You can't get a much better check than a WAAS enabled GPS.

 

Agreed, GPS are pretty accurate. I've never seen mine off from my correct (assumed correct) speedo or in any car which I've used my hand held GPS. I've used it in my wifes car, my car, friends car, on ATV's, on vacation in rentals, on my mountain bike and in the air. They appear to be spot on.

When I changed tire to a set of exact size as the factory tires but a differnet brand (Michelins) my GPS showed me going slower than my speedo said. So as I've said before not all tires are created equally.

 

Have you been calculating your gas mileage with Imperial gallons? Better recalculate - a US gallon is 3.785 litres. "It's so easy".

 

I use a SirfIII gps antenna w/my pda navi system. The speed shown on the speedometer on my journey (w/the 18" sport wheels) and on my maxima are definitely within 1mph of the gps speed.

 

I have a garmin navigation system in my g, and I was watching my speedometer and the speed that the garmin was tellin me. They were both the same. Maybe it was off by at most 1 mph. and this was while going 80+

 

I know on my 2005 G35X when I checked the accuracy of the speedo with the same GPS it was dead on.

 

I've checked my speedometer via GPS, mile markers, and those road side speed sensors the police put up to show how fast you are going. Within 1mph according to all 3. My truck too.

My previous car would be going at 80-82 when it showed 75. The car before that would be going a little slower than the speedometer indicated.

 

Now this has become a seriously funny thread!

Not that I've gotten much help mind you - but the good natured cross-border barbs are, well...they're just beauty eh?

Guess I'm off to the dealer then. I'll have to give them the third degree (whether in Farenheit or Celsius )

Cheers.

 

My 04 Audi S4 did the same thing,, read faster then you where going And the dealer did nothing,,, because they can't,,, thats the way audi did things, at least back then.... Its was almost 3.5 MPH @ 60.. However my 07 X appears to be like most here,, close to spot on, or less than 1 mph off.....

 

I drove past a construction zone on the highway and they had a radar sign showing driver's speed.
I went past with the ICC set to 67 and the sign read 67 as I drove past, so it seems accurate to me.

 

they could have fix it, it's that they chose not to. If you have ever gone to court over a speeding ticket, the court will ask you to prove you have had your speedo calibrated if you say "I know I was going 45 mph because I was looking at my gauge". There are such things as speedometer shops. They can be adjusted.

 

Well guys, I am also having the same problem with my G35sport 07. I have stock wheels at proper PSI and I also have between a 10 and 12 KPH diference in the speed across th eboard with the car registering much higher... I am going to the dealer next week to check this out... I also have lots of crashes on the Navi/onboard computer system when I use my bluetooth with a Moto Razr phone....The software in the car is not stable when it comes to the bluetooth...

Arun..

 

GPS is inaccurate. The triangulation that the sats do is shoddy at best. Unless you're using a high priority military receiver, the GPS guesstimates your position.

I'm a fanatic about speeding tickets (thanks to my through-the-roof insurance) so one day a buddy and I used his radar gun to test my speedometer. It says I'm going 2 mph faster than I am, at all speeds.

On another note, I've never heard of a speedometer being off by 10-12kph, that's insane! And my navi has never crashed either, though I do have some gripes about BT (though I blame the BT nuances on the experimental Windows Mobile 6 build that my phone is running).

 

It may be down to only a few meters accuracy, but when you are driving at 60mph, that can give you a pretty accurate MPH reading, since a few meters either way is little compared to how far you drive in a second or minute.

 

One comment to the original poster: If your speedo is reading high, you have little worry for speeding tickets as you would be actually going under the limit when it looks (on your speedo) as if you were.