Speedo compared to GPS

johnmb · 20-08-2005, 22:16

Well tried out a GPS Navman pocket pc version in the car today , and it would appear that if we assume the GPS to be accurate , my Octy is showing 5 mph faster on the speedo . Is this normal that they are so inaccurate .

jamlip · 21-08-2005, 00:20

Sounds about right. Depends on the rolling radius of the wheels, but on mine if the clock shows 80mph, the GPS shows 73mph. I tend to hang at just under 80 on the clock to keep things kosher.

My rallied-up Scirocco showed 115 on the clock when the GPS showed only 100mph.

GaryM · 21-08-2005, 00:46

My Golf is only ever 2-3mph out.
Have you changed your wheels and fitted tyres with a different profile?

logiclee · 21-08-2005, 05:18

My Octavia is also 5mph out at 80mph, the Fabia is a bit less around 3mph out at 80mph.

There can be as much as 3-5mph difference between new properly inflated tyres and worn out, under inflated tyres.

Cheers
Lee

spangelaregreat · 21-08-2005, 08:18

Hi,

My Octy TDI compares as follows to my GPS:-

GPS Octy

30mph 33mph
40mph 44mph
50mph 55mph
60mph 65mph
70mph 75mph

I have compared the GPS against a calibrated speedo and it is either spot on or 1mph under.

Regards

johnmb · 21-08-2005, 10:21

I am going to set the speed warning on the GPS for 75 mph , which will be 80 on the speedo . So i have not been driving as fast for these last 6 months and slowing down at cameras when i was not even over the speed anyway .

P

cheeky · 21-08-2005, 14:13

My Fabia vRS is about 7% fast whatever the speed. Well, beyond a certain point obviously I wouldn't know ;-)

lfc958 · 21-08-2005, 19:30

From 30 - 60, my speedo is 2 mph out
@ 70 it is 3mph out
@ 80 it is 3 mph out
@ 90 it is 4 mph out

you can guess the rest

gamichea · 21-08-2005, 20:51

Quote:

Originally Posted by spangelaregreat

Hi,

My Octy TDI compares as follows to my GPS:-

GPS Octy

30mph 33mph
40mph 44mph
50mph 55mph
60mph 65mph
70mph 75mph

I have compared the GPS against a calibrated speedo and it is either spot on or 1mph under.

Regards

My A6 TDI (110) is exactly the same. GPS is original Road Angel.

plumsoul · 21-08-2005, 20:59

My speedo is 4mph faster than Tom Tom Go says

johnmb · 21-08-2005, 21:37

So it would seem , that to know true speed one needs GPS , .Now all i have to do is test out the GATSO POI i have loaded , they all show up on the maps and i am getting the warning ping but so far they have all been on too far away , may need to reset the distance check . What would be the best recomendations for setting this distance .

20-08-2005, 22:16	#1
johnmb Briskodian Join Date: Jan 2005 Location: kent Posts: 402 Thanks: 19 Thanked 3 Times in 3 Posts	Speedo compared to GPS Well tried out a GPS Navman pocket pc version in the car today , and it would appear that if we assume the GPS to be accurate , my Octy is showing 5 mph faster on the speedo . Is this normal that they are so inaccurate .

21-08-2005, 00:46	#3
GaryM Briskodian Join Date: Jul 2004 Location: Nr Manchester Posts: 330 Thanks: 0 Thanked 0 Times in 0 Posts	My Golf is only ever 2-3mph out. Have you changed your wheels and fitted tyres with a different profile? __________________

21-08-2005, 05:18	#4
logiclee Briskodian Join Date: Nov 2003 Location: Notts, UK Posts: 787 Thanks: 0 Thanked 1 Time in 1 Post	My Octavia is also 5mph out at 80mph, the Fabia is a bit less around 3mph out at 80mph. There can be as much as 3-5mph difference between new properly inflated tyres and worn out, under inflated tyres. Cheers Lee __________________ Another Ex-Scooby owner. Mondeo TDCi 130 6 Speed Ghia, Octavia 1.9TDi Elegance (Now Sold), Fabia 1.9TDi Comfort and Felicia 1.9D GLi

21-08-2005, 08:18	#5
spangelaregreat Briskodian Join Date: May 2004 Location: West Lothian Posts: 118 Thanks: 0 Thanked 0 Times in 0 Posts	Hi, My Octy TDI compares as follows to my GPS:- GPS Octy 30mph 33mph 40mph 44mph 50mph 55mph 60mph 65mph 70mph 75mph I have compared the GPS against a calibrated speedo and it is either spot on or 1mph under. Regards __________________ Ever danced with the devil in the pale moonlight?

21-08-2005, 14:13	#7
cheeky Briskodian Join Date: Mar 2004 Location: Crowborough, East Sussex Posts: 960 Thanks: 0 Thanked 0 Times in 0 Posts	My Fabia vRS is about 7% fast whatever the speed. Well, beyond a certain point obviously I wouldn't know ;-) __________________ Vorsprung durch Zufriedenheit

21-08-2005, 00:20	#2
jamlip Briskodian Join Date: Jun 2005 Location: London Posts: 492 Thanks: 0 Thanked 0 Times in 0 Posts	Sounds about right. Depends on the rolling radius of the wheels, but on mine if the clock shows 80mph, the GPS shows 73mph. I tend to hang at just under 80 on the clock to keep things kosher. My rallied-up Scirocco showed 115 on the clock when the GPS showed only 100mph.

21-08-2005, 10:21	#6
johnmb Briskodian Join Date: Jan 2005 Location: kent Posts: 402 Thanks: 19 Thanked 3 Times in 3 Posts	I am going to set the speed warning on the GPS for 75 mph , which will be 80 on the speedo . So i have not been driving as fast for these last 6 months and slowing down at cameras when i was not even over the speed anyway . P

21-08-2005, 19:30	#8
lfc958 Hello New Car Join Date: Mar 2004 Location: Kent Posts: 4,039 Thanks: 11 Thanked 24 Times in 24 Posts	From 30 - 60, my speedo is 2 mph out @ 70 it is 3mph out @ 80 it is 3 mph out @ 90 it is 4 mph out you can guess the rest __________________ Steve Hello 500 Now its here

21-08-2005, 20:59	#10
plumsoul Briskodian Join Date: Sep 2004 Location: Northamptonshire Posts: 654 Thanks: 1 Thanked 0 Times in 0 Posts	My speedo is 4mph faster than Tom Tom Go says __________________ Derek

21-08-2005, 21:37	#11
johnmb Briskodian Join Date: Jan 2005 Location: kent Posts: 402 Thanks: 19 Thanked 3 Times in 3 Posts	So it would seem , that to know true speed one needs GPS , .Now all i have to do is test out the GATSO POI i have loaded , they all show up on the maps and i am getting the warning ping but so far they have all been on too far away , may need to reset the distance check . What would be the best recomendations for setting this distance .

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