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Subject:Re: Speedo calibration
From:Todd Last
Date:Fri, 21 Aug 1998 00:45:21 -0700

FYI - TODD

From Bentley manual page 90.30 (Spedometer Calibration)

Speedometer Head

As of May 1983 the existing regulations (FMVSS127) concerning vehicle speed
regulations were cancelled by the Department of Transportations (DOT).
Starting May 1983 the only requirement is that the vehicles's speedometer
indicate a higher speed than is actually being driven.

Speedometers having European calibration specifications were installed in
vehicles for model years 1984 through 1985 (Until December 1984 production).
These Speedometer heads have a basic tolerance of (+) 6.2 miles per hour with
an additional (+) 5% of the actual speed driven.

For Example:

Actual Speed            50 miles per hour
+ Basic Tolerance       6.2
+ 5% of actual          2.5

= Maximum indicated speed = 58.7 miles per hour.

Speedometers with the former FMVSS 127 calabration are installed starting
with December 1994 production. These speedometer heads have a tolerance of
(+) 3 miles per hour

For Example:
Actual Speed        50 miles per hour
+ Basic Tolerance  3 miles per hour

=Maximum indicated speed = 53 miles per hour.

NOTE: It is required that the vehicles be equipped with OEM tires and wheels
showing only normal tire wear.

ODOMETER

The Odometer reading is independent of the spped indication and is regualted
by the Federal Trade Commition (FTC). The toleracne of the odometer
indication is (-) 1% to (+) 3.5% of the actual miles driven

NOTE:

The number printed on the speedometer face plate beneath the word MPH shows
the number of revolutions required by the speedometer cable multiplied by 100
to travel a distance of 1/100th of a mile (52 feet, 9.5 inches)

Victor Montgomery wrote:

> I cannot believe Todd Last's comment regarding the 5% planned speedometer
> error for DOT regs in the US. All police speedometers are required to
> "certified" as to accuracy and regular speedometers are engineered to be
> accruate at the time of manufacture.
> Victor...
> Deutsch Amerikanischer Polizei Verband
>
> >On Wed, 1998-08-12 02:08:15 -0700, Todd Last wrote:
> >
> >> If you look in the Bently manual it states (somewhere) that the speedo
> is purposly set to read about 5% below actual speed in order to meet us
> DOT laws.<<
>
> BELOW??   That's interesting.    In   Germany speedos  are  required
> to_exaggerate_ your speed so nobody controlled by radar could claim it
> wasonly because of the speedo ...
>
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