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Author Topic: Speedo Clabration  (Read 7372 times)

Offline ljc19630

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Speedo Clabration
« on: October 28, 2019, 06:55:41 pm »
Evening fellow GTi-ers
Does anyone know the average MPH that the speedos are out by? I know that most, if not all are calibrated minus speed, i.e. speedo shows 70mph, but you're doing below that. Also does this change the faster you go? I am curious as I hit a certain speed today (on a private strip) thats somewhat surprised me :evilgrin:
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Offline titchy

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Re: Speedo Clabration
« Reply #1 on: October 28, 2019, 08:28:38 pm »
Legally 2% accuracy if you have a sat nav check it against that
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Offline rich83

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Re: Speedo Clabration
« Reply #2 on: October 28, 2019, 11:32:45 pm »
Mines about 10% out so 77 mph on the clocks gives 70 gps mph. 55mph clock gives 50 gps mph. Roughly.
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Offline LC5F

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Re: Speedo Clabration
« Reply #3 on: November 05, 2019, 08:15:59 pm »
Quote from: titchy on October 28, 2019, 08:28:38 pm
Legally 2% accuracy if you have a sat nav check it against that

That’s a very low margin for error, I heard it was 10%  -speed cameras are set to over 10% +a bit more to allow for this acceptable error

Mine is out by about 10% too - my first vag car to be out by so much
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Offline titchy

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Re: Speedo Clabration
« Reply #4 on: November 05, 2019, 08:32:43 pm »
speed camera rules have changed tightened up 2 people I know got done 34mph in 30 north rd. cardiff
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Offline Stupots

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Re: Speedo Clabration
« Reply #5 on: November 05, 2019, 08:58:16 pm »
Quote from: titchy on November 05, 2019, 08:32:43 pm
speed camera rules have changed tightened up 2 people I know got done 34mph in 30 north rd. cardiff

So 10% + a bit then ;)
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Offline LC5F

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Re: Speedo Clabration
« Reply #6 on: November 05, 2019, 10:18:23 pm »
Quote from: titchy on November 05, 2019, 08:32:43 pm
speed camera rules have changed tightened up 2 people I know got done 34mph in 30 north rd. cardiff

Cough...money grabbers
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Offline pudding

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Re: Speedo Clabration
« Reply #7 on: November 08, 2019, 05:23:16 pm »
It's within 5% at urban speeds but the faster you go, the worse it gets.  I've seen an indicated 130 show as 120 on the GPS,  but that is probably deliberate for forum bragging rights! 

The only way to check it accurately is with a Racelogic GPS unit as it uses much, much better telemetry.  Phones and TomToms are rubbish.  That's why all the car reviewers and race teams use it.
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Offline FJB

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Re: Speedo Clabration
« Reply #8 on: November 08, 2019, 06:45:29 pm »
You can change the coding to be more accurate. I did it with odbeleven, go to dashboard / coding / impulse, change the last 2 digits to 07 (which is maximum), my original coding was 0007403 and I changed it to 0007407. The coding is for changing wheel sizes, I'm on 17s, so it corrected the error. When I'm doing 40 on the gps its 40 on my speedo, 68 on my gps is 70 on my speedo.
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Offline pudding

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Re: Speedo Clabration
« Reply #9 on: November 09, 2019, 11:52:48 am »
Good to know  :happy2:  If it's that accurate up to 70, I think I'm due a ticket in the post soon  :doh:
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Offline probedb

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Re: Speedo Clabration
« Reply #10 on: November 09, 2019, 09:38:22 pm »
Mine is the other way, the wheels should show minor differences but the speedo reads higher than that error according to the GPS speedo on google maps navigation.
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Offline JoshB

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Re: Speedo Calibration
« Reply #11 on: September 26, 2024, 02:49:13 pm »
Just digging this thread back up as I got a speeding ticket the other week on the motorway.
Now I’ve always thought I was tearing passed people on the motorway but just assumed everyone was going steady to preserve mpg…
I’m an old fart so I only potter around anyway so I was pretty surprised when I got clocked at 80mph on the motorway.
So I’ve been to a private road to test my speedo against google maps gps. The results were quite alarming…

Up to 60mph I got the usual VW 10% under, but then over 60, my speedo barely moved. So an indicated 70mph on my clocks and gps says 81mph… at an indicated 80mph gps says 93mph…!!

Like I say, an indicated 55mph and the gps says 50mph, so all good there. Also tested google maps gps against the wife’s car and it was spot on.

Anyone ever heard of the before? It looks like my speedo needle basically slows down after 60mph. I’ll be doing 65 from now on!
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Offline mjmallia

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Re: Speedo Clabration
« Reply #12 on: September 26, 2024, 03:58:37 pm »
The speedo when plugged into VCDS can be adjust for wheel circumferences...........distance impuls number

http://wiki.ross-tech.com/wiki/index.php/VW_Golf_(1K)_Instrument_Cluster


I adjusted mine ages ago, when I went from 17" to 18"

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Offline JoshB

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Re: Speedo Clabration
« Reply #13 on: September 26, 2024, 04:29:58 pm »
Quote from: mjmallia on September 26, 2024, 03:58:37 pm
The speedo when plugged into VCDS can be adjust for wheel circumferences...........distance impuls number

http://wiki.ross-tech.com/wiki/index.php/VW_Golf_(1K)_Instrument_Cluster


I adjusted mine ages ago, when I went from 17" to 18"

But that would compensate for a fixed error, so it would constantly under read by a greater/smaller margin. Mine under-reads 10% as per the manual but only up to 60mph, then it starts over-reading. Also dynamically, as it it doesn’t overread 10%, it’s 5%, then 12%, then 20%…

What I am wondering is if I have the right clocks installed… years ago when R-Tech remapped the car, they commented on the clocks looking different. I guess if they were clocks from a different car, that might explain it…
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Offline JoshB

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Re: Speedo Clabration
« Reply #14 on: September 26, 2024, 04:36:30 pm »


These are my clocks.
« Last Edit: September 26, 2024, 04:39:31 pm by JoshB »
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