Originally Posted by TahoeM3

The general rule of thumb is that every pound of rotating mass lost is equal to 10 pounds of non-rotating mass on a car. So if you drop 10 lbs worth of tire, it will be like dropping 100 lbs from the body. The reason is that rotating objects like a wheel require more force to accelerate. The further the weights from the center of rotation, the more force required to turn it (think of an ice skater spinning and then bringing her arms closer to her body causing her to spin faster). So run flats, which have most of their weight on the outside edge of the tire, are the worst offenders. They are absolutely the worst choice for performance but are chosen for safety reasons.

Weight is the enemy of performance, or course. Losing weight improves power-to-weight ratio, and the ruled thumb here is that every 10 lbs of weight loss in a car (non-rotating), is like adding one hp. So 34 lbs of rotating mass lost equals 340 lbs of non-rotating mass lost equals 34 hp gained. That's not even taking into account handling improvement on losing unsprung mass. I really saw a difference on my Aston Martin when I changed wheel/tires to larger but lighter ones. I saved about 15 lbs and could definitely feel it, so 34lbs will make a huge difference on this car.