I stand corrected! totaly missed his gps comment....must be the nyquil!
cheers!

 

actually i agree with AndyCT9W, manufacturers are known to under-calibrate the speedometers, industry officials have said speedometers are set "optimistically" to give drivers an inflated sense of speed (and help them avoid tickets); and because of tire size difference that can exist even within a single model of a car, ie. between the GTS and the DE, they wouldn't risk having the liability of having the car going faster in real life than the speedo readings. (saving their a$$es from lawsuits)

gps hands down is more accurate, the vertical travel variable holds true only if there's only one satellite afixed onto the unit, which is not the case; since the earth is round and by the time several satellites are triangulated onto the receiver, the vertical variable is negligible.

and to finalize my point, a friend of mine has done test with a popo's radar and the gps wins everytime

 

You aren't going to win a court-fight of popo radar vs what your gps says.

 

when i had my OEM 215/70r16 tires, my speedo says i am faster than GPS speed.
when i changed over to 235/70r16, my speedo and GPS reading are both the same.
btw, this also hold true when i have my 235/55r18 summers on, GPS = speedo.

 

Speedo inaccuracy is a given. Almost all makes read higher than LIDAR or GPS-confirmed speed.

 

This is the correct answer, IMO.

Just think about the liability of an inaccurate speedo and contrast it with the cost of providing exactly precise equipment readings. That tradeoff is the key to consider here.

My understanding:

The way the manufacturer will deal with the actual + or - of the installed equipment (since they cannot afford to use exactly precise equipment) is by setting the displayed speed to the actual speed PLUS the + or - value. that way they don't get sued for high reading speedos.

When I took my WRX to have the speedo calibrated for a court case (vainly trying to get out of a speeding ticket) the officially sanctioned calibrator used GPS to measure the accuracy of my speedo. The speed displayed equaled the actual speed + 2 MPH

 

Remember, the satellite is roughly 1.5 million km from earth. it may be accurate to tell you where you are but I'm not sure how accurate it is in terms of speed. just my 2 cent.

 

lmao

 

lolwut? closer to 20,000km but ok.

In terms of accuracy I'd definitely say GPS, the GPS in my iPhone can tell me which room of my house I'm in. But in terms of consistency the speedo will be more consistent. If you had it calibrated, the speedo would be more accurate, keeping it mind (like all things) it's accuracy will depend on the hardware used (components in the car), the equipment used to calibrate and the calibrator's abilities.

 

Wrong answere company man! I have two other vehicles and both are nuts on to what my gps reads as my speed, try again. We are being dupped by the man as usual!

 

My 2009 Lancer GTS has a 3mph difference than my GPS which means my warrantee is expiring faster than it should!! think about them apples, what a conspiracy hope to get it fixed or verified at the dealer in a few days i will let you know what they find.