Why does running one size bigger tires increase fuel economy?
I remember this from way back in the day, but I still dunno why this would help? Can anyone tell me? I know larry is running this so mehbe he'll chime in.
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i asked a similar question a
i asked a similar question a while back, relating to swapping to a "taller" transmission. the concept is the same.
https://www.gassavers.org/forum_topic/transmission_swapping_for_mpg.html if you put a taller tire on the car, it has the same effect: lower engine RPM for a given road speed = reduced losses to internal friction (engine, transaxle). you just have to make sure you have enough torque to compensate for the taller tranny/tire. (for most cars this won't be an issue; for my car it is an issue) when changing tire dia., you would also have to correct your speedo/odometer, or compensate manually when doing fuel consumption calculations. i tried to come up with a way of thinking about this that makes sense intuitively, and this is what i got: are there times you wish you had an additional (higher) gear (e.g. 6th)? if yes, then you could probably benefit from a taller tire/tranny. |
Hmm. Interesting, still a
Hmm. Interesting, still a little puzzling to me though, but I think I got it.
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you got me thinking about
you got me thinking about "losses due to internal friction", and wondering about just how large or small they are.
a quick, easy and illuminating data-gathering experiment for someone with an instant FE readout would be to record MPG at a constant speed (say 40 mph), on a consistent grade, in gears 2, 3, 4, & 5. would this not reveal the magnitude of losses from internal friction at various rpm for that car's engine & transmission? and then, wouldn't you be able to plot a curve and estimate changes in FE from further reducing rpm with taller tires/tranny? any takers? if not, i'll try to remember to do it next time i saddle up the blackfly (in a day or 3 probably). |
What'd I do to make you
What'd I do to make you think that? :p
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it would be cool to know the relative MPG for the other gears at that speed. |
So if my stock tire size is
So if my stock tire size is 195/65/15 and now I'm using 205/60/15, how big can I go to get a mpg boost??? My rim is 6 inches wide.
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https://www.miata.net/garage/tirecalc.html
I came back to this website and I figured the less revs per mile you have the less the tire spins. So my old 195/65/15 tire was better fuel economy if I were to pump it up. So... 195/65/15 Revs/mi:807 205/60/15 Revs/mi:817 -Current tire 205/65/15 Revs/mi:791 -Clear winner So would using 205/65/15 give me more of an advantage since it spins less per mile? |
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