I have a CS-6700 (UIltegra 10-speed) cassette. Manufactures of both Shimano and Fulcrum are unclear in their manual, as well as the shop where I bought it for as far as I can find info online.
Online it says that they ship a spacer ring to fit 10-speed cassettes on the Fulcrum 11-ring hub.
The shimano manual (CS-6700) says "spacer ring needed on non-10speed bodyâs ".
The Fulcrum manual says âspacer ring supplied with cassette by your derailleur vendorâ.
So I put everything on with the âspacer ringâ in my cassette box (I checked the box by Fulcrum 1000 times⌠only got extra tubeless valves and QRs⌠no spacer ring to be found). But when I tighten the lockring there is still lateral play in the cogs, whereas on my old wheel and on my Tacx Neo2 there is 0.
I am so dissapointed⌠already scratched the aluminum rims multiple times thanks to GP5000 always too tight and tire spanners snapping of the rim.
To fit a 10 speed cassette on an 11 speed hub body you need a 2.85mm spacer. In my experience this is usually TWO spacers! A 1mm spacer and a 1.85mm spacer.
Sometimes the 1.85mm spacer is found on the free hub body, although sounds like yours was missing from the start. Generally Fulcrums are in a little bag.
On another note, try never to use levers to put tires on. Using levers you are in essence increasing the rim circumference and so making it even harder to put on. Try and perfect the ârollâ method and roll the tire over the rim.
Also this can happen if you arenât careful. Ruined my brand new Grail rim with a tire lever first time mounting them up. I was in a hurry to get out and ride them, it was an expensive way to learn how important proper form is in a tire install!
Thanks for all the input! I have ordered a 1.85mm spacer (1mm is with my cs6700 cassette) elsewhere. Indeed, it should have been in the box I have now confirmed, but it wasnât (in that fulcrum bag they put in the box).
Regards putting the tires on, itâs always a me vs tire fight. I swear by Conti, so I have always ridden GP4000 then GP5000. My old wheels are Easton Vistaâs (yes, my bike is that old). I donât know about you guys, but Conti is known for tight fits. So even with the roll on technique, stretching the tire by force (pushing till the last bit and then hopefully enough slack to pop it on), putting the tire in the middle of the rim etc etc. most of the time just isnât enough. Luckily, itâs only small scratches on the rim surface, so I guess I will basically ride that off in 500km, no serieus damages fortunately.
I donât know the definitive answer, but I have been browsing around for spacers quite some time. It seems MTB has different spacers with different widths than for road.
If you google around on the net using something like âshimano spacerâ or âshimano 10-11 adapter MTBâ youâll probably get a lot of hits. But be careful⌠for myself i turned out there can be slight variations and you need the exact correct one. For instance, some spacers for â10-to-11â are 1.8, others are 1.9, whereas I need 1.85. And for my hub specifically, it is important that the spacer ring itself fits in the grooves of the hub (like the cassette), otherwise the cassette wonât snug in tightly. I say this because there are also spacers that are just a circle ring with no cut outs to fit tightly on the hub.
A 1mm spacer and a 1.85mm spacer.
(Fulcrum Racing Zero Competizione with CULT ceramic bearings on my 2008 Cube Agree SL with Ultegra SL 6600 
)