incorrect speedo reading

johngalt · Post by **johngalt** » Fri Nov 13, 2009 11:50 am

Driving back from kaikoura I passed a trailer with a speed display on it saying I was doing 98 kph, when I was actually doing 103 kph. I have factory wheels and tyres . That is quite a huge difference, anyone else noticed a difference like that? Not complaining as that will keep me within the law

Stevo · Post by **Stevo** » Fri Nov 13, 2009 4:59 pm

According to my GPS, my car is doing 97kph when the speedo shows 100kph. Most cars are showing a few kph more than they are actually doing. My van is 7 kph out. Cheers Stevo

Mark · Post by **Mark** » Fri Nov 13, 2009 5:20 pm

Same here - speedo shows about 104km/h with GPS verified speed is 100 km/h. That's on stock wheels /tyres. It's normal.

poison · Post by **poison** » Fri Nov 13, 2009 6:42 pm

That sounds about right, both my previous speedo and my company car read
about 105k when my GPS says I'm doing 100k. I assume they factory calibrate
on the safe side allowing for maximum tyre wear etc.

Makes you wonder on top gear how fast some of the super cars are actually
going, I wouldn't be surprised if some companies calibrated upwards to claim
a faster car. Juts like Volvo getting caught for faking their crash results
many years ago.

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Grant · Post by **Grant** » Fri Nov 13, 2009 11:39 pm

My NA and NB cars were both fast by about 5%. The NC I now have is very
accurate throughout it's range. The error at 100km/h is less than 1km/h. All
with standard factory wheels and tyres. My previous 4wd (Isuzu Bighorn and
Nissan Terrano) were also just over 5% fast while my present Kia Sorento
indicates 100km/h when the GPS shows 99km/h. The error is slightly worse now
that the tyres have done 36000km compared to the 21000km when I bought it a
few weeks ago.
The 5% error also means you get a better fuel economy too as the odometer is
usually inaccurate by the same amount!
Grant.

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