Speedo Adjustment

[icepassat]

Hi all,
I have a 2011 Passat Highline and the speedo reads 6klms/hr more than I'm actually travelling (GPS used). My question is can the dealer adjust it or is there another way of adjusting it?
The car is stock standard with standard wheels and tyres, its a pain constantly checking and adjusting the cruise thinking maybe it is right but when I check with the GPS its constantly 6klms fast.

[revivor]

Mine is about 7km/h.

Read this!
Speedo Accuracy | Motoring | RACQ

[Cossor]

My car is MY13, Came with sat nav. Very little use for it, but would like to know how to measure speed
using this device. As it is, I simply adjust cruise control for 114 or 103 KPH depending on road.
However, I understand unless one has access to special computer software, the average service technician cannot adjust.

[booba]

you can adjust using vcds, there is a correction factor adjustment for speedo. apply special firmware to nav to enable secret menu that will show can bus speedo with the correct speed.

Here is a link, should work on passat however i haven't tried. I have Premium MFD so even if it worked then it might not work on non premium MFA.

Speedometer fast error adjustment and correction - mk5, mk6 | VW TDI forum, Audi, Porsche, and Chevy Cruze diesel forum

[brad]

6kph is about right. My Octavia was 10kph out.

I've fitted progressively bigger diameter tyres over the years (went from 205/55r16 to 235/45r17 to 225/55r16 to 225/50r17) to the point where 1=1. It's a primitive way to fix the problem and the diameter increase i've made is probably illegal I like it.

[ozynigma]

^^ 15mm increase is allowable under the national code of practice for vehicle modification. That should give you 3 or 4% increase on a normal road tyre and decrease speedo over read error by the same percentage. 10% is a lot taller wheel/tyre and you could run into other issues with clearances and rubbing.

[icepassat]

Thanks all, good to know I'm not the only one, but it sucks!

[brad]

^^ 15mm increase is allowable under the national code of practice for vehicle modification. That should give you 3 or 4% increase on a normal road tyre and decrease speedo over read error by the same percentage. 10% is a lot taller wheel/tyre and you could run into other issues with clearances and rubbing.

Yep, your right.
I've gone +25mm on diameter (+4%) and the tyres have quite a square section shoulder. My car is lowered about 40mm & if I really hook into a corner & hit a bump halfway through there's a slight touch up front (guard liner I think). If it was factory height it wouldn't be an issue.

+22mm (+3.5%) with a rounded shoulder doesn't have clearance issues with the 40mm drop so there isn't much in it.

[Amalgam]

6kph is about right. My Octavia was 10kph out.

I've fitted progressively bigger diameter tyres over the years (went from 205/55r16 to 235/45r17 to 225/55r16 to 225/50r17) to the point where 1=1. It's a primitive way to fix the problem and the diameter increase i've made is probably illegal I like it.

+ 1

I did the same with my Evo X when it was time to replace my tyres. My local Bob Jane was very helpful. We went up one tyre width while retaining the same section and it brought the difference down to 0 calibrated against the GPS.

Have a look at

Object moved

All these combinations are legal.

245/45/17 or 255/45/17 should work. You just need to do the maths.

[Ryan_R]

Installing a PolarFIS is one of the best ways I've found to get a more accurate speedo on the dash. (Out by 2% instead of 8% for me)

[brad]

+ 1

I did the same with my Evo X when it was time to replace my tyres. My local Bob Jane was very helpful. We went up one tyre width while retaining the same section and it brought the difference down to 0 calibrated against the GPS.

Have a look at

Object moved

All these combinations are legal.

245/45/17 or 255/45/17 should work. You just need to do the maths.

245/45r17 will be really baggy on the usual 7.5" rims most VWs have. Recommended rim is 7.5-9". If nothing else the ride would be very plush.

255/45r17 is minimum 8" rim.

Basically, to fix the issue properly yo have to fit an illegal diameter tyre size, which most people aren't willing to do.

You will get reasonably close (for most people) if you increase diameter by a legal amount & have a fiddle with the correction factor via vcds.