Date: Wed, 24 Oct 2001 22:31:17 -0700
Reply-To: David Marshall <vanagon@VOLKSWAGEN.ORG>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Marshall <vanagon@VOLKSWAGEN.ORG>
Subject: Re: speedo/odo error confusion
In-Reply-To: <3BD74509.B96DC05A@colorado.edu>
Content-Type: text/plain; charset="us-ascii"
It is all big brother... the government doesn't want speeders, so they make
the car manufacturers install speedometers that read high on purpose. Hence
you can do 70 in a 65 zone and "get away with it" as you are really doing 65
or 66 MPH.
The best way to measure speed is with a GPS - very accurate, both in the
speedometer and odometer departments. The speedometer part can easily be
corrected by adjusting the needle - pull it off and reposition it the amount
the error is at 65mph. The odometer will require a different cog at the
pickup.
My Syncro with 205R14s installed was spot on speed wise and a little low
odometer wise (2%).
David Marshall
Fast Forward Automotive Inc.
4356 Quesnel Hixon Road
Quesnel BC Canada V2J 6Z3
mailto:info@fastforward.ca <mailto:info@fastforward.ca>
http://www.fastforward.ca <http://www.fastforward.ca>
Phone: (250) 992 7775 FAX: (250) 992 1160
. Vanagon Accessories and Engine Conversions
. Transporter, Unimog and Iltis Sales
. European Lighting for most Audi and Volkswagen models
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com]On Behalf
Of Richard A. Jones
Sent: October 24, 2001 3:48 PM
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
