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big dave said......As for bigger tires, I can give you one piece of advice: If you increase tire diameter, your MPG will DECREASE. Repeat DECREASE. This seems counter-intuitive but it is borne out by empirical data reported by literally hundreds of people.
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Three things cause MPG to go down as tire diameter increases.
First is that the rotational moment of inertia increases with the square of the diameter. This means you have four bigger “flywheels” you have to spin up everytime you pull away from a stop. If you were an over-the-road trucker – a creature of the superslab – this would not be very important. They get up to speed and keep rolling at the same speed for hours on end. I daresay you don’t drive that way. You do some stop-and-go. Big wheels stick it to you at every light.
Secondly rolling resistance seems to go up with tire diameter. I am screwed with my 16 inch wheels. The highest MPG cars tend to have clown-car tiny tires. Rolling resistance matters a lot at slow speeds.
Old men have very little hair on their head.
Old men get haircuts that take all the hair off.
The highest mpg cars have clown tires.........so what? THey have little engines....ergo you can't get good mileage with a big engine?????????
So go jump off a bridge????????
is that the rotational moment of inertia increases with the square of the diameter.
I really believe that WEIGHT just might play into this equation????
Fact: 255/45/18 is a larger diameter than 245/45/18. Weight is identical. I get better mpg (documented)
You tend to be in love (and thus blinded) by this idea that 'larger tire BAD'. It just is not true. It's like saying wiskey is bad. no, TOO much wiskey is bad.
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