The eVOLVE Hybrid Wheel made of metal and plastic, designed for the 2012 MYFord Focus SE, has shown an increase of 1.1 MPG highway in third-party tests, compared to the car's standard production wheel. (Source: Lacks Wheel Trim Systems)
Our testing shows that completely covering the wheel achieves better aerodynamics, that said cooling and design is compromised so it is not a realistic option. Wheels are as emotional as they are functional – especially considering the side on visual impact of the vehicle. The eVOLVE hybrid wheel philosophy is to balance, weight, aerodynamics, design and finishes all at the same time. We believe composite wheel technology provides the ultimate method to balance all attributes as best possible.
Thanks to Lacks (James, I believe that's you commenting here) for weighing in on the testing issues, as well as giving us more info on the design tradeoffs between aerodynamics, cooling and esthetics issues.
Thank you Ann for inviting us to provide additional information here. There have been some excellent and insightful comments made by the readers and clarification is always good for both parties. If further information is required, your readers can visit us at www.evolvehybrid.com or stop by booth 325 at the upcoming SAE World Congress in Detroit, April 16-18 for a first hand look at the eVOLVE hybrid wheel.
The Citroen SM, introduced in 1972 had composite wheels as an option, but they really didn't catch on. Citroen was also known for its low drag aerodynamic designs tested in its wind tunnel that had a moving conveyor belt, as they maintained that the interface between the car bottom and the road had the greatest wind shear and hence presented the greatest drag. All Citroens, including the ugly 2CV had very smooth bellies.
If weight is important in the wheel tire assembly, then perhaps tire weight deserves another look. I've noticed incredible weight differences between different tires of the same size. I've also noticed that the heavier tires really bounce when dropped. Unsprung weight has significant effects on handling on uneven surfaces as well as ride.
The latest fashion for low profile tires reduces the amount of rubber and air cushion and increase the amount of rim.
Speaking of aerodynamics, both the Citroen SM and the (1954 - 1972) DS featured full and smooth wheel covers. Brake cooling was by separate ducts to inboard transaxle mounted disc brakes. Brake fade was unmeasrable. Interestingly, with front wheel drive, the very reliable CV drive shafts took the full force of braking - much higher than engine output. These FWD transaxles and components were a favorite of formula 1 cars for many years when used in the rear.
I find the engineering of Citroen awe inspiring because they certainly marched to a different drummer well ahead of the mob. The Citroen DS, which has more leg and head room than my 4050 lb Buick Lucerne weighed in at an amazing 2700 lbs. The current Fiat 500 weighs in at 2600 lbs. With its self adjusting air/hydraulic suspension, the DS rode perfectly under all loads, superior to my 2007 Lucerne CXS's magnetic ride.
cookiejar, I had a similar thought when researching this article--how incredibly complex the process is of analyzing all the variables and how they interact. Thanks for the input on the Citroen wheels. Interesting to know that such design considerations--aerodynamics and materials--were being looked at back then. I wonder if that's the Citroen model my husband and I rented in France in 1974.
Most of the new 3D printers and 3D printing technologies in this crop are breaking some boundaries, whether it's build volume-per-dollar ratios, multimaterials printing techniques, or new materials types.
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