D4 speedo vs Hema HN7

[Garfield]

I was travelling up the Hume Hwy again and noticed D4 speedo at 100 km/h but Hema HN7 states speed is only 96 km/n. Which one is correct ????????
I am running 265/60r18 - compared to original 255/55r19

[LGM]

My D4 at 96km/h indicated on the speedo is 90km/h according to my HN7 and at 116km/h indicated on the speedo is 110km/h according to my HN7......that could be why the police cars going the other way never bat an eyelid as I sit on 116km/h with my cruise control set. There are many other comments on the error / inaccuracy of the D4 speedo (factory set I believe) on this site in numerous threads.

[DiscoMick]

Legally the speedo cant read less than your actual speed. Usually speedos are set so the actual speed is 3-4 kmh less than the speedo. So your GPS would be correct. In some states speed cameras are set with a 3 kmh error margin.

Sent from my SM-G900I using AULRO mobile app

[Narangga]

Grab a coffee, pillow and a blanket and settle in to read this thread...

http://www.aulro.com/afvb/l319-disco...do-vs-gps.html

[BMKal]

I was travelling up the Hume Hwy again and noticed D4 speedo at 100 km/h but Hema HN7 states speed is only 96 km/n. Which one is correct ????????
I am running 265/60r18 - compared to original 255/55r19

Yours sounds about the same difference as I get on mine. I am running 265/60R18 Mickey Thompson tyres - if I set the cruise control on 114 km/hr and sit on this speed, the Hema HN7 indicates 110 km/hr.

When I had the slightly smaller diameter original tyres on the vehicle, I would set the cruise control on 116 km/hr to achieve an indicated 110 km/hr on the Hema HN6 that I had in the vehicle back then.

Australian Design Rules require that the speedo in all new vehicles read "safe" - that is, the speed must read greater than or equal to the true speed of the vehicle, by an amount not more than 10 percent plus 4 km/hr.



So in answer to your question - the speed indicated on your Hema HN7 is far more likely to be correct, subject to the accuracy / limitations of any GPS device.

[Garfield]

Sounds like a dicky speedo on my new D4. Came back down the Hume Hwy this arvo and went through the overhead speed detector. D4 112km/h, HN7 GPS 108 km/h and overhead speed detection 108 km/h. This probably some up why a number of people are passing me.
I knew speedo's these days had to be conservative by regulation but by 4 km/h at highway speed ???

[LRD414]

Sounds like a dicky speedo on my new D4. Came back down the Hume Hwy this arvo and went through the overhead speed detector. D4 112km/h, HN7 GPS 108 km/h and overhead speed detection 108 km/h. This probably some up why a number of people are passing me.
I knew speedo's these days had to be conservative by regulation but by 4 km/h at highway speed ???

4km/h difference ..... not faulty, that's exactly as per Brian's post.
Did you read the regulation he posted?

Cheers,
Scott

[shanegtr]

Interesting point that "There is now no requirement to have an odometer"

[Garfield]

Yes, the speedo regs that Brian posted are spot on with regards to my D4 speedo - conservative by 4km/h. Will just have to mentally just my conscious to 114km/h down the Hume Hwy from now on

[BMKal]

Interesting point that "There is now no requirement to have an odometer"

Dodgy Brothers used car sales will no doubt use that to their advantage I'm guessing.