Hey guys,

It has just been brought to my attention that the odometer in my TF Magna is giving the wrong reading.

I found this out because the distance from home to work is 104kms (and that is what distance is displayed in both Holdens I own).

My Magna is displaying that it was 109kms from home to work and that is going the exact same route, speed, etc.

My Magna still has the original 15's fitted with 205/65R15 Yokohama tyres.

Where did the extra 5kms come from? For all I know, my Magna has only done 180,000kms or something, instead of 253,000kms.

Thanks for any help :)

Use google maps to determine the journey length

Don't worry about it. Odometers and speedos are known to be inaccurate.

Use google maps to determine the journey length

Just checked, Google Maps is saying 106kms 1 hour 42 Minutes.

Don't worry about it. Odometers and speedos are known to be inaccurate.

Yeah you're probably right, I was just concerned because 5kms is a fair difference. 1 or 2kms would be fair enough.

I don't think I've every owned a car that has had an acurate odometer/speedo. The best way to check it out is to either a: drive on a highway that has one of those odometer checking zones (big signes on the side of the road indicating exact kilometers) or b: buy/borrow a navman or download a speedo onto a smart phone and find out how far out your speedo actually is.

I don't think I've every owned a car that has had an acurate odometer/speedo. The best way to check it out is to either a: drive on a highway that has one of those odometer checking zones (big signes on the side of the road indicating exact kilometers) or b: buy/borrow a navman or download a speedo onto a smart phone and find out how far out your speedo actually is.

The speedo is about 8kms out (when I am driving 110km/h by the speedo, i'm really travelling 102km/h), but that shouldn't cause the odometer to be inaccurate should it?

I have used the 5km "speedo" check zones near Brisbane and for every 5km my TJ trip meter shows 5.2km... so every 50,000km I gain 2,000km pretty much. This isn't abnormal for a Magna, my TF was the same.
I also have a VE commodore which is actually dead accurate to the nearest 0.01km in the 5km zone. All vehicles seem to differ. I had a 94 Suzuki Swift as my first car and for every 5km it only showed 4.7km.

The speedo is about 8kms out (when I am driving 110km/h by the speedo, i'm really travelling 102km/h), but that shouldn't cause the odometer to be inaccurate should it?

It certainly will. The speedo and odometer are both operated by the same signal coming from the gearbox.

Like I said, they are not spot on accurate. I know my speed is way out, because when I do 60 in a 60 zone, people fly by me. lol Or is there some other explanation?
lol

102 when at 110? That's terrible. get some new tyres that are the correct diameter.

What about your tyre pressures? If they are on the low side, the rolling rasius will be smaller and hence the speedo/odo will under-read. I cannot comment on how much, but with higher aspect tyres such as my Pajero (235/75/15 tyres), you can see a marked difference when the pressure increases from 24 psi to 34 psi. I haven't checked our TF (mainly because it hasn't had a slow leak in the tyres (Shhh!)

What about your tyre pressures? If they are on the low side, the rolling rasius will be smaller and hence the speedo/odo will under-read. I cannot comment on how much, but with higher aspect tyres such as my Pajero (235/75/15 tyres), you can see a marked difference when the pressure increases from 24 psi to 34 psi. I haven't checked our TF (mainly because it hasn't had a slow leak in the tyres (Shhh!)

Smaller tyres cause the spedo to OVER-READ not under...

I will be replacing the tyres soon as the tread is getting low on all 4 tyres, but I have been holding out because i''m not sure whether to get new rims as well.