anyone know the benifits of lightweight wheels?

[fu_im_from_texas]

Originally Posted by CaysE

...fu, the weights of the wheels themselves could've told you the same thing without going through all that calculation. 10 lb wheels are 33% lighter than 15lb wheels, thus requiring 33% less energy to move them....

CaysE, You are right!...This is only true for the simplest case, which I examined here. If we concidered the case of 17inch 10lb rims, then the moment of inerti would be larger...the moment of inerta grows exponentialy with the radius of the rim.

Originally Posted by CaysE

Cliffs notes: you're only looking at half the picture.

Can you please provide a calculation for the other half of the picture?

Originally Posted by Biggie™

...You are comparing the amount of energy while driving at 60 mph, not the amount of energy it took to actually accelerate the extra 20 pounds of wheels...

Biggie, This is false. When the car is going 0mph the energy is 0. When the car is going 60mph the energy is about 4xxx kW. The difference, or amount of energy it takes to accellerate the mass is 4xxx-0 = 4xxx kW

Originally Posted by Biggie™

...
Also you didn't factor the rotational weight effects. You just treated the wheels as a non independent part of a mass that is the car....

The first portion of my calculation was the rotational effects...

One error I do see is I compaired the energy of 1 wheel, when there are 4 on a car....multipling the energy of 1 wheel x 4 still nets a neglegable ammount of energy...

Can anyone provide an alternate calculation?

[Biggie™]

Originally Posted by fu_im_from_texas

Biggie, This is false. When the car is going 0mph the energy is 0. When the car is going 60mph the energy is about 4xxx kW. The difference, or amount of energy it takes to accellerate the mass is 4xxx-0 = 4xxx kW

Wrong again buddy... In your equitation you are attempting to calculate the actual energy the Yaris possesses at 60 mph. Not the energy it took to get the car to 60mph. But thank you for letting us know what the ballistic energy of an object that is close to the mass of yaris being flung out at 60 mph.

What you need to do is calculate "force", mass multiplied by acceleration. And of course it will take less energy to accelerate a lighter object. The formula to calculate rotational acceleration is a bit more complex, but this is actually what you are looking for here. Try google...

[fu_im_from_texas]

Originally Posted by Biggie™

...What you need to do is calculate "force", mass multiplied...

Biggie,
I am approaching the problem from an energy stand point. I base this approach on the first law of thermodynamics - a law that states there is a conservation of energy.

You are approching the problem from the standpoint of Force. You are useing Newtons second law of motion. F=ma...

Both are valid. There is 300+ years of emperical evidence that shows that conservation of energy, and F=ma will ultimately get you to the same answer. I am using conservation of energy because, in this case, it is the simpler approach...

Originally Posted by Biggie™

... Try google...

I have a degree in mechanical engineering from the university of texas @ austin. I have taken several classes in physics, dynamics, and dynamic system controlls. My approach to the problem is correct. Google will give you a ton of information. Information is dangerous when it is applied incorrectly...

I am not trying to give you a hard time here, because we are all trying to figure out the same answer to the same tough problem ...