Is the SRAM OG-1070 10 speed cassette completely compatible with shimano 10 speed? Chain, hub, etc… I know this might be a stupid question, gotta ask though.
yes
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Yes - works fine. Some will say to use the SRAM chain with SRAM cassette, Shimano with Shimano, etc. (slightly different ramps, beveling or some such) though. I find the missing teeth so strange, but works fine.
Just to throw a wrench in your spokes, I tried to get it to work (have full ultegra) by taking out the 11-23 ultegra cassette and tossing in a 11-27 sram cassette. Shifted like shit. Took it to the LBS, same story. Buyer beware, but then again, seems to have worked for some people…
I have mixed and match SRAM chains and cassettes on two bikes with no issues. There is one incompatibility that I know of. SRAM cassettes will not fit on the original 7800 D/A hub.
Chain, hub: definitely.
Rear derailleur: yes, though you may have to adjust your shifting to get it to work, because of the wide range of gearing. It should work fine, but if for some reason the shifting is poor when you slap the cassette on, you might have to adjust the derailleur.