How to readjust RST disc brakes

[Copro]

Hi all,
Since I got the supermarket bike from a colleague I was expecting to be able to easily fix the problem with the disc brakes. But while the Taiwanese company RST offers good manuals for most of their front shock absorbers I could not find any manual for the disc brake system here:



Both brake calipers are moving to the center when I brake and I could center the brake system a little better by loosening the two screws pointing to the back of the bike, pulling the brake fully with one hand so that it automatically centered around the disc and then screwing the screws in again.
Just wanted to know if there is a possibility to also adjust the calipers according to the brake pad wear without shortening the brake cable length.
(Perhaps someone knows this kind of brake system better - which has been very common in Germany when ALDI one of biggest supermarket chains started selling bikes)

Waiting of course for this one : http://bikeride.com/requests/disc-brakes-cable/

[trevgbb]

There is usually a small locking screw tucked away out of sight at the bottom of the caliper body, frequently missed because it is covered in mud or dirt, this needs to be loosened and retightened on every adjustment.