Unsprung weight, or the weight of wheels and tires, are considered to have a significant effect on the handling and acceleration of a car or truck. Unsprung weight also leads to stress and wear on suspension components. The most common way to reduce unsprung weight is to substitute aluminum wheels for heavier steel ones.
The amount of aluminum alloy required to provide the same strength of steel weighs approximately 40 percent less than the steel. Aluminum wheels will usually weigh less than steel of the same size. However, if the aluminum wheel is manufactured with a lot of metal, the weight savings may be small. Forged aluminum wheels are much stronger than cast aluminum models and will usually weigh less.
There is a wide range in the amount of weight difference between steel and aluminum wheels. Many cast aluminum wheels from the car manufacturers weigh nearly as much as the steel models. For example, the 16-inch by 6.5-inch steel wheels on the Chevrolet Cobalt and Malibu weigh 19.2 lb. each and the optional aluminum wheels weigh 18.9 lb.
Mazda Miata 14x5.5 inches steel: 18 lb.; the same size in aluminum: 12 lb.
Suburu Legacy 15x6 inches steel: 19.5 lb; Enkei cast aluminum: 16 lb.
Rules of Thumb
For replacing stock steel car wheels measuring 14 inch or 15 inch in diameter with aluminum wheels of the same size, the weight savings will be 3 to 4 pounds per wheel. Replacing 16 inch steel wheels with aluminum should save 5 pounds per wheel. SUVs and pickup trucks with heavier 17 inch and 18 inch steel wheels can result in savings up to 10 lb. per wheel when replaced by aluminum.
Increasing the size of the wheel by as little as 1 inch when switching from steel to aluminum will often be enough to negate the weight savings. At the same time you will have a larger wheel without increasing the unsprung weight. Also, there is a wide range in the weights of aftermarket aluminum wheels. According to tirerack.com, the major online wheel and tire retailer, 17-inch aftermarket wheels for a Chevrolet Avalanche rangefrom 24 lb. to 32 lb.
The range of weight differences in wheels makes it hard to generalize when comparing steel to aluminum wheels. In most cases aluminum wheels provide a weight savings that is significant enough to notice when driving a vehicle aggressively. If weight savings is an important consideration, contact the wheel manufacturer or retailer to obtain exact weights. It is often easier to compare the total rim and tire weight to determine the total weight savings.
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