Unsure about new customers, but I bought my SP-M861 through aliexpress and they had DM'd me there about the replacement. I got mine quick, and have it installed on my frame already.

Quote from: wsolji on May 30, 2024, 11:42:02 AM
Hello,
I just want to ask how to mount rear XTR postmount caliper (disk brake rotor size 160mm) to that frame? I have such a adapter https://bike.shimano.com/en-EU/product/service-upgradeparts/shimano/ISMMAR160PDH.html but on first try it doesn't look like it fits.

Kind regards,
Wojtek

I'm using a 180mm rotor that the adapter from SP-Cycle's Aliexpress store seems to work with: https://aliexpress.com/item/1005005944644557.html It's listed as intended for the SP-M030, but they both use a flat mount 160mm mount, so I figured the adapter would be compatible. My brakes seem to line up well and without clearance issues on the M frame. The 160mm adapter should work fine for your use case if you want to go that route.

I ordered the frame through aliexpress, for others who did, check your messages, SP-Cycle has already contacted me about the aluminum rocker, and mine has a tracking number (though no tracking update yet).