Speedometer Head Magnet Gap

When Working on the Cruise Control Transducer, the magnet and speed Disks needed re-gaping because they were crashing on each other. Not having access to a gap specification, I measured the Gap between the speed cup and the magnets on the speedometer. The Gap measured 0.032 inch. Input from the "Hive" suggested that about 0.012 inch was used. ( a quality business card ) Why would the Speedometer have a Gap that is more than 2X bigger? Maybe The range of acceptable gaps is quite large.