How Accurate Are Your Speedos

[ENVY-T]

  tab said:

At those speeds it seems to read over by about 3-4 k’s going by the average speed on the trip meter.  I.e. setting the cruise control and resetting the average speed.

Trent.

I have noticed this also. And when we past a speed check point it also registered 67 when we were doing smack on 70.

[ZAP]

The police speedo can be turned on at any dealer with the WDS.

They should do it free if they are a nice dealer.

This option will put a digital speedo in the right LCD window with a big P next to it.

The only bummer is that you loose all the trip meters, but I do not care about milage.

[harvyk]

Speedos can vary during trips...

A couple of years ago I did a trip around Vic with the missus, and there where certain point in which they had the speed radars that simply report back the speed... The first one I went past I was sitting on exactly 110KM/h and the sign said I was doing 107km/h, that seemed ok as I had been driving all day (drove down from canberra so the tires where pretty warm)...

The next day once again sitting on exactly 110km/h and this time the sign said I was doing 113km/h... The difference was that this time my tires where still cold... (It was a cold morning and I hadn't just spent all day driving...)

This was in a '02 laser with half decent tires... (Can't remember which brand) but it proved to me that the speedo can never be 100% accurate and whilst the angle which the speed radar took my speed at probably made a difference I can’t see it being a 6Km/h difference… (as each time I was sitting dead straight in my lane)

[IH8TOADS]

I hav been past those warning signs in Perth and they keep saying slow down and wont give me my speed!!! However I will test on my hand held GPS. This is pretty darn accurate. I have found in the past that putting slightly larger wheels has brought the speedo to dead accurate due to increased rolling diameter.

[AWW XR6T UTE]

I have checked my speedo with GPS, and with the original 17 inch wheels, a true speed of 97 km/h, the speedo showed 100 km/h, and with 19 inch mags it reads right, 100km/h = 100km/h on the speedo.

[Paradoxx]

Yeah I think they take that into account when producing the car also, they wouldnt make a different sensor so they make it as accurate as they can across the entire range of falcons and different wheel sizes. But still, being an electronic pickup it's much easier to adjust than having to change cog sizes! I'm surprised there isn't some sort of trim control.

[Guest Senator]

Our speedos are that inaccurate police vehicles, dont use them for speed measuring and they are deemed uncalibrated. Instead they rely on old trusty Silver Eagle, as long as its not raining or a really windy road. And if that fails, the hair dryer (Lidar) is pointed out the window. So police have no excuse for speeding unless there in a hurry.

[BADBOSS]

I tried a hand held GPS and found my speedo to read around 2kph slower that actual,so that's ok as far as I'm concerned

[YOOT]

I have tested my speedo a 6 times on the speedo check alond the Bruce Highway up to Harvey bay/Bundaburg. Its 5km starting at 0km at the first sign.

Every 1km sign I passed my trip ticked over 10m past the sign, by the 5km sign I was 50m past the sign when the trip ticked over 5km. This indicates that the speedo (which is directly connected to the trip since speed over time is distance traveled etc) is out by +1%, or in other words when I put the dial on 100kmh I am realisticly travelling at 101kmh.

This suits me fine, since I like to be able to set my speed where I want it. If I want to for 10% over the limit so speed cameras and police can't book me, then I can.

I've had this confirmed on the last dyno run I had.

I am on 17" tyres. Original SP3000s.

[saleen]

  ZapXR6T said:

I have the police speedo option and it is accurate +/-1km/h

Wouldn't yours be out cause your car runs at a higher altitude to everone else?