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speedometter check
- Subject: speedometter check
- From: "S. Joseph Mann" <joem@pswtech.com>
- Date: Mon, 15 Dec 1997 09:51:58 -0600
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Gentlemen,
This past weekend I made a road trip to Dallas from Austin. During the
trip I remembered the thread about the speedometer and its discrepancy.
So I decided to run a few of my own numbers. These were taken over a
contiguous 5 minute period, with the cruse set at 90 mph, over a
generally flat surface.
Miles 1 2 3 4 5
Seconds 41 81 123 165 205
=========================================
Speed 87.80 88.89 87.80 87.27 87.80
The time was measured using a Seiko chronograph accurate to two tenths
of a second. Distance was measured by noting when each mile marker
passed the A beam of my vehicle. While the cruse control was set the
speedometer needle never left the 90 mph hash mark. The vehicle has
relatively new Pirelli P700 on all four corners that are the original
factory size.
Note: discriminate measurements at various speeds between 70 and 95 mph
seemed to indicate a somewhat consistent speed difference between the
calculated speed and that of the speedometer of about 3 mph. No
correlation between the relative speed of the car and the speedo error
was found. The error did NOT increase with the speed of the car. This
seems to indicate the that error is somewhat consistent and possibly
lies in the electronics, as a possible constant. Not the tire
circumference.
BUT, I'm sure you guys knew this. :-)
Later,
Joe "Jettamann" Mann
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<HTML>
<TT>Gentlemen,</TT><TT></TT>
<P><TT>This past weekend I made a road trip to Dallas from Austin. During
the trip I remembered the thread about the speedometer and its discrepancy.
So I decided to run a few of my own numbers. These were taken over
a contiguous 5 minute period, with the cruse set at 90 mph, over a generally
flat surface.</TT><TT></TT>
<P><TT>Miles 1 2
3 4 5</TT>
<BR><TT>Seconds 41 81 123
165 205</TT>
<BR><TT>=========================================</TT>
<BR><TT>Speed 87.80 88.89 87.80 87.27
87.80</TT>
<BR><TT></TT> <TT></TT>
<P><TT>The time was measured using a Seiko chronograph accurate to two
tenths of a second. Distance was measured by noting when each mile marker
passed the A beam of my vehicle. While the cruse control was set the speedometer
needle never left the 90 mph hash mark. The vehicle has relatively new
Pirelli P700 on all four corners that are the original factory size.</TT><TT></TT>
<P><TT>Note: discriminate measurements at various speeds between
70 and 95 mph seemed to indicate a somewhat consistent speed difference
between the calculated speed and that of the speedometer of about 3 mph.
No correlation between the relative speed of the car and the speedo error
was found. The error did NOT increase with the speed of the car.
This seems to indicate the that error is somewhat consistent and possibly
lies in the electronics, as a possible constant. Not the tire circumference.</TT><TT></TT>
<P><TT>BUT, I'm sure you guys knew this. :-)</TT><TT></TT>
<P><TT>Later,</TT><TT></TT>
<P><TT>Joe "Jettamann" Mann</TT></HTML>
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