Recently I replaced crank, chains and cassette on my about 4 years old trekking bike. All parts are low priced Shimano parts, just as the ones I replaced. New crank and cassette have lesser numbers of teeth, but still sport 3 and 8 rings.
Now, when I cycle about a kilometer, the chain starts to click, like when its shifting, and even jumps, like the teeth of the cassette are worn. The first kilometer is fine, but then this behaviour sets in, no matter, how I finetune the gearshift. This behaviour can't be reproduced on a bike mounting stand, only under normal use. Bumpy roads seem to enhance the issue.
Does someone have an idea, where this issue might come from, and what can be done to solve it? I thought about trying to replace the small cogs on the derailleur, could they be the problem? All the cables (inner & outer) are the original ones, but they worked fine before I replaced the drivetrain.