On Mon, 5 Apr 2004, Malcolm Stebbins wrote:

> I use the mile/kilometer posts along the major
> highways to test the speedo acuracy.  1 minute per
> mile = 60 MPH (36 seconds per kilometer = 100 KPH).  I
> vary my speed till it takes me 1 minute (36 seconds)
> to go one mile post (km post). and then I know how far
> off my speedo is at 60 MPH (100 KPH).  How far is "too
> far out of whack" is up to each of us.

You can also use a GPS unit, if you have one, for this.  GPS speed is
pretty accurate as long as you drive at a steady speed on a straight
stretch of road for several seconds to let it stabilize.  On my Honda, I
used a GPS and a tape recorder to log indicated speeds for the actual
speeds I was interested in, and made a conversion chart to tape to the
gauge face.  Sorta like those compass error charts in airplanes.

David Brodbeck, N8SRE
'82 Volkswagen Diesel Westfalia
'86 Volvo 240DL wagon