They don't "NEED" to be pressed in, heating and cooling the various pieces is much preferred to pressing any day. Although you would need to heat the hub more than sun temperature, more like 225-250 degrees. But it is much simpler, and there is no chance of scoring the various parts. We rarely use the press at work for assembly, there are a few operations that you can't heat/cool the components, but if we have the option....
