I have recently bought a set of new Mavic Aksium's and new Ultegra 9 speed cassette. However when I fit the cassette there is a small amount of play, the last sprocket is about flush with the hub, it is seems that a thin washer or shim may be required about 1mm thick. Can anyone offer advice to whether this is usual? It is not the spacer for 7/8 speed that is needed it is much too thick!