MK5 Golf GTI

All Things Mk5 => Mk5 General Area => Topic started by: Northy1985 on September 20, 2015, 06:01:43 pm

Title: Speedo reading wrong
Post by: Northy1985 on September 20, 2015, 06:01:43 pm
Does anyone know how I can correct my speedo. Doing 70mph yet clock is reading 80 I know this as I followed my brother on motorway he was doing 70 mine 80. And also wen clock reads 30 I'm doing 28. 40 is 36. 50 is 45 and so on
Title: Re: Speedo reading wrong
Post by: doylebros on September 20, 2015, 06:20:46 pm
I've never done this but these recon it's simple http://forums.tdiclub.com/showthread.php?t=158652
Title: Re: Speedo reading wrong
Post by: Northy1985 on September 20, 2015, 06:54:25 pm
I will give it a go it just seems weirdest sits on zero wen off and 30 is not too bad but every 10mph extra adds like 2mph so by time I doing 80 it's close to 70
Title: Re: Speedo reading wrong
Post by: dazza on September 20, 2015, 07:03:52 pm
This was at the end of that thread. Supposedly you can adjust with VCDS.

http://www.myturbodiesel.com/wiki/speedometer-fast-error-adjustment-and-correction-mk5-mk6/
Title: Re: Speedo reading wrong
Post by: Northy1985 on September 20, 2015, 07:58:51 pm
Looks too complicated to me lol. I don't have vcds either.
Title: Re: Speedo reading wrong
Post by: dazza on September 20, 2015, 08:13:54 pm
Have a look at the VCDS register i'm sure someone can help for a few beer tokens.
Title: Re: Speedo reading wrong
Post by: Northy1985 on September 20, 2015, 08:18:42 pm
Yes mate I will do cheers
Title: Re: Speedo reading wrong
Post by: Carpy25 on September 20, 2015, 09:12:50 pm
Do the simple things first are you running the correct size tyres ,are they at the correct pressure , smaller tyres or low pressure will make the speedo under read
All speedos under read but yours is outside the 10% allowed

Rob
Title: Re: Speedo reading wrong
Post by: Northy1985 on September 20, 2015, 09:27:15 pm
I'm running 18" wheel with 215/35/18 tyre with 28 psi. Only reason I noticed it was today traveling with the Tom Tom on I was doing 80 but that was reading 74 but my brother following said I was doing 70. So I dropped down to my speedo 70 and he said was just over 60.
Title: Re: Speedo reading wrong
Post by: Carpy25 on September 20, 2015, 09:37:42 pm
Your tyre size is down and your pressure is lower than recommend every  revolution less distance will be covered but your reading higher than the speedo  if I'm reading this right

Is your car meant to have 18 " wheels with 225 40 18 tyres or something else as standard

Rob
Title: Re: Speedo reading wrong
Post by: Carpy25 on September 20, 2015, 09:43:23 pm
Try this

http://www.wheelcalc.com/

To compare what should be fitted to what you have fitted pressure will play a small part but not hugely


Next do yo have to correct gear box fitted , have you the correct clocks fitted

Rob
Title: Re: Speedo reading wrong
Post by: Northy1985 on September 20, 2015, 10:06:00 pm
As far as I know all the clocks etc are correct and the wheels where 18" Monza with 225/40/18. Yeah I am reading higher than I am actually going. The Tom Tom reading 74 car reads 80 but at 30 I'm doing 28 and to every extra 10mph I'm losing 2mph so by 80 I have nearly lost 10mph
Title: Re: Speedo reading wrong
Post by: Carpy25 on September 20, 2015, 10:29:15 pm
With the tyres your running using the web site I posted you should be reading about four MPH over so your about 14 MPH out
Think you've covered the easy answers  must be a set up problem as said above  vagcom is your next step I think

Rob
Title: Re: Speedo reading wrong
Post by: Northy1985 on September 20, 2015, 10:33:28 pm
I still have the standard wheels so I may aswell try with these just to rule out wheels/tyres problem then I know for sure. Then go from their
Title: Re: Speedo reading wrong
Post by: xjay1337 on September 20, 2015, 11:00:28 pm
Reallly over complicating things here loll
The car is fine.
Speed differences are due to tyres/rolling diameter/vcds coding values (some GTI's were off so need changing on vagcom).
Title: Re: Speedo reading wrong
Post by: dronners on September 20, 2015, 11:32:28 pm
consider it a good anti speeding assistant  :happy2:
Title: Re: Speedo reading wrong
Post by: Scottymon on September 21, 2015, 12:18:10 am
I thought Most cars dials were ~10% out when comparing to the Actual speed.

