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Old 03-19-2018, 03:40 PM   #44 (permalink)
California98Civic
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Join Date: Mar 2011
Location: Coastal Southern California
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Black and Green - '98 Honda Civic DX Coupe
Team Honda
90 day: 66.42 mpg (US)

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Quote:
Originally Posted by CapriRacer View Post
Look at my webpage on the subject: ....
I did and so did some others, and thanks. This chart is interesting. It shows in general that wider tires are better but there are two cases on it that leave me wondering.



When I examine the individual data points, I see a couple things that interest me beyond the clear trend of wider tire = lower Crr.

1) The chart suggests that between two 75 profile 14" tires the 195mm width has lower Crr than the 215mm, yielding a Crr improvement from maybe 11.3 to maybe 10.4. Why is that? I'm not trying debunk anything. I am confident you know the explanation.

2) The chart also suggests that one might improve rolling resistance by reducing width from a 185/65-R14 tire to a 175/70-R13 tire--maybe reducing Crr from 12.0 to 11.5. Why?

Again, this is not an effort at debunking... just trying to understand why this happens so I can maybe make better guesses at good FE tire/rim combos in the future.
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See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.



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