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Old 04-12-2009, 04:10 PM   #8 (permalink)
cfg83
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Join Date: Dec 2007
Location: Southern California
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1999 Saturn SW2 - '99 Saturn SW2 Wagon
Team Saturn
90 day: 40.49 mpg (US)
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younggun -

Here is my thread on the same type of upgrade :

http://ecomodder.com/forum/showthrea...ires-2642.html

I used tire size change calculators on the Internet to predict what would happen. Also, tirerack.com shows the "revs per mile", which is another predictor of how much you will lower your RPM. Then I used a GPS to verify the error in my odometer. I didn't bother to recalibrate my odometer or speedometer. I already have a Scangauge, so I can apply the correction there and see my "real" MPH in real time if I want. I just apply the correction to my fuel log, so it's like a mini-bonus.

And yes, as others have stated, the tire tread is important.

CarloSW2
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