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Old 06-19-2013, 11:04 AM   #16 (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)

Black and Red - '00 Nashbar Custom built eBike
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Quote:
Originally Posted by Fat Charlie View Post
I can see low pressure with a car sitting on top of it, allowing deformation and reduced diameter. Higher pressures really shouldn't stretch the steel belts past nominal size. I'd think higher pressures would increase resistance to deformation (=LRR) without an actual increase in diameter.

This doesn't account for people like Ford specifying really low pressures in their Firestones for a cushy ride, but if reasonable people set the spec, going to max sidewall or beyond shouldn't affect size.
This makes sense, but I think Pale still has a point. If the OEM psi spec is low enough to allow deformation under the car's weight (which it does of course) then higher pressure might help the tire keep more of its max design diameter. If the car makers factor the deformation into their expectations for the odometer/speedometer, then wouldn't higher pressure produce fewer revs per mile? What am I misunderstanding?
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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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