Owner operators and truck fleets may use aerodynamic wheel covers to help reduce air resistance and improve fuel efficiency for their trucks.
They are one of a number of truck operations enhancements.
We must state that since our professional truck driving experience has only ever been as company drivers with companies who did not use this technology, we have no direct experience with these devices.
However, because of the return on investment that you will read about below, we expect that they will become increasingly popular.
As you can see in this photo of the drive axles on a tractor operated by Schneider National, one wheel has a cover while the other does not.
Examine the smooth appearance of the covered rim versus the uncovered wheel and the bowl-like "indentation" of the uncovered rim.
This is a close-up of the device on a Schneider National truck.
It was manufactured by Deflecktor (Deflecktor.com).
According to their website:(1)
By streamlining existing contours of trucks and trailers aerodynamic benefits become fuel savings for virtually all highway applications. Fuel savings from improved aerodynamic efficiency occur most dramatically with increasing road speed. In SAE type 2 J1321 fuel efficiency tests the DEFLECKTOR Aero Wheel Cover was found to save 1/4 of 1% per cover. A tractor trailer can expect an increase of 2% when installing the covers on all eight wheel ends.
When it comes to the contours of truck tire rims, what are we talking about here?
This photo shows a typical tire rim of a large truck, with all of its contours, from the front or outside in a vertical view.
This hand-drawn illustration serves to show -- with the wheel rim oriented horizontally -- the approximate contours of
- the tire rim shown above and
- a stream of air running past it.
Actually, this illustration does not capture the way air swirls and tumbles like this next image shows...
Swirl and Tumble
This illustration of a swirl and tumble shows what air does when it flows in certain situations.
From this illustration, you can certainly tell how the vertical areas of tire rims could lead to air resistance.
Reducing air resistance is key to saving fuel.
In this photo, both drive axle tires are covered and appear smooth.
The air can flow right over them.
Here's another truck with Deflecktor devices on the drive axles.
How much of a difference does using a product like this make on fuel usage?
Here's how the savings calculator on the Deflecktor.com website figures your potential savings (based on our input):
As with most add-ons, there is an upfront cost.
As of the time this page was first written, these units cost US$50 each (even with a logo).
However, as you can tell, there is return on investment.
Naturally, good news about fuel savings in the trucking industry has to be told....
Schneider News (March 23, 2010)
(http://www.schneider.com/news/News/PRD_003438 - no longer online)
Link 2 - TruckingInfo.com (March 24, 2009)
Link 3 - LogisticsWeek.com (March 2009)
Schneider News (April 19, 2010)
(http://www.schneider.com/news/News/PRD_003506 - no longer online)
(http://logisticsweek.com/road/2010/03/schneider-national-outfits-tractor-fleet-with-aerodynamic-wheel-covers/ - no longer online)
Even with all of this information, Vicki still had questions.
So, on 11/26/2010, she submitted an email through the Deflecktor.com website.
To save room and redundancy, we will publish the response she received within 1/2 hour (Wow! What turnaround time! And on the day after Thanksgiving, at that!) that includes her original email.
This reply came from Jonathan Fleck at Deflecktor, who has given us permission to publish it on our site:
Here is my best stab at answering your questions. Please check out Schneider's press release from April of 2010 where they report a 150 gallon savings per truck per year. They report 1.8 million gallons saved over their 12,000 truck fleet annually. That is at average road speeds in real world, their average road speed is something like 48 MPH.
Hope this helps. My cell phone is [removed number for privacy reasons] if you have further questions.
Hoping this E finds you and yours HAPPY and HEALTHY!
I am Vicki Simons of Truck-Drivers-Money-Saving-
1. One page of your site: http://www.deflecktor.com/Category/Wheel-Covers.cfm states, "A tractor trailer can expect an increase of 2% when installing the covers on all eight wheel ends." While I have seen wheel covers on drive axle wheels, I don't recall seeing them on trailer axle wheels. Do you have any documentation to show the increase in fuel efficiency for putting wheel covers on trailer axles wheels? Is the efficiency better, worse than or the same as drive axle wheels?
Schneider has the documentation - the DEFLECKTOR is the most tested accessory ever tested by Schneider. The entire test document has been submitted to EPA. Schneider runs 4 trailers to each tractor that is largely why the investment is much quicker on tractor vs trailer. In fact it is the quickest ROI of any aero device going right now. Schneider is equipping their trucks because of ROI not for any other purpose, regulatory or otherwise.
2. What is the life expectancy of you wheel covers, such as one year, two years, five years, etc.? (This will factor into replacement costs.)
We have wheel covers with 1,000,000 miles on them.
3. Is the fuel efficiency enhancement of your wheel covers affected by road dirt, road salt (especially in the winter), snow, ice or anything else?
Not really - however it is critical that the unlike atmospheres be completely separated - therefore holes of any sort on the wheel covers face impact turbulence. You see air spilling out of the wheel and the air rushing past the wheel cannot meet as this is the point of turbulence - much like a window opened - or even slightly cracked. It is critical that there be complete coverage. It has only been recently that knowledge in this area through computational fluid dynamics (CFD) has been realized.
Does a driver need to be concerned about cleaning the wheel covers regularly?
No - the covers spin at approximately 500 rpm - the face largely stays clean as a result.
If so, with what should they be cleaned and how often?
4. My husband Mike says that he has noted that Mesilla Valley Transportation (based out of Las Cruces, NM) uses metal wheel covers on their tractor drive axles. From what we have been able to determine, it does not appear that your wheel covers are metal. What documentation might you have to show the superiority of one type of wheel cover material over another?
Our covers are fabric - they do not require a single tool ever - please watch our install video to more completely understand the advantages. MVT is a customer, as is Daimler, Volvo as well as many other major players in truck transport. The covers weigh 800 grams - much lighter than metal, they do not dent, corrode and are inexpensive.
Perhaps the weight of the wheel cover material -- or its shape -- has an influence in fuel efficiency enhancement?
Shape is not as important as complete coverage. No holes is paramount.
Thank you in advance for answering my questions. I greatly look forward to hearing from you. Please answer by email at your earliest convenience.
Money saving tip: By removing areas of air resistance on big trucks, fuel efficiency can be increased.
Wheel covers can improve truck aerodynamics, reducing air resistance and increasing fuel savings.
We strongly recommend working to find and reduce (preferably eliminate) areas of air resistance on your truck.
If you try these products or something similar, let us know how they worked for you.