Tires: Load Range E tires on an Explorer???, heavy duty trucks, gas consumption

Question
I'm seriously considering upgrading from a tire size of 255/75/R16 factory reccomended tire to a 245/75/R16 "Load Range E" tire.
My  question is this: What will the noticeable difference be in driving, handling, and gas consumption?
ALSO, what do the 3 groups of numbers signify? (I.E. 245/75/R16)
PLEASE HELP! I'm clueless...

Answer
Matthew,

Yes, there will be a decided loss in fuel economy.  How much depends on which tire you choose.

The vehicle will also ride rougher, and handle more like a truck.

I suggest you stay with tires with the letter "P" in front of the size.  These are designed for your application - an SUV - where the tires with the letters "LT" (or use Load Ranges) are designed for heavy duty trucks.