Quote:
Originally Posted by mpg_numbers_guy
How are you calculating your multipliers? I would think it would be just as simple as new tire circumference divided by old tire circumference. ...
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I know it would seem that way, but my odometer and speedometer are like a weird black box. I have learned to use GPS and Google Maps to calibrate distance with every tire and or wheel change. This time rotating tires meant a different brand got onto the front wheels, so...
I can't remember the exact numbers (I have screenshots on anotuer device) but on my trip to El Mirage I drove what the GPS called 86.55 miles to a known point on the route. Google called it 86.6 and my odo recorded 81.xx or something. That is a big undercount, but smaller than the other tires that just were moved to the back two weeks ago... same size. The tire companies reporting cannot be strictly trusted, and I want precision, as much as I can reasonably get. So I measure each time. My odometer is maybe 7.25% undercount but the speedo is only a little under (I think the speedo dial is slightly rotated from the factory).