thx for the input.. got me thinking. I went to the DML homepage and used the
calculator and the diff in 235/70/15 and 255/55/17 is like 0.09 or
something. Not a big enough diff to tell. Guess my speedo is off from when I
put on the white face gauges.
Oh well, thx for the insiteful input ( I don't really know metric) hehe
X---------------------CrawdaddY--------------------------------------X
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New Orleans, La
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see above profile for more info on my Dak =]
X--------------------------------------------------------------------X
----- Original Message -----
From: "Patrick and Kelly Engram" <patrickandkelly@erols.com>
To: "DML" <dakota-truck@buffnet.net>
Sent: Wednesday, March 28, 2001 10:09 PM
Subject: DML: changed to R/T size tires, now fuel mileage dropped?
> "might sound weird, but when I went from 255/60/15 to 255/55/17 RT rims
> and
> tires, I noticed that I can't go over 20mpg on my overhead anymore. I
> used to get 21 doing 60mph or less on the hiway, I can barely get 19.5.
> This
> could be due to the difference in tire size has thrown off the
> calculations,
> but I think the RT has the same overall diameter as the stock tires,
> 255/65 (mine were 255/60)
> Dunno, could be wrong. I am sure there are others than can answer."
>
> -Interesting thing to note. The stock 255/60R15's should have an
> overall diameter of approximately
> 687mm. The R/T size 255/55R17 stands about 712.3 mm tall, roughly 2 1/2
> cm., or almost exactly 1 inch
> taller. Who's the math wizz on the list? If you have a taller tire
> that at the same rate of revolution as the smaller
> size, will travel further in distance due to an increased
> circumference. The fuel mileage on the computer
> would read lower, but the distance traveled would be further than what
> the computer thinks, due to it taking
> its reading off the speed sensor on the transmission.
> So, is the gas mileage affected? Only if the replacement tire is
> shorter in diameter, not taller in diameter. Being shorter will raise
> the engine rpm at any given speed, increasing fuel consumption.
> Patrick
>
>
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