Just having my lunch and there is something which is bugging me since last night. Despite searching various forums and I can't get an answer so here goes ( go easy on me if it seems a silly question ). When measuring a steerer tube diameter it usually is 1'' or 11/8'' but when you press in the upper and lower cups surely that reduces the inside diameter by a few mm. In that case surely it stands to reason that the headset diameter should be the diameter of the inside of the cups for a good fit. Am I making it clear .