PLEASE help me with my brakes
 

i have shimano 105 brakes from '87, and one brake pad is hitting the rim(very lightly if touching at all) and so i adjust it by turning the bold pictured below with the wrench on it, once i do this both pads hit the rim at the exact same time and it seems to be tuned perfect, but after even a short ride its hitting again!, so what do yo uthink is off?, wheels are true btw

You've got the right idea but you also need to stuff an allen key into the tube nut in the back and tighten it into the new position.

If it still keeps creeping on you then you may need to strip the pivot down and clean then lightly grease the bushings and plastic bearing liners. Or your housing is creeping and pulling up on the arm side. For the centering tension balance to work the housing cannot creep since it forms a spring that will fight the centering springs of the caliper. Ensure that the housing stays in place and then that the tubular nut is tight and that the arms are not stiff and you'll find braking Nirvana.

what must i tighten(?) to make the adjustment stay?

yea, that nut is tight but now that i think about it i should loosen it, adjust the front nut then re tighten the back allen key one to hold the new adjustement right?

oh and thanks BC

Yeah, you've got it. But remember that the brake housing is a part of the BALANCED spring tensioning of the arms. It MUST stay stable. If that means you need to tape it to the top tube to hold it in place then so be it. I had one bike that the housing wanted to stretch tight over a few days thanks to the steering curve pulling it through the guides. For some reason this gentle front "pumping?" action left the segment from the last guide to the caliper tight like a violin's G string. Once I taped the housing to the top tube this stopped and I didn't need to pull the housing back anymore. Granted my case seemed extreme but it's just one of life's great mysteries... :D

Oh, and to help avoid the housing grinding into the paint wrap one turn around the top tube and THEN the next one or two turns holds the housing in place. That way the paint is protected.

sounds good, ill see how this adjustment holds up