Originally Posted by
Jipe
About my own experience, indeed, I use other components.
My Birdy was factory equipped with a hub with a standard Shimano/Sram 11s road freewheel and Shimano 11-28 11s road cassette (Pacific Cycles use the same transmission components on the Birdy R11, the only difference is that my Birdy was equipped with a front derailleur and compact 52-36 crank while the R20 has a single 52t).
I made a new set of wheels with a Hope road rear hub with a XDR freewheel on which I mounted a 11s 3T 9-32 XD cassette (XD cassettes can be mounted on a XDR freewheel, XDR means XDRoad).
What I observed is that both wheels have their cassette at the same position because there was no need to re-adjust the rear derailleur for the new wheel. The only thing I had to do is to increase the chain length by 2 links for the increase of the biggest cog from 28t to 32t. The chainline didn't change at all.
As expected, because
you replaced a road cassette with another road cassette. They are made to be compatible, in the sense that a shimano standard road hub + cassette can be replaced with an XD road hub + cassette, as long as the axle standard is the same.
The cassette spacing is the same for all/most 11s road cassettes.
Yes, the 3T 9-32 XD cassette is a road cassette. To quote Gerard Vroomen, co-owner/Head of Design 3T:
"this is a road cassette for a road bike"
https://bikerumor.com/2017/08/31/eb1...roach-1x-road/
https://gerard.cc/
11s
mtb cassetttes are a different story, see below.
Originally Posted by
Jipe
All your observations are only valid with this Sunrace system which is used on only one Birdy model of Riese & Müller and no models of Pacific Cycles. For the other rear hubs with other freewheel bodies, the situation is different.
No, it's not limited to Sunrace, it's a general issue for mtb 11 speed (not road). Yes, these Sunrace cassettes with 9t cogs only fit Sunrace hubs (except they may also be Capreo compatible, from what I hear). But the 11 speed mtb cog spacing they use is the same with Shimano and SRAM. The 1st cog is
dished towards the spokes, which makes the cassette wider than the hub body would otherwise allow,
wider than 10 speed mtb cassettes, and this moves the chainline inwards. This dishing can't be done with most road cassettes because the cogs are too small, but on mtb it's possible and a good idea in itself.
You can see the dishing in this picture (XD cassette):
https://www.bikerumor.com/ezoimgfmt/...=ng:webp/ngcb3
"The cassette squeezes 11 gears in the space of 10 thanks to dished larger cogs that hug closer to the spokes."
https://bikerumor.com/2014/08/24/fir...n-bike-groups/
"Where their 11-speed road groups required a slightly wider freehub body, Shimano was able to squeeze 11 mountain bike gears into the space of 10 without making the gears any narrower thanks to the larger low cogs. Unlike a road cassette, the big cogs can be dished around the spokes since they sit out farther, so the freehub body and the hub spacing remain the same."
https://bikerumor.com/2014/04/11/fir...ed-mtb-groups/
The dishing can also be deduced from raw spacing data:
10 speed: Sprockets are placed at 3.95 mm spacing, with each sprocket being 1.6 mm thick.
11 speed: Sprockets are 1.6 mm thick, spaced at 3.74 mm (road), or 3.9 mm (MTB).
https://bike.bikegremlin.com/1232/bi...compatibility/
The 10s inner-to-outer cog tooth tip distance is 9 x 3.95 = 35.55 mm
On 11s the distance is 10 x 3.9 = 39.0
The 11 speed cassette is 3.45 mm wider. There is no room for it to expand towards the frame dropout, so it is dished towards the spokes.
The chainline is moved inwards.
Again:
The 1st cog on 11s mtb cassettes sits closer to the centerline than on 10s mtb. The chainline is different.
Originally Posted by
Jipe
For the mentioned Shimano 11s XT M8000, as said, it was made to be compatible with a 9s-10s freewheel but this happened only once, with the XT M8000 groupset. For the latest XT, Shimano moved to a new freewheel body called microspline
M8000 may be the only one from Shimano to this standard, but the same goes for all compatible 11s mtb cassettes: non-XD cassettes from SRAM, Sunrace, Microshift, and others.
I don't know if Microspline 11s is "wheel replacement compatible" with old Shimano HG 11s - if it is, it has the same spacing as mentioned above, and the same difference from 10 speed.