In a message dated 7/7/08 1:18:31 PM, healeys-request@autox.team.net writes:
>
> The linkage between the cable and the odomoter and trip meter is hard
> gearing so it's not likely your odometer is off (if a gear was skipping
you'd read
> low). If you have lower profile tires than stock--who doesn't ;)--your
> odometer would read high (the difference between a 26" dia. tire and a 25"
dia.
> tire would cause a 4% discrepancy, for instance).
>
> Also, GPS indicates linear distance between pt. A and pt. B, and may not
> account for small turns between two points. However, I believe the newer
GPSes
> sample quite often so this may not be significant.
>
I do have slightly smaller-diameter tires (running Kelly Metric 165x15s) and
your four percent estimate isn't far off from what I calculated.
I talked to Garmin about their calculations and the journey distance that's
shown on the summary page is in fact the actual highway miles covered -- it's
calculated by using the time and speed information. (There are some distances
on the garmin that are point-to-point -- such as the distance to a gas station
or restaurant -- but the journey distance is actual miles driven.)
It's also interesting to compare the actual speed as shown on the GPS with
the speed indicated on the speedometer. For example, I normally cruise with
the
needle midway between the 60 and the 80 marks on the speedometer, which the
Garmin tells me is actually 65 mph, and occasionally go up to an indicated 80
mph when I'm in the typical high-speed urban freeway traffic (like I5 passing
Anaheim), which the Garmin says is about 72 mph.
Incidentally, FWIW on the entire trip, up hill and down, my temp never read
over 200, and generally was reading between 170 and 190 degrees. On this trip
I
was running with bottled water and water wetter in the radiator, with no
antifreeze, and I have a "Texas Kooler" plastic fan on the engine.
Cheers
Gary
**************
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