Date:         Mon, 18 Jan 1999 20:48:25 -0700
Reply-To:     George Hahn <geohahn@AZSTARNET.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         George Hahn <geohahn@AZSTARNET.COM>
Subject:      Re: speedo problems
Content-Type: text/plain; charset=us-ascii

Seth C. Bruggeman wrote:
>
> my speedo reads...increasingly high as speed increases, I've noticed that my odometer reads correctly.  I.e. the speed is off, but the mileage--as far as I can tell--is right on.  This seems strange; doesn't the same mechanism control both?

Actually, I think your speedo may be operating "correctly".  Per the
Bentley Manual (p 90.30) in May 1983 the DOT cancelled the requirement
that speedometers be accurate, all they required is that they not under
state your speed.  From that point until December 1984 it seems that
"European" calibration was used which reads way high, specifically your
indcated speed is the sum of your actual speed + 5% + 6.2 mph.  Thus an
indicated 80 mph is an actual 70.2 mph.

In 1985 they returned to the old (pre May 83) tolerance of adding 3 mph
to actual speed to get indicated speed.

As you have noted, the error gets greater at higher speeds.  I've
clocked my odometer and found less than a 2% error so it appears that it
is not affected by the calibration they chose to use for the speedo.

So it's really quite easy... as you're motoring down the highway
subtract 6.2 from your indicated speed... then divide the result by
1.05... and you've got your actual speed.

Geo Hahn
84 Westy