Speedometer Inaccuracy
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Joined: Jun 2017
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2021 GLE 53 Iridium Silver
Speedometer Inaccuracy
Do you guys notice your speedometer is out a lot if you are driving at highway speeds? Mine is out about 7-8 km/hr when driving 110 km/hr. Mine were out with the original tires and wheels and I was hoping the new winter wheel package would fix it but it is out the same amount...
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From: Colorado
'21 AMG53 wDPP & ARC, 19 GLC300 - Former-03 C240,2 ML BlueTecs,20 GLE450 E-ABC,15 Cayenne D,17 Macan
Do you guys notice your speedometer is out a lot if you are driving at highway speeds? Mine is out about 7-8 km/hr when driving 110 km/hr. Mine were out with the original tires and wheels and I was hoping the new winter wheel package would fix it but it is out the same amount...
How are you comparing speeds? What size tires? Do you show slower or faster?
Thread Starter
Member
Joined: Jun 2017
Posts: 127
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2021 GLE 53 Iridium Silver
I also have 21 inch tires on mine. I have my radar detector (Redline 360) and portable Navigation device and both show the same however the car says I am going faster. The faster I go, the more it is out.
Out Of Control!!
Joined: Nov 2018
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From: San Francisco Bay Area
2019 C63CS
That's normal. Speedometers don't actually measure the real speed of a car. They measure the rpm of the wheels and then convert that to speed based on the tires' circumference. This circumference constantly changes with the weight of the car, ambient temperature, tire pressure and tire wear, so to avoid speeding tickets, most speedometers read higher than your actual speed. It might be more accurate on a cold morning when the tire sidewalls are still stiff, than on a warm afternoon with the tires warmed up and the sidewalls being softer. Radar detectors and your phone apps use GPS to measure actual distance travelled in a given time, which is the real speed of the car, however, even radar detectors may intentionally read high to keep you from getting speeding tickets, especially as many newer radar detectors can factor in speed to decide when to be silent and when to alert.
https://www.roadandtrack.com/car-cul...ters-accurate/
https://www.roadandtrack.com/car-cul...ters-accurate/
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Joined: May 2018
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From: Boise
2024 GMC Canyon Denali..... 2018 Audi SQ5
Mine is like yours…so accurate I keep scratching my head. I have the new R7 Uniden Radar Detector and it is always exactly the same or within 1 mph when the RD needs to catch up. I have checked mine against the roadside Radar and had a nice policeman pull me over to confirm the accuracy at 10 over posted. No ticket just a warning👍
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From: Lake Oswego, OR
2020 GLE 450; 2023 BMW M2 Coupe
Speedometer accuracy
Do you guys notice your speedometer is out a lot if you are driving at highway speeds? Mine is out about 7-8 km/hr when driving 110 km/hr. Mine were out with the original tires and wheels and I was hoping the new winter wheel package would fix it but it is out the same amount...
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Joined: Dec 2023
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2022 AMG GLC 43 Coupe
Do you guys notice your speedometer is out a lot if you are driving at highway speeds? Mine is out about 7-8 km/hr when driving 110 km/hr. Mine were out with the original tires and wheels and I was hoping the new winter wheel package would fix it but it is out the same amount...
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Joined: Jan 2020
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From: Fredericksburg, VA
2020 Mercedes GLE350 4Matic; 2023 Tesla Model Y
If your speedometer indicated speed is higher than your actual speed, it means the computer is using the wrong wheel size (diameter) for what’s actually on the vehicle (using a smaller tire size). The dealer should be able to check the tire parameter values being used in the vehicle’s software to verify they match the actual tire size on your GLE. I suspect they don’t match. Perhaps someone changed out the rim tire combo being used and didn’t update those values in the vehicle software?
Last edited by TexAg91; Dec 4, 2023 at 12:05 AM.
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2022 AMG GLC 43 Coupe
Modern speedometers are computer based, sensors count the wheel revolutions per second and multiple it by the tire size (specially the tire diameter) to calculate speed in MPH/KPH.
If your speedometer indicated speed is higher than your actual speed, it means the computer is using the wrong wheel size (diameter) for what’s actually on the vehicle (using a smaller tire size). The dealer should be able to check the tire parameter values being used in the vehicle’s software to verify they match the actual tire size on your GLE. I suspect they don’t match. Perhaps someone changed out the rim tire combo being used and didn’t update those values in the vehicle software?
If your speedometer indicated speed is higher than your actual speed, it means the computer is using the wrong wheel size (diameter) for what’s actually on the vehicle (using a smaller tire size). The dealer should be able to check the tire parameter values being used in the vehicle’s software to verify they match the actual tire size on your GLE. I suspect they don’t match. Perhaps someone changed out the rim tire combo being used and didn’t update those values in the vehicle software?
