This is strange. I swapped my old wheel on to my new frame(mondraker summum). It is a 9 speed hub, everything is tight etc I put a new sram pg970 cassette on, old one was a shimano. But the cassette seems to wide for the freehub body, the smallest cog spins when I put it in the the 9th gear and the cassette lock ring come loose pretty much straight away, it is like the cassette is too wide. Anyone ever come across this? I cannot work out what is wrong nor can anyone I have showed it to. I measured the sram and a shimano cassette and the sram is nearly 2mm wider than shimano.