Does an 11speed 105 hub need a spacer for a 105 11 speed cassette?

[joy of essex]

Hello,

Just swapping a 105 cassette from a Calima ( ie campag/ Fulcrum) onto a 105 hub.

Just noticed that there was a spacer on the Calima hub. I assumed that a 105 cassette doesn't need a spacer for a 105 hub. The Calima probably doesn't have one as it was built to take 12 speed.

So, do I need  a spacer or not?

[BFC]

An 11s 105 hub is designed to accept a 105 11s cassette directly, zero spacers.

(click to show/hide)

Many 11s Shimano road hubs are supplied with spacers that make them compatible with 8/9s cassettes.
And they are therefore compatible with 10s road cassettes when used with an additional 1mm spacer which isn't always supplied with the 10s cassette (depended mainly on series, DA 7800/7900 cassettes definitely had them).
Road 10s specific freehubs were limited to a small time window (2004 ish, 7800 only, they had learned by 7900!), which have taller splines and are made from aluminium, high series only, extremely rare, these don't require the 1mm spacer and are not compatible with 8/9s because they are 1mm too narrow.

I have limited knowledge of the 10s/11s road vs MTB compatibility - outside avoiding MTB disc hubs for 11s road bike builds, those hubs mostly use a dished MTB specific cassette that comes up the same width as a 10s MTB set up, that may be a different width (narrower) than a road 8/9/10 compatible freehub body.
29er MTB wheels (700c!) created a very vague differentiation between road, gravel and MTB....

Campag vs Shimano freehub widths etc is yet another can of worms.

[ElyDave]

I have a Deore XT hub laced into a drive wheel with 10sp Road cassette, around 2016/17 vintage. That combination works fine.

Cheers
Dave