Great question — answering as the UphillTech team:
Mechanical disc brakes can work well, but they need to be set up just right for top performance. There are a few aspects: Pad condition : you have new pads which is good because they will be flat and clean. They can be scuffed lightly with sandpaper to be refreshed when necessary, if a little dirty, or hardened/glazed. They need to be uniformly flat and not worn unevenly, with a matt complexion. Disc condition : it needs to be running straight/true and free from contaminants like oil, but bedded in, where a fine layer of pad material is transferred to the disc to increase friction. You mention braking 40+ times, this is the bedding in process, but I start doing this very gently and increase...
Full answer by Swifty: https://bicycles.stackexchange.com/a/75960 (CC BY-SA 4.0).
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