Radius is the distance between the center of a circle and it's outside, diameter is twice the radius, or outside to outside dimension of a circle.
So, did you measure the outside dimensions (diameter) and take off 1/8", or did you measure the radius and take off 1/8" (1/4" off the diameter). I assume you measured the diameter myself.
They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.
