Originally Posted by
dalava
I did some measurement and here are the results:
The cassette stack height without the lockring measure to 40.3 mm (by measuring each individual spacers and cog and cog clusters, and then add them all up). Then I double checked by measuring the whole cassette and it's very close to 40.3 mm (40.5 mm in fact). Campy's tech document says it should be 40.2 mm (+0.15/-0.05). So I think the cassette is within spec.
Then I check the free hub body width as suggested by C4L, by measuring to the base of the cassette free hub for the effective mounting area. It's 36.03 mm. Adding the 0.5 mm spacer, the effective freehub body width is 35.08 mm. Now, I have no idea if that's within spec or not.
So, I can rule out the possibility of out-of-spec cassette as the issue. Since American Classic said their hub body is not the problem (to prove it, they actually sent me a picture of another campy cassette body with measurement - the same way I measured mine - and their measurement is almost identical to mine).
What could this be?
If you study the smallest cog and the lockring, you will see that it is really the second to last cog that rests on the freehub diameter. So I believe you have confirmed you have the right parts. For some reason, you have been unsuccessful in installing the cassette. Lay the wheel on its side. Install the cassette a cog and spacer at a time. When you get to the last smallest cog you will notice it has its own integrated spacer. This nests right into the second smallest cog. The smallest cog should still key/index to the freehub spline which properly orients each cog for best shifting. Then place the lockring on top and thread it down. It should go together. I believe you were stumped because you thought all cogs should fit generously onto the frehub spline. Not so. The smallest cog almost rests on the outside and the lockring holds it all together with a thread that goes on the inside outboard edge of the freehub. If you blow up the PDF picture of the cassette to say 400% or so, it will be more clear how the last cog fits to the freehub and the lockring holds it together.
Hope that helps.