are directional, and not mirrored -- so the slats point forward on one side of the car and backward on the other side. I decided that was not going to be so great.

Well put them on today and took a wet ride out to the Cape and back with 4 adults in the xB - hard to say if the mileage increased with the wheel covers or not but I got 41 average for the 142 mile trip in rain and headwinds going there and got some very good >50mpg coming back from Tiverton even pushing it hard when I took off which would usually lower my mileage to the mid 40's for that 19 mile trip. There may be a slight vibration from the covers as they may not be perfectly balanced but not so much that you would notice. Need more trips alone in good weather to see how much it improves mileage. They look great and have an excelent spun stainless steel finish.

Attachment 1351

Attachment 1352
Top view of left front wheel.

what did they run you? even if you don't get a huge increase, I think they look sweet. are they the pop on or screw on?

they make your ride look real smooth and clean.

Thanks to Loopie !!! - they are the

https://www.autoenhance.com/trimr.html

The stainless steel choice here in Newport is a good idea because of the salt spray that floats around in the air on foggy humid days. They just snap on and should just pop off with a good pull along the edge with some carefully placed fingers . . . I hope but I haven't tried to take them off yet. I hit the sidewalls with Armorall foaming tire cleaner and it also cleaned up the finger printes on the covers at the same time but as anyone knows with that stuff - a run in the rain washes it all off. Price was $69 plus shipping - not exactally sure because they were a GIFT!! YEAH !! The best kind of car accessory!

they are really nice looking. did you have to drill the hole for the valve stem?

I have seen them for $99 a set which I thought was a little high. I got some plastic caps which aren't completely smooth but they seem to do alright.

my wife has been looking for a gift for my birthday too. not sure what to tell her. she got on this web site and saw fender skirts. I am glad she talked to me about them because she was going to get me a set of mud flaps (that is what she thought fender skirts were).

as far as gifts go, I think those wheel covers was a good one.

OOPS - been working like crazy for the lasta few months - only added gas twice $25 each time since May25 but it looks like I get a couple more MPG with the racing disks. I do notice that coasting north on RT24 in Portsmouth down the hill that I pretty much maintain 50-55mph for most of the way now when before I would slow down about 5mph. Still haven't had a trip on the highway alone in good weather yet with the Racing Disks so until I get out to the Cape I will not know the highway impact but I am pretty sure it will be better that it was. One thing for sure they clean up a lot easier than the factory mag wheel covers.

They cover the valve stem since I had short stems on the rims - the stems do not extend past the lip of the rim.

Have to be a bit more careful with lighter tires. Since they're the same size, the weight has to come out somewhere. That means thinner sidewalls, fewer/thinner plies under the tread, less tread to touch the road, etc. Especially if you put 50 psi in them. Yikes.

Brian D.


When figuring your mileage with the 14" wheels did you make the necessary odometer corrections? If you went from a 13" wheel to a 14" your speedometer is going to be slow and the odometer is going to register less miles, so if the FE is checking the same you actually received some gain. You would just have to see how much difference the two tire sizes affected the odometer and figure FE from there.