The equation that is used is circumfrence=2?r. Its basic geometry, I am guessing you aren't working in the engineering department of superlift, if so Im scared. A larger wheel of any kind is going to wear less than a smaller wheel because it rotates less than the smaller wheel will. It has absolutely nothing to do with weight. You need to put things in perspective, you are comparing two tires that are of similar size. To get a better idea compare two things of extremely unequal size but made of similar properties. Now think of inertia and momentum, logically you would think that a larger heavier object would slow faster than a smaller light weight object. Not so in most cases, compare a marble to a boulder, say I roll it down a 15 incline that is 100yds long and then goes to a zero incline thats an infinite distance. Which object is going to roll further? As I stated and another member stated, once in motion objects do not stop unless other forces act on them: friction, gravity, etc. So once you get those big wheels turning it doesn't burn any more fuel to keep the larger wheels rolling than it takes to keep the smaller wheels rolling. Its called conservation of momentum, its part of newtons first law. What takes the most amount of energy is always used to get the initial momentum going, after that sustaining your momentum is not a problem. If you really wanted to get technical you could factor in everything that could possibly prevent you from getting better gas mileage but it would still show that the larger tires will net you better mileage on the HIGHWAY as I stated before. There is always a trade off, its like hybrid cars, they get better gas mileage in the city when its stop and go driving and worse on the highway, but they get better gas mileage all around. Simply put as I stated before tires act the same way that changing gears do, if you want to do a comparison go to www.4lo.com
and they conversion tables. I wouldn't base my argument on that of the EPA or auto manufacturers, larger tires cost more money to make, more money equals less profit. It may not seem like much but there are plenty of things that auto makers can do to make there vehicles get better gas mileage, but its a tradeoff, newer technology costs more money, if manufacturers spent another $100 on every car they make to conserve fuel they would be losing 100X # of cars sold every year. When you sell 20 million cars a year thats an extra 2 billion dollars a year more to save the consumer an extra 2 gallons of gas per mile. Its not good business for them to do that. Auto makers and government bodies are influenced by money, so dont rely on that to make an argument. You should have more respect for other members especially when your talking out of your ****.