Put a set of 'holey' 15's with snow tires on today, and the difference in acceleration is incredible. I think they're about 18lbs per corner ligher than the 17's with the runflats, but it seems like a lot more than that.

http://www.flickr.com/photos/jabella/6496245237/http://www.flickr.com/photos/jabella/6496245237/ by http://www.flickr.com/people/jabella/, on Flickr

I'm tempted to just get summer tires for the 15's in the spring, or find some light 16's....

 

There are doubtless folks with far more automotive knowledge than I who can better answer your questions, but from my years riding road bikes (including momentary bouts as a weight weenie), I can tell you that all weight is not equal. Wheels are rotational, or kinetic mass, and therefore weight savings (or gains) in wheels and tires have a much greater impact on overall performance than do the various other static components on the bike.


From Wikipedia (which includes various formulas for calculating kinetic energy that my pea-brain can't fully grasp): "In other words, a mass on the tire has twice the kinetic energy of a non-rotating mass on the bike. There is a kernel of truth in the old saying that 'A pound off the wheels = 2 pounds off the frame.'" http://en.wikipedia.org/wiki/Bicycle...rotating_wheel

I assume the same holds true with cars, and explains why shaving weight on the corners yields such significant gains in acceleration.

 

I've learned the exact same thing in biking. this also holds true to all the spinning things on the engine like the flywheel, crankshaft pulley and pressure plate

 

Those are my summer rims. I use Nokian summer tires.