Car question: Do larger wheels get better fuel economy?
by 
Jason Cutler
ANSWERS: 3
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even if they do, the amount would be so small, its not measurable. well thts what in think anyway. my logic is a bigger wheel is heavier so it would make the MPG worse.
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All else being equal, bigger tires mean WORSE MPG. If you are running tires of the same rolling diameter and merely running larger rims and lower profile tires then your MPG may change slightly (usually for the worse) depending on the mass of the wheel and how close that mass is to the center of the rim (rotational inertia).
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If the diameter of the wheel+tire package is made larger, it effectively raises the final drive ratio (more distance traveled per engine revolution), which *might* produce slightly better fuel economy. Changes in speedometer accuracy and throttle opening needed to maintain speed make this uncertain. OTOH, if you increase the wheel diameter but decrease tire height (smaller aspect ratio) to keep overall wheel+tire diameter constant, then you will get slightly *worse* fuel economy. The bigger wheel/shorter tire combination concentrates more weight at the periphery of the wheel/tire and a larger wheel puts it further from the center for rotation. Both of these increase the moments of inertia (rotational analog of mass) of the wheels. Hence, it takes more torque to get them moving. For reasonable changes in wheel/tire setups, the effect is probably quite small (on the order of 5%)
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