2018 Golf R Speedo Error?

Is anybody else seeing a pessimistic speed? I have my radar detector set to display speed and speed limit, and I noticed it was showing higher than my dash. I downloaded a speedometer app, and it matches the detector, as well as the signs on the road to show you your speed (that also annoyingly don't have leader boards or at least a high score stored)

It seems to be consistently low, by around 5%, showing that I am going 60mph, and the GPS says 62-63.

And I am back on stock wheels and tires, deciding on what direction I want to go next with wheels/tires. I could run smaller tires to correct it, but that looks dumb.

I have also noticed this. Most road signs, etc. displaying speed show exactly the number I see, or sometimes 1mph more. Tough to say if it's the signs or the speedo. I have to assume it has something to do with the taller overall wheel/tire combo with the 19s.

--Matt

Mine seems to be spot on, officer verified.

My GTI speedo is spot on.

My 2016 R digital speedo matches my sheriff's speed signs. Air pressure at spec? I take it you didn't adjust anything electronic?

I wouldn't rely on an app or a GPS. I would ask your police department when they last checked the calibration of the speed signs.

I've noticed that both waze and my radar detector report a few miles over what the speedo says.

The Fed said:

My 2016 R digital speedo matches my sheriff's speed signs. Air pressure at spec? I take it you didn't adjust anything electronic?

I wouldn't rely on an app or a GPS. I would ask your police department when they last checked the calibration of the speed signs.

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RigWig said:

I've noticed that both waze and my radar detector report a few miles over what the speedo says.

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Tire pressure is in spec. I'm in tire sales, so I have to be on my game when I tell service advisors to be on theirs. Made a couple of adjustments in VCDS when I was visiting RocEuro, but nothing that should have any impact on the dash or speed. I'm waiting on my OBDEleven, so I can go and poke around when it gets here.

I assumed it was inaccuracy in the radar detector at first, but it matches both of my phones, as well as performance monitors on the side of the road. Four independent sources, three that match compared to one that doesn't. I'm no statistician, but I'd say the odds are not in favor of my dash.
Also, 12 around here doesn't seem to give even half of a shit about speed, apparently. I've kept the cruise at 10 over on country roads lately, and haven't been given a certificate of excellence in the arts of driving. Hell, last night I was showing 56 in a 45, in the burbs, right past the county boys, not even a pace to
get me to think about my actions.

I find my speedo to be pretty accurate. Way more accurate than any other car I've owned. All of my other cars have said I was going faster than reality. I think that's pretty typical. I find this car is within 1 mph, which is pretty good, imo.

Also keep in mind that as you lose tread depth your speedometer will continue to be more inaccurate.

The 19s with 235 rubber have 5-10mm higher diameter. I noticed this too, but when I threw on my 18 inch 225 winter wheels I originally bought for my old GTI, the speedo is dead on.

I'm guessing the ECUs across the board for the mk7 are tuned for the 18/40/225 size.

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VWs used to show fast by 7-8%, my Mk6.5 TDI wagon certainly did. 18 R is spot on.