RE: [ST] new lister with license in jeopardy

["Daniel Wallander" <triumph99@xxxxxxxxxxxxx>]

> [Original Message]
> From: Neil Lindsey <neillindsey@xxxxxxx>
> To: Triumph Sprint ST List <ST@xxxxxxxxxxxxxx>
> Date: 1/26/2004 5:32:16 PM
> Subject: RE: [ST] new lister with license in jeopardy
>
> It has been pretty well documented that our speedometers are 'optimistic'
> and that the odometers are pretty well bang on (except when you consider
> tire wear or brand change).  As a side issue, this also means that you
> cannot do anything external to re-calibrate the speedo since you will
screw
> up the odometer accuracy in the process.

True.  If you attempt to correct the speedo error, you will also introduce
an error into the odo as they both use the same pulse from the front wheel.


>
> Many have also noted that the speedo error seems to be non-linear (ie.
not a
> fixed % error).  The ST speedo is, for the most part, mechanical in
nature,
> so one might wonder how this can be, since, in my mind anyway, an internal
> speedo gearing 'adjustment' that only affects the speedo would produce a
> constant error ratio.  The electronic speedo on the RS presents an
entirely
> different situation, so I won't confuse things by including it in this
> discussion.


The ST speedo is electronic also.  It just uses a needle instead of  a LCD
display.  The Road Speed Sensor (as Triumph calls it) at the front wheel is
hooked to the speedo/odo by a wire through part of the wiring harness, not
by physical cable.  I've never opened the speedo, but I would be willing to
bet small amounts that there are few, if any gears in there.


>
> My theory is that the FACE of the ST speedo dial has been rotated slightly
> counter-clockwise to produce the higher-than-normal readings.  If you
think
> about this for a sec, I believe you will realize that this produces a
> non-linear discrepancy between the indicated and actual speed.  This is
> because the speed increments that are painted on the speedo face are
evenly
> spaced.  For example, a 5 mph error at 30 mph will be the same 5 mph error
> at 60 mph, but the % error would be different.


Because the speedo/odo are electronic, they could have fixed the speedo
electronically very easily; by a fixed percentage (i.e. 8%), by a fixed
error (i.e. 5mph) or they could have used some kind of variable based on
any other variable with a simple silicon chip.   I know that on my bike, at
75mph actual per my gps, I am traveling 82mph indicated - about an 8%
error.  At 30 mph and an 8% error, I would see about 32.5mph (my bike
indicates a bit less than this at 30mph actual).  

If the speedometer face were rotated, I would see 82 mph at an actual 75mph
and 36mph at an actual 30mph, which I don't.

I believe it is more likely the speedos are off by a fixed percentage, than
a fixed mph.




Dan Wallander
Albuquerque, New Mexico
www.danwallander.com 
Triumph Sprint ST :: BMW R90/6
TSRA-VP, ABC#6313, IBA, HSTA




     *   *   *   *   *   *   *   *   *   *   *   *   *   *   *   *   *   *   *
      The ST/RS Mailing list is sponsored by Jack Lilley Ltd.
          http://www.TriumphNet.com/st/lilley for more info
   http://www.TriumphNet.com/st for ST, RS and Mailing List info

=-=-=-= Next Message =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=