before you can mount a non-standard rear wheel you have to fit the all the drive gear, rubber donuts and the spider plate that fits into them. (the spider has the drive teeth on it).
Just before this is fitted over the wheel hub an o'ring is needed that looks like it acts as a dust seal between the spider and the wheel hub its self
The O'ring slot on my new wheel is alot deeper than the stock and there for the doenst seem to fit quite right i.e needs to be slightly fatter to achieve a seal. just wonder if this was common with custom wheels if so what size o'ring are peeps using.