Speedometer Error?

[Jondalar]

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

[T_BONES]

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

[Umai Naa!!]

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.

[Jondalar]

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

[Umai Naa!!]

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

[martinnw]

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

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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[Jondalar]

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

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

[Jondalar]

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

[Smart1]

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.

[dinot81]

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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[DETROITCANDY]

19" should have the same rolling circumference as 18" wheels. Just the sidewalls are shorter. I think mine with factory 19's was reading 114km/h on the dash and 110km/h on the GPS. What you're describing doesn't sound right.

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[Guest001]

Speedos in AUS must comply with ADR rules which put simply say that they can read up to 10% + - 4 higher than actual speed at 100kph

They may NOT LEGALLY show LESS than actual speed. If yours is reading less than actual, someone has fitted wheels of a much larger overall diameter to do that.
Our Polo reads 7 over at 100kph and to correct it to show 100 at 100 would take a diameter of 46mm more which is illegal in Queensland
I suggest you take it back to where you got them and point this out.

We have not been able to adjust the speedo calibration on either car using VCDS

Here is the best comparator to find out

Custom rims, wheel tire packages for your ride - RIMSnTIRES.com

Put the old size and the new one in and it will tell you how speedo will read Dont worry about offset it doesnt make any difference

[Jondalar]

Just to clarify the wheels were fitted to the car when sold new. The dealer had an RS buyer who didn't like the wheels so swapped them for the ones on a diesel style. Tyre size is 225/35 19, as per 19 inch black pack.

[Guest001]

Just to clarify the wheels were fitted to the car when sold new. The dealer had an RS buyer who didn't like the wheels so swapped them for the ones on a diesel style. Tyre size is 225/35 19, as per 19 inch black pack.

So what size and tyres were the ones they swapped off it

[woofy]

If you bought it like that, take it back to the dealer and get them to check it as it wouldn't pass as being a compliant car otherwise. As others said usually at 100km/hr the Skodas are usually 96km/hr or under. Mazdas are usually dead on 5km/hr under. Australian built cars are bang on the true speed.