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Gearing
bigger 4 wheel drive trucks pick their tires first. then use the gearing they need to get the rpm of the engine where they want. what i was wanting to know why use 155/80/13 instead of 145/82/12 tires with even taller gears.
remember in all examples we want the engine to be turning at the same rpm versus mph, (for example 2000 rpm at 55 mph)
This is the deal, the 12 inch car turning 2000 rpm at 55 mph, would set lower to the ground, weight less, reciporcating mass would be less, tire width less.
the 13 inch car turning 2000 rpm at 55 mph would be higher and weight more. is it only because nobody makes gears? some of these guys go to extra ordinary lengths for just a very little economy. this seems to be alot bigger payoff and nothing.
a way to maybe test this would be get a car with the 12's in fifth gear and compare it to 13's in fourth, once we fiddle with making the rpms the same at 55 for both tires, we could see the payoff in fuel economy for the smaller tire. This would justify even a special order gear for a tranny. We are doing alot more for alot less
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