Was it a brand new set of Spoon Calipers? The Spoon Calipers should come with 3mm washers to fit between the caliper and the mounting point on the Hub, otherwise they will hit the disc and wont allow the disc to rotate freely. If they are 2nd hand then the washer may not have come with them, but all you need is some 3mm washers to space the caliper out alittle.
Hope this helps.