In the low-pressure casting process, light-alloy wheels are literally produced from one casting. The liquid aluminium is pressed into the cavity of the rim casting mould from below with gas pressure. During the gradual cooling process, the pressure is maintained. This serves to keep fresh melt flowing in and compensate for the shrinking volume caused by cooling. It results in a uniform material density.
Because the aluminium melt is introduced from below, the solidification of the new wheel should take place from top to bottom. The designers of the wheel take this requirement into account, for example, by favourably grading the cross-sections. The casting is followed by heat treatment to give the alloy even more strength. All rim blanks are X-rayed to exclude inclusions or cavities in the material.