Quote:
Originally Posted by TurnOnTrance
I have downsized my tires to a 195/50R15 and I have achieved much better combined MPG. If off set my speedometer a bit and i have calculated that my odometer will be off by 10% but even still I have been achieving around 42 MPG Combined Driving (thats city and highway). My highway MPG has dropped form 47 to about 44ish (depending on how badly i decide to speed). But my complete city driving MPG has gone up from 34 to around 38. I also run my tires at 38PSI cold pressure and i also have eibach sportline springs with Koni shocks. Oh i currently run Bridgestone Potenza G009. The next thing i am going to try is going back to a 16" rim but a much lighter one with a 40 series tire on it, because if you lighten up the rim and have a low profile tire on it, it should decrease the overall weight of the rim and tire combination which should help lessen the power loss due to a heavier wheel and tire and up the mileage. Let me know how you make out, and if you get the same results.
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Your speedometer and odometer are only off 3.2%, not 10%. What happens when you subtract 3% of the mileage distance before you divide by gallons used?
And if the low profile tire weighs more than your current tire going to a lighter wheel won't overcome the energy it takes to rotate the heavier tire.