Speedometer off 3-4 mph at 70-80mph

[Fleming23]

I have not reached out to my dealer yet, but had my cruise control set to 80 mph and though it odd traffic was all over my rear bumper. Pulled up Waze and realized my actual speed is around 4 mph slower than indicated at 80. Even at lower speeds (50 +/-) my speedometer is reading 2-3 mph faster than actual GPS speed. I am on 22" Spyder wheels, although not sure why that shoudl matter. I need to verify the odometer is reading correctly.

Anyone else noticed this? I would expect 1-2 mph, but 3-4+ is excessive, and quite annoying.

 

[daveo4EV]

this is common and an offset the germans put in all their speedo's - knowing this I adjust my Cruise Control set speed appropriately - all my Porsche's have this "offset"

I'm reminded of this "offset" every time I drive past a "you are going this fast" radar sign in various places on the highways in my local area - I'm able to note a 2-4 mph "adjustment" from what the external radar shows and the indicated speed on the dash inside the vehicle…

73 mph indicated speed on the dash of my Macan EV seems to yield 70 mph on any external measurement device…

this is similar in my 2021 Cayenne, 2022 911, 2023 911 and has been consistent with previoius year models of Porsche's I've own in the past.s

it's not a "defect" it's by design and the way Porsche sets up their vehicles and speedometer for what ever reason.

 

[rmwrip]

I have owned several BMWs. All under-reported the correct speed. I just set cruise 3 mph over what I want it at.

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