Another one of my dumb questions - re. brakes

[Thejackal]

Evenin all

A silly question, and no doubt one that has been asked and answered about a thousand times, but..................

How do you centre brakes, and keep them centred? I'm running a DC1020 on the rear, that I can manually centre, however, when the brake has been pulled only the RH arm (as you are sat on the bike) seems to move and then the LH arm/ block is left rubbing the rim?

Any answers? Any advice?

My thanks 

[oldtired]

problem is the spring is not centered , when you tighten up the shaft nut the whole thing is moveing, tighten it up full then release it a bit,1/4 turn , use a drift or something to tap the spring central then nip the shaft up again and check alighnment, if its right both arms will move the same amount,    , you used to be able to get a tool to hold the springs central while tightning, dont know if you can still get em maybe LBS can help you out