11 speed freehub and 10 speed cassette, spacer question
 

Do I need to put in the 1mm spacer along with the 1.85mm spacer that comes with the wheelset? I find that my cassette is still tight even without the 1mm spacer.

if it's tight, you can tune in the der without going to extremes, & the chainline is good with the respective crank position, I would say less is more in this situation. Save the extra shim for another wheelset.

The spacer may be specific to hub/cassette combinations, and not a universal truth. For example, I have a Bontrager hub and if I use a Shimano Ultegra 10-spd cassette, I need the 1mm spacer but if I use a SRAM 1070 cassette, no spacer is needed.

With my Fulcrum 11-speed freehub and running a 10-speed Ultegra cassette, I require both the 11 ==> 10 spacer that came with the hub as well as the 1mm shim that came with the cassette.

If it's an Shimano 105, Ultegra, or Dura-Ace cassette, yes. If the cassette was packaged with the shim, yes. I believe the new Tiagra 10-speed cassettes don't use it.