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Old 04-19-2020, 12:20 PM   #1 (permalink)
Aero Wannabe
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Join Date: Dec 2007
Location: NW Colo
Posts: 686

TDi - '04 VW Golf
90 day: 47.98 mpg (US)
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Heresy! Smooth Wheel Covers- Myth Busted!!!

At least on the VW Golf

I have tried various forms of wheel covers for over 10 years on my diesel Golf 5 speed manual with no real improvement in highly mpg. I have had several entire tanks testing them where the mpg seems to go down. Wheel covers are one of the first mods many people try on this forum. There is a historical tradition of using Moon wheel covers on salt flats race cars and intuitively they “look” like they would work much better than the blender blade mess of most alloy rims. I recently purchased Julian Edgar’s book and he quotes several studies of airflow and drag on car wheels. These studies show that totally smooth wheel covers are not the lowest drag option in modern automobiles. This would fit with my personal experience and motivated me to do some further testing in an A-B-A or even A-B-A-C-D options. I will post my test data and observations in a following post.

60 mpg hwy highest, 50+mpg lifetime
TDi=fast frugal fun

Originally Posted by freebeard View Post
The power needed to push an object through a fluid increases as the cube of the velocity. Mechanical friction increases as the square, so increasing speed requires progressively more power.

Last edited by COcyclist; 01-09-2021 at 08:12 PM..
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