Magura rim brake does not work well on a new rim I have a bike with 20inch wheels and Magura HS11 rim brakes. On the rear wheel I have just replaced the rim, because the old one had split after many thousand kilometres. The new rim is an Alex  DM24 406X24. The old one was another wide aluminium rim.
The Maguras were braking fine with the old rim. In contrast now with the new rim the brakes do not work well: After some initial moderate stopping power the brakes do not grip harder when I pull the lever harder.
To explain it a bit more in detail: When I press the lever slightly (say, of a “feels-like’ amount of 10%) the brake reacts as expect by braking of “10%”. But when I press hard, say 50% or 100% (=as hard as I can), the breaking power does not increase at all, it stays at around 10%.
I am pretty sure it is not an issue with the brake system (oil, etc), because when pulling the lever I feel that the pressure against the rim increases. (Furthermore, not oil is leaking out and the brake behaviour is consistent over days.)
I guess it must have to do with the brake pads an the rim surface. The rim looks to me like it has normal alloy sides, so I kept using the old black brake pads.
So, what might cause this strange behaviour? Should I replace the pads with pads of another type? Or is there another fix?
As it turned out, the problem were not the brake pads. The issue was cause by the fact that the new rim is slightly  narrower. The brake cylinders still touched the rim, but were the already nearly fully extended out. This lead to the particular situation that the brake started breaking lightly, but full force coupled not build up, because the two cylinders had reached their maximum extension before that.

The fix was easy: I moved the brake cylinders (in the released position) further in and now they are gripping the rim again properly.