Largest Tire Diameter on a 6th Gen Civic (for lower RPM)

[EcomilerChristopher]

So it seems people expect to get better mileage because your RPM's will be lower at higher speeds. However the larger the tire, the more energy is required to turn it, basic physics of inertia. So your car is going to be slugging away trying to turn that larger tire and hence worse fuel mileage.

[tasdrouille]

Originally Posted by EcomilerChristopher

So it seems people expect to get better mileage because your RPM's will be lower at higher speeds. However the larger the tire, the more energy is required to turn it, basic physics of inertia. So your car is going to be slugging away trying to turn that larger tire and hence worse fuel mileage.

Since you mentionned inertia, I'll take it that you meant it takes more energy to accelerate it. Remember that once you've spent energy accelerating the tire up to speed, that is stored energy you can use later on. Once the tire is up to speed, mass has little impact and RR dictates the energy required to keep it rolling, so it will not be much different then the smaller tire.

If larger tires lead to worse fuel economy, it's mainly from the driver's inhability to properly use that stored energy in any given situation.