Date: Wed, 12 Aug 1998 02:08:15 -0700
Reply-To: Todd Last <rubatoguy@WORLDNET.ATT.NET>
Sender: Vanagon Mailing List <Vanagon@vanagon.com>
From: Todd Last <rubatoguy@WORLDNET.ATT.NET>
Subject: Re: Speedo calibration
Content-Type: text/plain; charset=us-ascii
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 ... :-)
>
> ----------------------------------------------------------------------
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