Digital speedo/police police pack function and changing the speedo

[Jezza]

i have had the police pack mode(or Digital speedo) enabled on my car for almost a year now but while out cruising the others think im speeding but im not and im just doing what the speedo says which got me thinking that when 'police pack' is enabled does it take out the margin of error and shows the exact speed your doing? because i find most traffic seems to go a couple kms slower then what im doing most of the time and i only just thought this may be the reason

 

[CAPRILICIOUS WL]

Do you have bigger wheels/rims than the stock size??

 

[mmrdb]

Having larger rims will affect the speedo reading. The larger the overall diameter (includes rims and tyres combined), will cause the speedometer to read slightly slower than actual speed. I suggest you get your speedo checked!

 

[Jezza]

i have 18" wheels with the correct tyre size to match

 

[VK SL 3800]

My brothers police pack Vx is the same, the digital speedo reads slower then the analogue speedo even though they get their speed from the same sensor.

 

[WELSHH]

I have the digital speedo and it reads exactly the same as the analog speedo

 

[DevilDRake]

^ as said above.

 

[acarmody]

^ as said above.

ditto .

 

[Fletch_QLD]

Margin for error means exactly that - a margin that allows for the error in getting an exact reading. It's not a deliberate recalibration that is designed to slow us all down. The fact is that there are too many variables to get a spot on dead balls accurate speed reading. Tyre pressure, tyre wear, atmospheric variables and vehicle load all contribute to fowling an accurate speed reading.

As for differences in the analogue/digital speedos in the same car - my understanding is a little dated, but I believe there is a spring on the needle that shows analogue speed - this could be subject to wera and the springiness could fade over time - thus the number it points at begins to differ from the input signal, of course the number shown on the digital display will always match the input signal - the advantage of digital over signal is a reduction of this kind of loss.

IMHO - there is no way to make speedo reading more accurate by 'flicking a switch' with a tech 2. The speedo could possibly be recalibrated per individual vehicle, but as it's tyre and other characteristics change, the accuracy would begin to deviate from true.

my 2.5¢

 

[TMM]

I have the police setting enabled and my digital and analogue gauges show exactly the same thing. I've also verified it with a GPS and my dash reads 1km/h higher then true (e.g. when the GPS says 99km/h, the dash says 100km/h).

I believe for the analogue gauge you can disassemble the cluster and reposition the needle as required.

Having larger rims will affect the speedo reading. The larger the overall diameter (includes rims and tyres combined), will cause the speedometer to read slightly slower than actual speed. I suggest you get your speedo checked!

Not always the case. For instance the 16" wheel/tyres i have on my car are even larger then standard 18". That's probably half the reason i get such an accurate reading rather then the usual 'over-reporting'.
225/55R16 - 326.95mm
235/40R18 - 322.6mm