Blocking of the back side of a rim - Fuel Economy, Hypermiling, EcoModding News and Forum

Floordford · 07-06-2011, 01:29 AM

I see many people doing pizza pan moon disks for the front of the rim. But has anyone done any attempts at trying to block off the back side of the rim? In my mind you couldnt really attach it to the rim itself but rather fix it to the suspension firmly and very close to the rim so it doesnt scrape. Im sure brake temps might be higher but not too many guys here are exercising their brakes enough for damaging heat levels to be considered. And im sure there would be a small gap to let some air into the rim. But i just think it would cut down on the rim turbulence in a big way if this could be done safely and effectively. It might even make the belly pans more effective.

cfg83 · 07-06-2011, 01:46 AM

Floordford -

I think we had a thread on this a few(?) months ago but don't know where it is.

CarloSW2

Joenavy85 · 07-07-2011, 10:41 AM

I don't see any advantage to blocking the back side of the rims. I would imagine that a belly pan that came close to the tires would do basically the same and would be easier to accomplish. As far as the front tires go, a set of wheel spats would minimize the airflow past the back side by deflecting it farther away from the tire. I can't imagine it would be worth the effort unless you have an open wheel car.

winkosmosis · 07-07-2011, 03:52 PM

How could that possibly help?

Floordford · 07-07-2011, 05:27 PM

Quote:

Originally Posted by winkosmosis

How could that possibly help?

The same as closing a window makes for smoother aerodynamics. The tire is disturbing the air and a plate to make the air path smoother would "help". People have been running covers on the outside of the rim for a while now. And a cover for the inside of the rim might help smooth the air under the vehicle so that it doesnt act like an open car window. I wasn't thinking of a ring to mount on the rim that would clear the brakes when the rim is taken off but more of a piece of aluminum that would attach to the suspension and be very close to the rim. Most cars with disk brakes already have a dust shield behind the brakes that is attached to the suspension. But I was thinking of something closer to the inside of the suspension that would make it to where the back side of the rim wouldnt effect the air going past.

skyking · 07-07-2011, 05:39 PM

I think with the space needed to accommodate the brake, you have entered the realm of diminishing returns. The air is already "dirty" under the car, even with a good belly pan.

mwebb · 07-08-2011, 12:30 AM

VW already has this
it is a real pain to see the rear pads from the inside because of it

Vekke · 07-08-2011, 02:41 AM

I have done that to my Seat rear wheels. Welded steel plates to suspension mounts. Cannot estimate the effect but it`s sure that i will help aero wise. No problems with brakes with smooth pizza pans + those. Every little bit helps

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https://skydrive.live.com/?cid=acb1f...!248&sc=photos

Floordford · 07-08-2011, 04:39 PM

Vekke, did you do any A-B-A kind of testing with them? I see you've done plenty of other mods.

aerohead · 07-08-2011, 04:46 PM

Quote:

Originally Posted by Floordford

I see many people doing pizza pan moon disks for the front of the rim. But has anyone done any attempts at trying to block off the back side of the rim? In my mind you couldnt really attach it to the rim itself but rather fix it to the suspension firmly and very close to the rim so it doesnt scrape. Im sure brake temps might be higher but not too many guys here are exercising their brakes enough for damaging heat levels to be considered. And im sure there would be a small gap to let some air into the rim. But i just think it would cut down on the rim turbulence in a big way if this could be done safely and effectively. It might even make the belly pans more effective.

Lakesters at Bonneville use them.Really, all the fast open wheel racers.
Danika Patrick has them on her Indycar ( carbon fiber,very nice!)
I have considered doing this on the trailer.They would have to be mounted on the axle,as they wouldn't make it past the hub if on the wheel itself.
I'll do the lower-hanging fruit first and then if time remains,I'll cobble something together.
Ford's inner fender,along with the urethane rubber wheel spat on the Probe-IV was good for a 9 % drag reduction.It's the only 'science' I have for such a mod,but it clearly demonstrates a drag reduction when the wheel is 'cleaned.' And this is a full bellypan car with only 3-inches ground clearance!
If anyone is seeking really low drag,then this sort of mod is certainly 'on the table.'