Because wheels are considered un-sprung weight, additional fuel savings
are realized due to mass moment of inertia, where less effort is required to
rotate a forged aluminium wheel that weighs half as much as a steel
In testing performed by an independent testing and research firm, the
Alcoa aluminium wheels demonstrated an improvement of 3% in tyre rolling
resistance over a steel wheel. This reduction in rolling resistance translates
in a fuel saving of 1.0%.