I'm changing out my wife's bike's cassette.. She has some shimano 10 speed.. probably a 105 or ultegra.. I tried to swap it for a sram rival 1070 cassette which I thought would work.. but when I took out the old cassette and put in the new one, the cogs do not fit in tightly. They are loose and move around in the wheel hub. I could add an extra spacer at the bottom of the 28T cog but its still a lil loose.. and the shifting goes all weird..
What am I doing wrong?