A customer ordered a rear wheel for the WH-RS170, so I sourced one.
No centering issues, just a slight wobble, but pretty much fine overall.
The rear hub spec is 142×12mm thru-axle with a disc brake mount, and
apparently they bought this wheel to use as a spare for cyclocross racing
at competition venues or as a trainer wheel at home with that same frame spec.
If you're going to keep the trainer tire on permanently and dedicate it solely to that purpose, that's one thing,
but since it uses a WO rim rather than tubeless,
using it as a spare wheel for cyclocross racing might be a bit tough.
It's mainly because of the rim weight, but this wheel falls into the heavier category overall.
The hub has the model name printed small on it,
and on the other side it says Shimano in big letters,
...wait?
This rear hub
is basically the same as the new 105 hub (↑this one)!
The WH-RS170 uses a J-bend spoke 28H spec,
but as I mentioned before, the new 105 doesn't have a 28H hub option.
While there are differences in fine finishing details,
the bearing ball race polishing specs and such are equivalent to the new 105 hub,
so it's worth considering buying this specifically for hub swap purposes.
The price difference between the WH-RS170 rear wheel and the new 105 thru-axle rear hub is about 2500 yen,
so an evil thought crosses my mind like
"if you special order the 28H spec it's just a 2500 yen upcharge(the rim and spokes are garbage)"
But really, Shimano should just offer a 28H hub for the new 105.
The old XT-badged M9000 series hubs originally came only in 32H front and rear.
Later on, for some reason they offered a 28H version for the front hub only,
and that was incredibly helpful(XT should do this too).
That's because during the transition period when thru-axles became standard in cyclocross,
there were framesets with the front at 100×15mm thru-axle and
the rear at either 135mm quick-release or 142×12mm thru-axle.
With the new XT M9100 series, both 100×15mm and 142×12mm have
28H and 32H options for both front and rear hubs.
No centering issues, just a slight wobble, but pretty much fine overall.
The rear hub spec is 142×12mm thru-axle with a disc brake mount, and
apparently they bought this wheel to use as a spare for cyclocross racing
at competition venues or as a trainer wheel at home with that same frame spec.
If you're going to keep the trainer tire on permanently and dedicate it solely to that purpose, that's one thing,
but since it uses a WO rim rather than tubeless,
using it as a spare wheel for cyclocross racing might be a bit tough.
It's mainly because of the rim weight, but this wheel falls into the heavier category overall.
The hub has the model name printed small on it,
and on the other side it says Shimano in big letters,
...wait?
This rear hub
is basically the same as the new 105 hub (↑this one)!
The WH-RS170 uses a J-bend spoke 28H spec,
but as I mentioned before, the new 105 doesn't have a 28H hub option.
While there are differences in fine finishing details,
the bearing ball race polishing specs and such are equivalent to the new 105 hub,
so it's worth considering buying this specifically for hub swap purposes.
The price difference between the WH-RS170 rear wheel and the new 105 thru-axle rear hub is about 2500 yen,
so an evil thought crosses my mind like
"if you special order the 28H spec it's just a 2500 yen upcharge
But really, Shimano should just offer a 28H hub for the new 105.
The old XT-badged M9000 series hubs originally came only in 32H front and rear.
Later on, for some reason they offered a 28H version for the front hub only,
and that was incredibly helpful
That's because during the transition period when thru-axles became standard in cyclocross,
there were framesets with the front at 100×15mm thru-axle and
the rear at either 135mm quick-release or 142×12mm thru-axle.
With the new XT M9100 series, both 100×15mm and 142×12mm have
28H and 32H options for both front and rear hubs.