Why is the 'radial wall' dimension $w$ critical for the clearance of the mating component?

The radial wall $w$ of a spiral ring determines the 'protrusion' of the ring above the shaft or below the bore. This is the 'retaining shoulder' that actually holds the mating part. Designers must ensure that the mating part has a contact face that fully covers the ring's radial wall to avoid point-loading the inner edge. However, there must also be clearance between the ID of the mating part (for a shaft ring) and the OD of the ring. If the mating part's ID is too small, it will hit the ring's 'ears' or 'turns,' preventing proper assembly. Spiral rings are preferred here because they have no 'ears' or lugs, providing 360-degree contact.