[time-nuts] Speedometers -- bah, humbug

[Richard Moore]

Shortly after I bought my '97 VW Eurovan Camper in late '97, I  
noticed that it was reading higher than I was going as timed by  
stopwatch and mile markers. I kept measuring from time to time to  
sort of average things out. I finally complained to the dealer that  
it was about 5% high. After a lot of incidental discussion about tire  
sizes, air pressure, etc. they called VWoA. The answer? The Feds then  
required the speedometer to read not less than 2% nor more than 8%  
high -- oddly enough, 5% is the mean of this variance. I don't know  
what's required now. My '02 Toyota Highlander reads a tad less than  
1% high, based on readings from my Garmin eTrex.

Dick Moore

On Dec 21, 2008, at 9:34 AM, time-nuts-request at febo.com wrote:

> Message: 3
> Date: Sun, 21 Dec 2008 15:23:13 +0100
> From: Predrag Dukic <stijena at tapko.de>
> Subject: Re: [time-nuts] How good is my T-bolt...??
> To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Message-ID: <7.0.1.0.1.20081221151908.01e43ac0 at tapko.de>
> Content-Type: text/plain; charset="us-ascii"; format=flowed
>
> Mike,
> Thunderbolt is going to bring You from NY to SF  at exactly 55MPH
> AVERAGE,  down to the fraction of the INPH, and still there is a
> possibility that You earn a speeding ticket or two (or more) on the  
> way.
>
> Predrag Dukic   (also not an expert,  but things are not that simple
> as Your question)
>
>
> ------------------------------
>
> Message: 9
> Date: Sun, 21 Dec 2008 10:34:49 -0700
> From: "Robert Darlington" <rdarlington at gmail.com>
> Subject: Re: [time-nuts] Thunderbolt Accuracy needs...
> To: "Discussion of precise time and frequency measurement"
> 	<time-nuts at febo.com>
> Message-ID:
> 	<b3bd5fcb0812210934l1864eae2kc6df9a3f6ca14c27 at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> And faster speedometers make your warranty run out faster, which  
> nobody
> except the car companies like.
>
> On Sun, Dec 21, 2008 at 10:21 AM, Magnus Danielson <
> magnus at rubidium.dyndns.org> wrote:
>
>> Thomas A. Frank skrev:
>>> On Dec 20, 2008, at 6:03 PM, Burt I. Weiner wrote:
>>>
>>>> I suppose a good comparison would be: How accurate does the
>>>> speedometer in the car really need to be and why.
>>>
>>> Accurate enough so that if its reading matches the posted sign, you
>>> don't receive a ticket?
>>
>> An engineer pointed out that due to the spreading of readings on  
>> various
>> speedometers un-necessary take-overs where performed by those  
>> having a
>> higher speed for the same reading than those having a lower speed for
>> the same reading. Thus, the precaution is to some degree  
>> compromised by
>> the lack of consistency in the degraded reading. This is further
>> compromised by people knowing their speedometers is degraded, so they
>> form their own rules of how to interprent them in a favorable  
>> fashion.
>> The tires and air pressure in them comes in as things compromising  
>> the
>> scale. My speedometer gives different readings on my summer-tires  
>> than
>> my winter tires.
>>
>> I think I actually prefer more exact speedometer in all cars. Then  
>> there
>> is less room for subjective judgements and less of a discussion  
>> altogether.
>>
>> I think we already did some work in a similar fields like weigth,
>> lengths and time...
>>
>> I learned alot of what my speedometer told me when looking at my  
>> TomTom
>> reading.
>>
>> Cheers,
>> Magnus