輕鈴

Simon

The use of light-weight alloys in wheels reduces rotational mass. This means that less energy will be required to accelerate the wheel. Given that each pound of rotational mass lost provides an equivalent performance gain as a 10 pound reduction in vehicle weight, the benefits of light alloy wheels on vehicle performance cannot be overlooked.

http://www.xcceleration.com/wheel.chart.htm

Babybenz

I used to put on ultra light weight wheels on my Merc (14lbs each). The most noticable difference was in low speed acceleration.

古惑強

I read from some where else that the differential factor is x2 rather than the factor of x10, further more it only comes into effect during acceleration, and the effects will become minimal during constant cruising.

Babybenz

I recall the factor shall be 4x from some source and it helps on braking and steering control as well from my experience.

Simon

不過tire rack有呢個conclusion
http://www.tirerack.com/wheels/tech/techpage.jsp?techid=108

Vehicle        Combination        Average Speed        Average mpg
BMW 3-Series equipped with
Original Equipment (16")        Stock        38.7        22.8
BMW 3-Series equipped with
Plus One (17")        Lightweight        39.0        21.5
BMW 3-Series equipped with
Plus One (17")        Heavyweight        38.8        21.1

Simon

http://stephenmason.com/cars/rotationalinertia.html
不過據呢條友所講, 呔, 鈴和迫力碟係各有不同效果.
因為個在不同radius個mass唔同, 對個rotational inertil 都唔同.

Shaving a pound from your tires is equivalent to shaving at most 2 pounds of non-rotating weight. That's PER TIRE, so a pound off each tire could worth close to 8 pounds of weight reduction. For wheels, the multiplier is closer to 1.6, so saving 5 pounds per wheel (20 total) would feel like a static weight reduction of 32 pounds. For brake discs, it can be as low as 1.2.

古惑強

It make sense!