The speedometer in my 2000 Beetle reads 67 when the GPS says 63 (4 miles
per hour difference at that speed ... on the safe side).

I used the GPS in my '85 Westy, during the trip to BusFusion, and (Boy
was I surprised) the GPS consistantly showed 66 whe the speedo said 65.
  Just the opposite of what it "should" be.  At least now I know.

There are speedometer shops that can calibrate them but I don't know
what they charge.

Mike

Michael Elliott wrote:
> I know this is a done-to-death subject, but I searched the archives and
> didn't turn up what I was looking for:
>
> The facts, as I know them:
>
> According to yesterday's "speedometer check" signs posted by the side of
> Interstate 8, my odometer is a smidge optimistic: when I had traveled 4
> miles, the odometer read 4.1 miles. Close enough for me. 2.5% error.
>
> The speedometer reads pretty low. According to the "Your Speed Is"
> automated trailers with giant speed displays parked on the streets AND
> according to my GPS, the speedometer is WAY optimistic: when I'm going
> 65mph the speedometer thinks I'm going 75. This is a fixed percentage:
> as I go slower, the mph error is smaller but the percentage error is the
> same. About 8 - 9%.
>
> So the odo is acceptably accurate, the speedo is not so accurate.
> Anything a fellow can do other than just mentally correct the speedo
> reading?
>
> --
>
> Mike "Rocket J Squirrel" Elliott
> 71 Type 2: the Wonderbus
> 84 Westfalia: Mellow Yellow ("The Electrical Banana")
> Carlsbad, CA
> KG6RCR
>