This is a quick an elementary one, but I’m having a memory lapse here. 11 speed Shimano R7000 series cassette on an 11 speed freehub body. Is a spacer still required, and if so what thickness?

Depends on the tooth count of the cassette. An 11-34 cassette will require a 1.85 mm cassette. Cassettes with smaller tooth counts don't

No spacer needed if you use a CS-R7000 cassette, which (as alcjphil explained above) technically excludes the 11-34 model, which is CS-HG700-11.

^This^

I do ALL mechanical work operating under the rule that "there are NO rules, everything is about the situation". This would apply perfectly here. In order for the system to work as designed, the cassette must overhang the freehub body by 1-2mm so the lockring can compress thecassette without bottoming against the freehub body.*



*I know that that sounds like a rule, but it follows the logic the situation trumps "rules".

That’s the exact model I have, glad I asked then! It also has the designation HG-EV and HG-X11 on it. What is the reason that this particular range has a different spacer requirement? I wrongly assumed that the cassette body with on any 11 speed road cassette using the 11 speed narrow chain would be the same.

Digging through my parts drawer I found this. Measures out to 1.84 which seems like it probably is within tolerance. Just to be clear, the spacer required for an 11 speed 11-34, is the same as the adapter spacer for an 8s,
9s, and 10 speed? Thanks for the help!

So it can fit on MTB hubs which didn't get the wider freehubs at 11 speed because the sprockets for 11-12 speed are big enough that they can start to overhang the flange inboard

Ah, I didn’t think about the MTB aspect.