I'm planning to upgrade from 9 to 11 speed, Sora 3500 to 105 5800.
I'd like to keep my existing mechanical disc brakes, which I believe I can, but please correct me if wrong.
Also, if I bought the full 105 groupset with rim brakes (cheaper than set with hydraulics) and just sold the brakes, would everything else still work on my bike with disc brakes?
Lastly, other than brakes, what can I get away with not replacing. Bottom bracket, shifters, crankset, FD? Thanks.