Quote:
Originally Posted by F8L
During my testing I was using a set of lightweight 17" wheels (15lbs). One set of 15" tires weighed the same as the 17" tires so the entire combo weighed the same as the 17" combo so there was no net change in weight yet the mpg difference persisted much like it had with previous testing I had done in my GenII over the last 5 years. This along with other data like the OE 17" wheels (24 lbs) having and even lower impact on mpg leads me to believe that weight is not the prime force in determining mpg with wheels unless you do a lot of stop and go driving. 
I think the bigger factor is tire friction and hysteresis. |
Don't forget about angular force.
Larger wheels push more of the weight toward the outside of the package, which gives it more of a levered advantage, and takes more energy to start/stop.
On most combinations, the tire makes up at least half of the weight of the total package. Do you want that weight all in a very compact area?
The plus side to lower profile tires, however, is that you can generally move more quickly through curves - less slowing down and speeding back up.
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