Speedometer error

My 2000 Accord speedometer is off by about 8 mph according to my gps.
It's kind of a good thing, it'll read 70 but I'm actually doing about
62. Is there a fix for this?

TIA

Nasty > wrote in news:4b01c85e$0$4857
:

> My 2000 Accord speedometer is off by about 8 mph according to my gps.
> It's kind of a good thing, it'll read 70 but I'm actually doing about
> 62. Is there a fix for this?
>
> TIA




GPS's are not definitively accurate. There is a fairly large built-in error
in all GPS's. GPS satellites are the property of the US Department of
Defense, and the military doesn't want you having the same thing they've
got for reasons of national security. This is outlined in all the new-car
PDI docs issued by Honda for vehicles that have NAVI.

In addition to that, speedometers are designed to be "fast" on account of
liability laws. Add the two together, and it could well be 8mph at 62 or
70.

If you really want to know your car's speedo/odo accuracy, you need to
spend some time with a piece of chalk and a long tape measure.


--
Tegger

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

Surely you jest!!!

Certainly GPS's are not "definitively" accurate with locational
information, but the time traveled between too "not-so-perfect"
locations should be dead on. Speed indications should be very accurate
compared to most automotive speedometers.

Also, I am sure car makers would not design in inaccuracy to "account
for liability laws", leaving themselves open to lawsuits for short
changing owners of warranty limits. If the meter is reading too high,
the odometer is approaching the warranty limit too fast.

Lastly. A very easy method of determining speed is by the time is takes
to go between mileage markers on most highways. At 60 MPH one mile
should take exactly 60 seconds.

On 11/16/2009 8:06 PM, Tegger wrote:
> Nasty > wrote in news:4b01c85e$0$4857
> :
>
>> My 2000 Accord speedometer is off by about 8 mph according to my gps.
>> It's kind of a good thing, it'll read 70 but I'm actually doing about
>> 62. Is there a fix for this?
>>
>> TIA
>
>
>
>
> GPS's are not definitively accurate. There is a fairly large built-in error
> in all GPS's. GPS satellites are the property of the US Department of
> Defense, and the military doesn't want you having the same thing they've
> got for reasons of national security. This is outlined in all the new-car
> PDI docs issued by Honda for vehicles that have NAVI.
>
> In addition to that, speedometers are designed to be "fast" on account of
> liability laws. Add the two together, and it could well be 8mph at 62 or
> 70.
>
> If you really want to know your car's speedo/odo accuracy, you need to
> spend some time with a piece of chalk and a long tape measure.
>
>

On 11/16/09 7:46 PM, in article ,
"Piperson" > wrote:

> Surely you jest!!!
>
> Certainly GPS's are not "definitively" accurate with locational
> information, but the time traveled between too "not-so-perfect"
> locations should be dead on. Speed indications should be very accurate
> compared to most automotive speedometers.
>
> Also, I am sure car makers would not design in inaccuracy to "account
> for liability laws", leaving themselves open to lawsuits for short
> changing owners of warranty limits. If the meter is reading too high,
> the odometer is approaching the warranty limit too fast.

And Honda lost a class action suit for exactly that reason several years
ago. The warranted mileage on my '06 CR-V was extended as part of that
settlement.

>
> Lastly. A very easy method of determining speed is by the time is takes
> to go between mileage markers on most highways. At 60 MPH one mile
> should take exactly 60 seconds.
>
> On 11/16/2009 8:06 PM, Tegger wrote:
>> Nasty > wrote in news:4b01c85e$0$4857
>> :
>>
>>> My 2000 Accord speedometer is off by about 8 mph according to my gps.
>>> It's kind of a good thing, it'll read 70 but I'm actually doing about
>>> 62. Is there a fix for this?
>>>
>>> TIA
>>
>>
>>
>>
>> GPS's are not definitively accurate. There is a fairly large built-in error
>> in all GPS's. GPS satellites are the property of the US Department of
>> Defense, and the military doesn't want you having the same thing they've
>> got for reasons of national security. This is outlined in all the new-car
>> PDI docs issued by Honda for vehicles that have NAVI.
>>
>> In addition to that, speedometers are designed to be "fast" on account of
>> liability laws. Add the two together, and it could well be 8mph at 62 or
>> 70.
>>
>> If you really want to know your car's speedo/odo accuracy, you need to
>> spend some time with a piece of chalk and a long tape measure.
>>
>>

On Tue, 17 Nov 2009 01:06:29 +0000 (UTC), Tegger > wrote:
>If you really want to know your car's speedo/odo accuracy, you need to
>spend some time with a piece of chalk and a long tape measure.

Or visit a country that has discovered the mile or kilometer marker.

Tegger > wrote:
> in all GPS's. GPS satellites are the property of the US Department of
> Defense, and the military doesn't want you having the same thing they've

Bill Clinton ended that silliness in 2000.
http://www.navcen.uscg.gov/GPS/selec...ailability.htm

Any current GPS will have a steady state speedometer accuracy of .1mph.

--
Clarence A Dold - Hidden Valley Lake, CA, USA GPS: 38.8,-122.5

Nasty wrote:
> My 2000 Accord speedometer is off by about 8 mph according to my gps.

Are the tires currently on the vehicle the same size as those specified by
Honda?

I did a calculation on my (off-size) tires. Honda specified 195/60 but I'm
running 195/65. The calculation involves the static loaded radius and the
rolling circumference. For my configuration the error is 7 percent at 70
miles per hour. I just add 5 mph to the dashboard reading.

My old Prelude had a recall on my speedometer that I never took advantage
of. That would have corrected some of the error but I just do a mental
adjustment and live with it.

--
Chuck

I'm running 195/60's.

I know it's an easy thing to deal with but it's one of those things that
aren't right and I'd like to make it right if I can.

Charles wrote:
> Nasty wrote:
>> My 2000 Accord speedometer is off by about 8 mph according to my gps.
>
> Are the tires currently on the vehicle the same size as those specified by
> Honda?
>
> I did a calculation on my (off-size) tires. Honda specified 195/60 but I'm
> running 195/65. The calculation involves the static loaded radius and the
> rolling circumference. For my configuration the error is 7 percent at 70
> miles per hour. I just add 5 mph to the dashboard reading.
>
> My old Prelude had a recall on my speedometer that I never took advantage
> of. That would have corrected some of the error but I just do a mental
> adjustment and live with it.
>

Nasty wrote:
> I'm running 195/60's.

What does Honda specify for the tire size? The internal settings of the
speedometer are matched to that dimension. Note that if you match the Honda
specification your speedometer will probably read a few miles per hour
higher than actual.

You can adjust the tire size to correct the error. Start with a calculator
such as http://www.csgnetwork.com/speedocalibcalc.html

--
Chuck

Charles wrote:
> Nasty wrote:
>> My 2000 Accord speedometer is off by about 8 mph according to my gps.
>
> Are the tires currently on the vehicle the same size as those specified by
> Honda?
>
> I did a calculation on my (off-size) tires. Honda specified 195/60 but I'm
> running 195/65. The calculation involves the static loaded radius and the
> rolling circumference. For my configuration the error is 7 percent at 70
> miles per hour. I just add 5 mph to the dashboard reading.
>
> My old Prelude had a recall on my speedometer that I never took advantage
> of. That would have corrected some of the error but I just do a mental
> adjustment and live with it.


10+% is an awful lot of error. You'd need to run several sizes over
before tire diameter accounted for all of it.
See: http://www.miata.net/garage/tirecalc.html