Speed

[nuradh]

hi everyone,
my vz commodore has 225 x 50 x 16 in tyres put on by the previous owner. The tyre placard on the driver door says 205 x 60 x 15 in, but overall diameter of the tyres should be the same or pretty close i thought.

Any way, when the speedo in the dash is compared to our navman (newly bought) the car speedo reads 5 - 10 km more than the actual speed as per the gps. Because the correct speed is not sure i may get a speeding fine.

Is my car speedo is wrong? And how can i adjust it please?. Your help is appriciated - thanks.

[crew chief]

So let me get this right......when your speedo says your doing 60 your actually doing 50-55 and are worried about getting pinged for speeding. Seems to me there is less chance of getting done. Most cars read this way.

[2005vzute]

Any way, when the speedo in the dash is compared to our navman (newly bought) the car speedo reads 5 - 10 km more than the actual speed as per the gps. Because the correct speed is not sure i may get a speeding fine.

it says the speedo reads 5-10 km/h MORE then the gps...if he's going 60 according to his gps, he's afraid that he might be doing 65-70, as it is saying on his car speedo

true?

sorry i can't help you with this one mate

[crew chief]

it says the speedo reads 5-10 km/h MORE then the gps...if he's going 60 according to his gps, he's afraid that he might be doing 65-70, as it is saying on his car speedo

true?

sorry i can't help you with this one mate

correct..... what i said still stands if his SPEEDO says hes doing 60 his gps will say hes doing 50-55. Moral of the story ignore using the gps as a speedo.....True????????

[sleepa]

if your speedo is higher than the GPS, you have nothing to worry about if you keep to the right speed. GPS is always right.

It seems pretty normal, maybe a slight difference but not too bad.

[2005vzute]

ohh i get where your coming from crew chief, my mistake..well, it depends what speedo is right..if you've used your car speedo up untill recently and gone 55 through 60 km zones where there is a speed camera and haven't been booked, everything will be sweet...you'll have to find out which one is giving you the wrong reading

[nuradh]

thanks for the inputs mates. so is there a way to tweek the speedo?

[QldKev]

thanks for the inputs mates. so is there a way to tweek the speedo?

Not sure if you have the V6 or 8? On the LSx series you can adjust it in the PCM.

QldKev

[Astranomical]

You'll probably have to take it into Holden and get them to do it with the Tech2.

For what its worth as others said the speedos on most newish cars are calibrated to display the speed as slightly higher than you're actually going. I know the speedo in my 2007 Astra is 5 k's out. (my car has a hidden diagnostics menu that gives you a digital speed readout, for example if I'm driving at 100 km/h the digital readout will say 95) As long as its saying that you're doing faster than what you're actually doing, and not slower (for example, saying you're doing 60 when you're actually doing 65) you shouldn't have anything to worry about.