I have replace a lot of cassettes on my 8 speed bikes over the years, but i just got a 9 speed mtb last April and had to replace the cassette today. It wasn't as straightforward as i had hoped. For some reason I couldn't get the lock ring to screw on.

I greased the threads on it, and regardless of what i did i couldn't get the threads to take hold, presumably because the threads of the lockring weren't reaching the threads in the freehub body.

So i ended up taking it to the LBS where he removed the grease, and proceeded to install the lockring by doing it upside down with the removal tool in the vice. I didn't try installing it that way, but regardless when he did it, it took hold and it tightened up. He said they never grease theirs, and that was probably the issue.

Are the tolerances really this tight for installing these things?