I'm installing a new Ultegra CS-6700 12-30t cassette onto a Shimano R-500 wheel.
The cassette is packaged with a 1mm inner spacer that fits between the cassette and the freehub.
The CS-6700 installation instructions have a somewhat cryptic note that "If using a special freewheel, a spacer is not required" but it doesn't give any information about what a "special" freewheel means in this context. <and yes, they use the term "Freewheel" not "Freehub">
Here's a link to the installation instructions; see the gray box on the LH side of the page:
The previous cassette was a Shimano 5600 12-25t, and it had the spacer installed but since I bought this bike used I have no idea about its prior history.
So I originally installed it with the spacer since there was one installed behind the old cassette, and since there didn't seem to be anything "special" about the freehub. It all seems to fit, but clearance between the chainstay and chain on the 12t inner cog is none too large and I thought it would be prudent to see what y'all think.
The bike is a new-to-me 2009 Specialized Roubaix (stealth gloat) and the drive train is Ultegra 6700/6703 triple, if that makes a difference.
Thanks in advance for your help!
-Tom in SoCal