OOPS - been working like crazy for the lasta few months - only added gas twice $25 each time since May25 but it looks like I get a couple more MPG with the racing disks. I do notice that coasting north on RT24 in Portsmouth down the hill that I pretty much maintain 50-55mph for most of the way now when before I would slow down about 5mph. Still haven't had a trip on the highway alone in good weather yet with the Racing Disks so until I get out to the Cape I will not know the highway impact but I am pretty sure it will be better that it was. One thing for sure they clean up a lot easier than the factory mag wheel covers.
They cover the valve stem since I had short stems on the rims - the stems do not extend past the lip of the rim.
metroMPG did a study on these and noticed only a few tenths (if I remember correctly) his site has a lot of good experiments that he has done and a lot of good advice too. from what I can tell, his experiments seem to be non-biased so I tend to put more trust in his results than others. he also tries to explain out why something did or didn't work.
it is a long read but you should check it out. metrompg.com
Be the change you wish to see in the world
A really simple test would be to jack up the rear wheel and spin the tire with a motor and let it coast down with various hubcaps on it or none at all and see what the difference is in spin time. Of course the weight difference would be a factor.
OK Guys I finally made the trip to Cape Cod on Tuesday this week . . . 44.1mpg going there typical highway speeds 88 miles average 51mph - then coming back there were headwinds so I took the old (lots of stop signs in certain areas) Route 6 all the way to North Darthmouth and when I returned to Newport RI . . . 49.0mpg!!
Seems the racing disks work pretty good at lower speeds.