This blog posting covers this exact question -- http://www.onthedash.com/thoughts/heuers-innovation-the-rotating-tachymeter-bezel-for-race-timing/

The simple answer -- having a Tachymeter bezel that turns can allow the timing of sequential miles (or kilometers), but it is not a very effective tool for this purpose.

The more I see Tachymeter bezels -- which are parimarily fixed in place (as on the Rolex Daytona and the Omega Speedmaster) -- I realize that they are primarily for decoration, and to make the statement that this is a "racing watch" . . . kind of like the racing stripes on a car!!

Jeff

+++++++++++++++++++++++++++

: Hello All,

: I have a Viceroy Autavia, and I wonder why anyone should be able to
: turn the tachimeter scale with the bezel?
: Is it because Autavia's also came with other scales that need to be
: turned to be used? (e.g. HM scales and diving bezels)
: Or is there some other kind of use of the tachimeter scale that I'm
: not aware of?

: Thank you for your help?

: Kind regards,
: Bart