Speedometer Error?

[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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[Hillbilly]

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.

[Hillbilly]

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.

[Lams]

every VW group vehicle I've had prior to this Skoda, actual speed has been about 10% under shown on speedo

This Skoda though is bang on accurate, so I have to be very careful now... I notice mum's S3 also the same. I would suggest somebody somewhere made a decision to change the way things are done

[Hillbilly]

Australian built cars are bang on the true speed.

How come my VX Commodore was 5 out then on standard rims and tyres. Speedos are normally set to allow for the largest wheel and tyre combo on the tyre placard

My 100 ser Cruiser was bang on at 100kph

[Jondalar]

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

According to the brochure 225/40 R18 (110TDI)..

According to the comparator above there should be only 0.7% difference in speedometer reading.

I'm well aware of the ADR re speedo's, when we got my wife's Golf I checked it against GPS and found it almost spot on at all speeds, but always reading slightly higher than actual speed.

What I'm really trying to get at here is whether others with the 19in black pack wheels have checked speed against GPS and what the result was.

[Hillbilly]

Shouldnt have made a discernable difference in speedo reading as only 4 mill difference in diameter.

Something is strange Maybe look at the other car instead, it might be the problem speedo may be way out on it but then you said you tried yours against a GPS so ?????????????????????????????

[woofy]

How come my VX Commodore was 5 out then on standard rims and tyres. Speedos are normally set to allow for the largest wheel and tyre combo on the tyre placard

My 100 ser Cruiser was bang on at 100kph

Could be with the reduced tolerance they changed it somewhere along the line. Previously any Falcon or Commodore I've had were always bang on. Camrys as well, but recently copped a fine in a hire Camry and it was reading higher than what the radar showed so things have changed there as well.