 Solution

Each concentric shell has a different circumference, so it generally needs a different integer wrapping vector $(n,m)$. Different vector lengths do not force different chiral angles, but exact atomic registry between all curved shells is geometrically restrictive. The shells can nucleate with different wrapping orientations, and strong covalent bonding within each shell dominates the weaker intershell interaction.

Consequently, it is usually unnecessary to strain every shell into a common orientation and registry; many multiwall tubes have incommensurate shells with different chiral angles. Identical chiral angles are possible, for example among suitable members of one armchair family, and should not be ruled out purely because the radii differ. Atomic indices, chiral angle and interwall commensurability are distinct descriptions.