Quote:
Originally Posted by Big Dave
Your drive train doesn’t accelerate the vehicle away from a light. It accelerates the wheels/tires. The tires grip the road and that equal and opposite reaction thing accelerates the vehicle. You have to pour kinetic energy into the wheels before they move your vehicle.
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This is a flawed assumption. You have arbitrarily chosen a drive train component as a store of kinetic energy. Why didn't you specify the drive shaft? Why didn't you specify the 2nd gear in the transmission? Because it would be just as arbitrary.
Tire size vs. acceleration has far more to do with moment arm mechanical advantage than kinetic energy or moment of inertia of the tire/wheel. A smaller tire gives greater mechanical advantage to the engine, so for a given amount of power, you get a greater force at the contact patch and therefore greater acceleration. This is exactly the concept of drive ratios and transmissions.
Small fuel efficient cars have small tires because they are small cars. They need to be light, so they use small tires/wheels because they are lighter than big ones, and it would frankly look silly otherwise. They are also geared for optimal efficiencies for different operating speeds. My HCH2 has 195/65-15 tires on it, and it has light wheels that have minimal styling cut-outs for reduced aero drag of the wheels.
Yeah, but it's a hybrid, right? Sure, but at 60-65mph at steady state, the hybrid system is nothing more than added weight and a means of keeping the 12V battery charged. It's simply a highly efficient and optimized 1.3L 4 banger running in lean burn mode getting 50+ mpg. It was optimized for this operating condition and tire diameter. If I alter that, I'm probably going to see a decrease in efficiency either way. Of course all this assumes that I can control enough variables to make any experimental results meaningful.
I apologize if I sound dickish. I don't mean it to be that way.