speedo
10-02-2020, 05:16 PM
#2
Burning Brakes
Speedo
10-02-2020, 05:19 PM
#3
Nordschleife Master
Thread Starter
^ok I was thinking the other way round, never been pulled over and always am doing 20 over, passed a opp 20 over and all he did was pull out and follow me. So I was thinking the gps must be the real speed.
10-02-2020, 05:25 PM
#4
Instructor
GPS is accurate to fractions of an inch and tenths of kph. Speedo depends on tire diameter and analog gauge.
Trust the GPS. And speedos are tuned to be high to make sure you can't blame auto manufacturer for your ticket.
Trust the GPS. And speedos are tuned to be high to make sure you can't blame auto manufacturer for your ticket.
Last edited by dml; 10-02-2020 at 05:27 PM.
10-02-2020, 07:09 PM
#5
GPS is correct
10-02-2020, 08:04 PM
#6
This...
The speedos in general on German cars read higher than actual because of TUV rules. Because the cars come with different size tires, they don't want the driver of the car to be caught speeding.
On my Cayman it is about 4 to 5 kph off... I set my cruise control at 123 kph on the digital speedo and that gives me a GPS or real speed of about 118 - 119 kph.
Last edited by Jet Jockey; 10-02-2020 at 08:07 PM.
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10-03-2020, 12:01 PM
#10
GPS would be more accurate. With speedo reading high, car warranty would expire quicker than normal for crossing the max kph under warranty, if you did a lot of travelling. At 3% discrepancy 82,400km should be still within the warranty period ( within 4 yrs )
10-03-2020, 12:19 PM
#11
Burning Brakes
You are assuming that the odometer is in step with the speedometer. I don't think that is necessarily the case with modern vehicles.
10-05-2020, 12:47 PM
#13
so it depends, both could be wrong
Speedo is always optimistic by a few percent...usually 3-4% over assuming no variation in tire size etc.
GPS is likely more accurate but what GPS are you using? Is it built into your phone or are you using an external GPS to take the reading? Phone GPS is 1Hz refresh. To get an accurate reading you need a 10Hz or at the very least a 5Hz. On Mosport for example, I've seen 10-15km/hr differences on Andretti between speedo/phone/phone with external GPS
With a built in GPS its sort of luck of the draw as to when it takes the reading unless you're holding at that 243km/hr top speed for a few seconds. There's wide variation on Mosport because you brake right after hitting top speed .
Speedo is always optimistic by a few percent...usually 3-4% over assuming no variation in tire size etc.
GPS is likely more accurate but what GPS are you using? Is it built into your phone or are you using an external GPS to take the reading? Phone GPS is 1Hz refresh. To get an accurate reading you need a 10Hz or at the very least a 5Hz. On Mosport for example, I've seen 10-15km/hr differences on Andretti between speedo/phone/phone with external GPS
With a built in GPS its sort of luck of the draw as to when it takes the reading unless you're holding at that 243km/hr top speed for a few seconds. There's wide variation on Mosport because you brake right after hitting top speed .