If you are confident in mechanics - take spanner juggler's advice. It is more likely to be that the pads need removing and the locating surfaces given a good scrub out and clean, particularly if the pistons are free moving. Or, if the calipers, etc haven't been overhauled since new, unbolt from the axle, dismantle, clean and replace the seals and dust covers. The latter are thin rubber and delicate, over time splits can occur and damp will get into the piston bores causing stickiness and corrosion.
I have both my calipers stripped at the moment and all they have needed was a thorough clean and replacement of seals/dust covers. Under no circumstances split the caliper halves by undoing the bolts holding them together, this is a definite NO.
Exchange calipers are available at a price but will offer no more than I have suggested above.
All the best
simon
'79 Plus 8
