which may for example have a hemispherical shape once the balance weights 42 having the selected mass are deposited in the selected locations the rotor 40 may be tested again on the balancing machine if the rotor 40 is still found to be out of balance the above process may be repeated one or more of the segments 44 of one or more of the weights 42 may be removed and the rotor 40 tested for balance again the invention provides an improved balancing method having a number of advantages over prior methods the computerised simulation determines the correct location of the balance weights to attain a required balance state without requiring trial and error and may optimise the location such that the mass and or tensile load on the rotor is minimised as a result the overall weight of the component is minimised and or the life of the component is maximised the reduced overall weight following rebalancing can be taken into account during design of the rotor resulting in subsequent further weight reductions due to the reduced structural requirements of the rotor furthermore the balance lands can be reduced in size or omitted as material can be added directly to the disc resulting in a further reduction in weight since material can be repeatedly added or removed from a wide variety of locations no parts of the blade such as balance lands need be permanently removed thereby increasing the number of balance operations that can be carried out and consequently further increasing the potential life of the.