Speedometer Error?

After following my wife home recently I asked her why she kept sitting below the speed limit, to which she replied she was doing the speed limit. I then decided to check my speed against phone GPS, two different phones and two different apps all showed my speedometer seems to read about 2km/hr low at 60 and up to 6km/hr low at 100. Since my car how the wheels changed over by the dealer from 18 to 19 I suspect there maybe some adjustment that wasn't made. Can anyone else with the 19in Xtrem wheels please let me know if their speedometer is accurate?

Cheers,
Karl

I think from factory most new cars from about the mid 2000's travel 5% under the actual speed showing on the speedometer. I dare say it's to help prevent speeding. My old Honda Accord Euro travels 5% under it's actual speed that it reads and has the original 17" wheels on it. Anyone please correct me if I'm wrong

They're always out by around 10km/h at 100.

Easy enough to compensate for, but it's nice to have a bit of fudge factor there, around town.

You guys are not understanding, my car is showing a lower speed than it is doing...

Yes, going slower than what's on the Speedo is normal these days.

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Originally Posted by Jondalar

You guys are not understanding, my car is showing a lower speed than it is doing...

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In my Golf 7, I went through the same process. Bottom line I would set the cruise to 120 in a 110 zone and drive through the speed traps no worries 👍

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No, when my car shows 100 it's doing 106!!

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Originally Posted by Umai Naa!!

Yes, going slower than what's on the Speedo is normal these days.

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When the speedo shows 60 it's doing 62-64 and when the speedo shows 80 it's doing 84-86, when the speedo shows 100 it's doing an actual 106-109

I'd check the tyre size, sounds like the rolling diameter is too big. The OZ standard allows for speedo error to be under by (Don't quote me) 10%, there is no over tolerance any more.

Which model? The cause is likely wheel diameter for inaccurate measurement. Speedo will need calibration if you plan to keep the wheels.

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