Quote:
Originally Posted by MetroMPG
... However, aside from the tire width / RR changes, we don't know what other changes they made that might affect rolling efficiency
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Absolutely. But it is a reasonably safe assumption that they would not be using narrower tires if they knew it would undermine any further changes they were making to improve rolling resistance and range. Especially in the era of wide and low profile tire popularity.
This is a great discussion thread in general, too.
When I bought the MINI seven hole 15" wheels recently, it was partly because it had 175/65 tires. That is the same width as the tires on my 13" VX wheels. The new wheels are just 12 pounds to the old ones 9.7 lbs.
In sum, same width, much taller gearing modest but significant weight penalty.
I learned all of that on EM (sure hope it is true, haha!).