Tires: 185/65 or 195/65???

[theholycow]

That article is about upsized wheels and shorter sidewalls, not about tread width. There is some variation in tread width but the test is nowhere near good enough to prove or disprove the hypothesis that wider = less RR.

Edit: In fact, the largest difference in fuel economy in those tests was between two tires with the same width.

[Sludgy]

Originally Posted by theholycow

That article is about upsized wheels and shorter sidewalls, not about tread width. There is some variation in tread width but the test is nowhere near good enough to prove or disprove the hypothesis that wider = less RR.

Edit: In fact, the largest difference in fuel economy in those tests was between two tires with the same width.

The difference in width was 235 vs 195 mm top to bottom. 40 mm is approximately a 1.6" of width. I think that's significant.

The mileage difference between widest and narrowest tires was also significant; 21.1 mpg for 235 tires and 23.3 for skinny 195's.

[theholycow]

Right, but considering that the same width tires have equal or larger difference in MPG just for upsized wheels, obviously upsizing the wheel has a big effect. We can't gather useful data for width from that article.