Speedometer Accuracy

[MLD]

Have a 2000 Accord EX V6. Recently on a long trip had the occasion to
verify the accuracy of the speedometer and was surprised to find that it has
5.7% error (reads too high) in the 60-80 mph range. On a relatively
straight highway, ran on cruise control for 3 mi and timed it with a
stopwatch. Repeated several times with the same result. So when moving
along at 70 mph ( speedometer setting) the calculated speed came out to
about 66 mph. (No wonder a cop with radar didn't bother me when I went by
him--65 mph speed limit-<g>. At this point in time don't know if the error
is in the odometer reading as I didn't run across any measured miles. I
think that since both readings are computer generated (no speedometer cable)
so am assuming the error is with the speedometer since it has a mechanical
interface. What should I expect in the way of the speedometer accuracy?
What is the typical error, anybody know?
MLD

[quadrun1]

'99 EX V6 here, I have noticed that the speedo always reads 2 mph high, that
is, an indicated 70 mph is really 68 mph, or an indicated 32 mph is really
30 mph. I verified this using those "Speed limit (low number) / Your speed
is..." radar signs that the cops put up every so often when they're bored or
whatever.

Probably not the most accurate way to assess the speedo error, but at least
it's been consistent, with the car's speedometer always reading 2 mph higher
than those radar signs.

I imagine the odometer has no error, or else the manufacturers would be
facing lawsuits from people who lease their cars (with mileage allowances).

It's not as bad as the "fudge factor" in the BMWs I've driven, those usually
read 10% high.

I forgot which magazine publishes the speedo error, it's Motor Trend, IIRC.
I think they also saw the +2 mph error in their testing.

J.

"MLD" <mdu...@email.msn.com> wrote in message
news:6qwg8.1509$L2.3...@eagle.america.net...

[snap...@cruzio.com]

In <6qwg8.1509$L2.3...@eagle.america.net>, on 03/03/02

That's not a bad error actually. The speedo is driven from the tranny
and the gears are based on the nominal tire size. Tire pressure makes
a significant difference.

jan
-----------------------------------------------------------
snap...@cruzio.com
-----------------------------------------------------------

[User]

have you put differant/bigger tires on it? and the pressure in the current
ones??

<snap...@cruzio.com> wrote in message
news:3c82bdb0$1$fancqeta$mr2...@cnews.newsguy.com...

[MajBach]

If the speedo is out then so is your odometer. Although tires sizes, wear
and inflation will cause the speedo to read erroneously, it would be as a
percentage. In other words, if the tires are to small compared to factory
ones, your speedo will read to high but say 5% to high. So at 50 mph, your
speedo reads 52.5mph; at 100, it reads 105. A 2 mph [or any fixed
number]error across the dial is not related to tires size, it is just
'calibrated' wrong. I.E., if your speedo reads 4mph when you're really only
doing 2mph, correctly sized tires are not going to change this.

"quadrun1" <quadrun1D...@optonline.net> wrote in message
news:4tyg8.43665$Iu2.15...@news02.optonline.net...

[MLD]

To your point, started the trip with the tire pressure 33 vs 30 psi (mfr
recommended). Can't see that accounting for the magnitude of the error that
I got though.
MLD
"User" <no...@none.invalid> wrote in message
news:duDg8.7813$zU2.1...@news1.news.adelphia.net...

[Dmitry]

I think it's a typical speedometer error. I have a '00 CR-V and the
speedo always reads about 3.5 mph higher than my actual speed is -
verified by GPS with 0.1 mph accuracy. I think it's "manufacturer
feature". No wonder why if you set cruise control at 70, you only
cover 66 miles an hour!

"MLD" <mdu...@email.msn.com> wrote in message news:<6qwg8.1509$L2.3...@eagle.america.net>...