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