//// Tire / Wheel aerodynamics /////
 

Hi All,

I know many people try to increase wheel aerodynamics by installing Pizza Pans onto their wheels (I did too but when I switched to aluminum wheels to save weight I lost my easy ability to attach the pans to the wheels ( for the steel wheels I screwed the pizza pans onto hubcaps and then pushed the hubcap assembly onto the wheels .... yes, the pans rode out a little but I figured something is better than nothing and it was an easy attachment method .... unfortunately I could not see a MPG increase when I did that... maybe because the pans mounted to the hub caps stuck out too far from the actual wheel and caused turbulence ?

Anyways, in looking closer at my new rims and tires (factory VW Avus rims with 205 75 R15 Ecopia 422 Plus tires, even if I flush mounted the pans to the wheels themselves, I saw that tires overhang the flush mounted pizza pans ...

I am assuming unless I went with wide rims, the face of the pizza pan equipped wheels the would most likely never match the sidewall of the tire therefore causing a place for turbulence to start (I hope you can understand what I am saying without pics)...

I think a solution for that would be to get rubber or heavy nylon (water resistant rot resistant) in the form of a disk than can be glued to the sidewall of the tire near the point of maximum "bulge" .... THEN viewed from the tread area looking back , the outer "face" of the tire will be flat with no "pocket" where the typically recessed wheel would be .... I believe THIS would give a tire MAX aero.

NOTE that the cover has to be taut yet somewhat flexible when glued to the sidewall since a tire will flex when driven but it has to be tight enough to not excessively flutter i the wind so as not to disturb aero.

To make tire pressure checks possible and access to the lugnuts possible I thought about maybe fastening with velcro or if gluing simply haveremovable access panels.

I suppose ideally, the wheel would have to be sealed so water can't splash into the glued covered area (from the back side of the wheel) so dirt doesn't build up and cause potential abrasion where the glued on fabric or rubber disc meets the sidewall.

I hope you can envision what I am saying without pics.

What so you think of this idea in terms of better wheel / tire aero ?

Thanks in advance for any and all input.

Andrew

tire sidewall bulge
 

The camber of the sidewall is gentle enough that the air will remain attached, to and from the wheel cover. I wouldn't sweat it. Just killing off the major portion of wheel 'ventilation' is enough to provide the streamlining.

I would not attempt to attach anything to the sidewall of a tire, not even the proposed flexible membrane/diaphragm.

Safety comes first.

Messing with complex wheel dynamics is an unnecessary legal liability in my opinion- but I'm not a lawyer.

Flow through the wheels
 

The other thing to think about is if there is flow through the wheels, many front engine cars exhaust cooling air through the wheels and arch area. Blocking that flow can cause and increase in drag or lift.

This is the best solution I've seen. The wheel disk overlaps the tire sidewall. This is regarded negatively, but it suspect next to the bead the sidewall doesn't flex much and the wheel disk is probably as flexible as the tire.

https://i.imgur.com/Cdh4U9B.jpg

On my Notchback Type III, I ran 145s on 5½" rims, drifter kids these days run rims wider than the tread.

Drifter kids do stupid things to tires. What does capri racer say about drifting?

Hi

Yes, this is exactly what I was thinking of in terms of coverage ( except I was not intending to do the inside the car side if the wheel).

Also, since my vehicle will be Street driven I was going to use something more flexible as a cover and most likely attracted to the sidewall utilizing some sort of adhesive..


The reason I thought of the adhesive was to keep friction and abrasion down between the sidewall and the cover piece if they were made separately and not attached together (i.e. the two pieces would rub if they were separate but touching and not moving uniformly thus causing abrasion wear / damage).

Thanks for the picture.

Andrew

It's one of my favorites too.

I'm skeptical of the the 'wear and abrasion' claim. It seems like the tire would have to be spinning on the rim to wear. In any case the overhanging lip could be coated with Teflon if it's that big a problem.

Hi

What I meant was if I glued a rubber disc to the sidewall of the tire, I would be worried if debris were to come in from behind the wheel (through the wheel spokes) and eventually work it's way into the gap where the glued rubber disc met the sidewall causing abrasion as it flexed...

Admittedly I don't go driving through beaches and off-roading so maybe dirt and debris would be minimal.

With the case of a solid disc touching the sidewall of the tire since the sidewall could Flex under heavy cornering I would worry a little bit about a non movable disc causing issue with the sidewall..

It's almost like running a dually Tire setup you don't want to rock with something to Lodge between the side walls because it couldn't damaged sidewalls...

Duallys on pickup truck or big truck usually have a gap between the Dual Tires to keep sidewalks from rubbing and or getting something lodged between them easily and wearing out the sidewall...

Maybe I was being overly paranoid but I really didn't want to have a blow out ecomodding. ;-)

Portawalls. Consider Portawalls.

https://i.ebayimg.com/images/g/yFoAA...ObA/s-l300.jpg
https://i.ebayimg.com/images/g/yFoAA...ObA/s-l300.jpg

They are trapped between the tire and rim, instead of being bolted to the face of the rim. One could fasten them directly to Moon disks.

They travel in 'close accordance' with the wheel and tire.

Tell me about it, in the 1980s I was driving my 1957 Beetle through the Thurston Hills (where BLM roams now that they've been kicked out of Portland) following a dump truck. It threw a rock the size of my fist right at the hood, in front of the steering wheel. But because the Beetle's hood is rounded it bounced sideways and tore the rear view mirror right off the car!