If you look in the Bently manual it states (somewhere) that the speedo is
purposly set to read about 5% below actual speed in order to meet us DOT laws.
It also explains the number stamped below the VDO. Unfortunately my Bently in
in my Westfalia - so I can't look up the page number.

The question is if using the number to calibrate still means that the speeo
will read 5% slow?

Dr. Rainer Woitok wrote:

> Hi Larry and all you other listees,
>
> On Tue, 1998-08-11 12:15:25 -0000, Larry Carter wrote:
>
> > ...
> > I have an 87GL, the little number under the VDO is 500.
>
> Hummmm ...  Though I can remember having   read myself that  this little
> number specifies the number of revolutions of the speedo cable necessary
> to increment the odometer by one, I slowly start to  doubt that (way too
> many  different numbers for  otherwise identical set-ups with respect to
> measurement systems and tire sizes) ...
>
> > ...
> > In my GL the speedo cable (inner) plugs into a square hole punched in the
> > left front outer wheel bearing dust cover, from there the cable goes
> > directly into the back of the speedometer, there are no gear reductions
> > along the way.
>
> Please excuse my impropper wording (and my lack of knowledge of American
> technical terms; I'm trying  to catch up, though :-).   What I wanted to
> say is that  there is some sort   of simple mechanical gear involved  to
> convey the rotation of  the (more or  less) horizontal axle stub of  the
> front wheel to the (again  more or less) vertical  speedo cable.  And in
> chosing  the  diameters appropriately you  can   do anything here,  from
> spinning the speedo cable N times while  the front wheel turns only once
> to turning the speedo cable one time while the  front wheel is turning N
> times.  And because a speedo is probably  more expensive (and more bulky
> to  store)  than  such  a  simple gearing  device,  and because  in some
> countries  there  might also be  legal  constraints against exchanging a
> speedo (because  of  the odometer) I think   VW has chosen  to have only
> rather  few  different types  of  speedos  and  to   do  all the  "math"
> associated with miles, kilometers, and tire sizes using different speedo
> gear assemblies on the front wheel.
>
> I Hope this clarifies a bit what I wanted to say.
>
> Sincerely
>  Rainer
>
> PS: Going on  vacation this  Friday for four  weeks I've  set my Vanagon
> list options to NOMAIL (aproximately one hundred messages a day times 28
> days would otherwise sum up to having to wade  through almost 3000 mails
> just from this list  upon returning  :-).   Thus, if I don't  any longer
> engage in  this discussion  (or  any other  discussion for that matter),
> it's  not because  I lost  interest,   but rather because I  temporarily
> turned to more important things than sitting in my office ... :-)
>
>  ----------------------------------------------------------------------
> | Rainer M Woitok                  | Phone: (+49-9131) 85-7811, -7031  |
> | Regionales Rechenzentrum         |                                   |
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>