Too much Travel when installing Mechanical Disk Brake I am replacing the cable for the rear mechanical disk brake on my brothers MTB, because it is all chewed up. Now when loosening the cable on the rear brake (barrel adjuster on lever and brake all the way in), I noticed that there was a preload on the brake arm that pulls the pads together, meaning that the cable was clamped while the lever was already moved up a bit.
This was as it originally came from the factory. The brake is a Shimano (Alivio controls) and looks something like this with only 1 adjustable pad.

Every tutorial I found for brake installation doesn't put a preload on the brake arm, even the official Shimano service document doesn't mention to move the lever up before tightening the pinch bolt.
On the other hand I can see why it came from the factory like this, because when clamped in the arms neutral position, even with both barrel adjusters turned out, the brake would only start to grip with the lever already fully pulled towards the handlebar.
So should I preload the brake a bit when installing the new cable or what am I missing?
Without having serviced that exact design, I'd expect that at the very least you'd need to take up the slack in the mechanism. Some slack is to be expected as in similar designs the pads sit back into the housing but pass in through the rotor slot. That means more travel is needed fitting new pads than in operation, easily dealt with by a little preload on the cable. It doesn't surprise me that it's not mentioned, though maybe it would be helpful. Setting the cable position in the pinch bolt with the barrel adjuster wound in is normal for many brake types.
Preloading slightly against a spring also helps keep cable ends nicely seated.