Title: Re: Speedo reading wrong
Post by: Northy1985 on September 21, 2015, 07:21:18 am
Reallly over complicating things here loll
The car is fine.
Speed differences are due to tyres/rolling diameter/vcds coding values (some GTI's were off so need changing on vagcom).
Only thing different on mine is the fact front tyres are 215/35/18 rather than the 225/40 standard other than thats car is fine i think the difference is not as bad as my bro said as today i sat at 70 and navigation read 65 then at 80 was 75ish at 30 it reads 28
Title: Re: Speedo reading wrong
Post by: Rossimac on September 21, 2015, 08:45:24 am
I moved from standard 17" Monzas to 18" Pescaras. Using a 225/40/18 all around, I noticed too that the speedo was out quite badly.

I got my VCDS and started to adjust the Digital Impulse Number. All settings yielded no difference. Still reading high!
Title: Re: Speedo reading wrong
Post by: Northy1985 on September 21, 2015, 09:17:58 am
Am i just better off leaving it and just stop being a pussy and getting on with it or just change front tyres back to 225/40
Title: Re: Speedo reading wrong
Post by: xjay1337 on September 21, 2015, 10:05:13 am
Reallly over complicating things here loll
The car is fine.
Speed differences are due to tyres/rolling diameter/vcds coding values (some GTI's were off so need changing on vagcom).
Only thing different on mine is the fact front tyres are 215/35/18 rather than the 225/40 standard other than thats car is fine i think the difference is not as bad as my bro said as today i sat at 70 and navigation read 65 then at 80 was 75ish at 30 it reads 28

Well you have changed the rotational diameter of the wheels so of course it would be different.
Your car speedometer is never going to be 100% accurate..
Title: Re: Speedo reading wrong
Post by: Northy1985 on September 21, 2015, 11:42:43 am
I am going to put standard wheels back on and do another test run and see if it goes back to normal ish and then go from there. Only good factor is cant get caught by speed camera
Title: Re: Speedo reading wrong
Post by: Scottymon on September 21, 2015, 12:06:08 pm
Going from:

225 40 18
to
215 35 18

Creates a -4.55% difference in the roll (-29mm)

http://www.tyresave.co.uk/tyresize.html

Coupled with the fact most speedo's are incorrect, usually around 10% I've found, when comparing to the Sat Nav.
Title: Re: Speedo reading wrong
Post by: Northy1985 on September 23, 2015, 07:18:47 am
Another run today and at 80 on clock is 74 on navigation and gps speed 70 is 65 and at 60 is 56. Faster you go the more it goes out 90 is 82
Title: Re: Speedo reading wrong
Post by: xjay1337 on September 23, 2015, 09:39:23 am
Another run today and at 80 on clock is 74 on navigation and gps speed 70 is 65 and at 60 is 56. Faster you go the more it goes out 90 is 82

It's fine!!!!!
Title: Re: Speedo reading wrong
Post by: Northy1985 on September 23, 2015, 10:05:25 am
Another run today and at 80 on clock is 74 on navigation and gps speed 70 is 65 and at 60 is 56. Faster you go the more it goes out 90 is 82
So stop being a pussy then lol
It's fine!!!!!
Title: Re: Speedo reading wrong
Post by: Carpy25 on September 23, 2015, 06:54:21 pm
Another run today and at 80 on clock is 74 on navigation and gps speed 70 is 65 and at 60 is 56. Faster you go the more it goes out 90 is 82

that about right its under the 10% so don't worry  :drinking:

Rob
Title: Re: Speedo reading wrong
Post by: Northy1985 on September 23, 2015, 07:47:46 pm
Another run today and at 80 on clock is 74 on navigation and gps speed 70 is 65 and at 60 is 56. Faster you go the more it goes out 90 is 82

that about right its under the 10% so don't worry  :drinking:

Rob
I will just go with it for now and maybe try standard size tyres to see if it helps but I'm glad I sort of know it's normal ish  :happy2: