Replacement of high density materials with Mg-alloys is an effective way of reducing wheel mass. To promote a scientific understanding on the effect of material substitution on their service performance, numerical analyses of stress and strain distributions in wheels of both 356 Al alloy and AM60B Mg alloy of same road vehicles under the same service conditions were carried out. It was found that the maximum stress is significantly reduced and stress distribution becomes more uniform in a Mg wheel due to low E-modulus of Mg-alloy in comparison with that of Al-alloy wheels.