having worked for the California highway building, measuring and signing
department it's possible that the mileage signs varied by that much.
Averaging the error 'should' give you a fair idea of true error.  But may
not.

If you're interested I could recount the sources of error on highway mileage
signs.

Mike

> From: "Richard A. Jones" <jones@COYOTE.COLORADO.EDU>
> Reply-To: "Richard A. Jones" <jones@COYOTE.COLORADO.EDU>
> Date: Wed, 24 Oct 2001 16:47:37 -0600
> To: vanagon@GERRY.VANAGON.COM
> Subject: speedo/odo error confusion
>
> I just returned from a 3100 miles trip in El Jefe.  Well,
> 3100 according to its speedo, or rather its "odo"....
>
> I've know the speedo reads high from some time.  Then
> I watched the odometer between some mile posts and
> decided it was high, too.  I thought it was gear driven
> and should be OK even if the speedo was off because of
> the calibration of the spring.  What do I know?
>
> I have the stock size tires--185 R 14--Michelin Agilis 61s.
>
> Then I decided to take advantage of I-70 which starts
> from I-15 in Utah, with mileposts to the east.
>
> Here's what I recorded
> my trip odo             I-70 milepost
> 77.8                      0
> 186.2                    100
> 292.0                    200
> 323.0                    230 (Colorado state line)
>
> Converting to percentages:
> 8.4%
> 7.1%
> 6.6%
>
> So if I drove an arbitrarily large number of miles my
> odo error would be arbitrarily small?  What's going on?
> Why should the odo error not be roughly constant.
>
> The only variable I can think of is the day started
> cool and warmed up as I drove, but only cool/warm,
> not cold/hot.
>
> Can anyone explain this?
>
> [Trip report and photos to come later....]
>
> Richard A. Jones
> Boulder, Colorado
> '81 Vanagon   Mr Bus
> '87 Syncro Westy   El Jefe
>