Freestyle BMX brakes

HI,

I am having issues attempting to centre the brakes on a freestyle BMX I acquired from CERES BikeShed.The brakes are a Promax U brake type, something like this:On both the front and rear one brake pad is rubbing against the rim. I have tried removing the calipers from the mounts and greasing the bosses, but that hasn’t helped.I have tried the tension screws on each spring, but it doesn’t seem to be making much difference.Is there any secret/knack to getting these type of brakes to play nice?

Please help.

I didn’t find the right solution from the Internet.

References:
http://www.bicycles.net.au/forums/viewtopic.php?t=84666
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Thanks!