speedo accuracy

**robtt09** · 01-07-2009,10:52 AM

Very impressed with accuracy of speedo on my car! According to my Snooper Sapphire it overreads by only 1mph at 80mph!That is on a straight and flat A road so believe the Sapphire will be accurate.

**Plife** · 01-07-2009,11:53 AM

Yes come to the same conclusion against my Sat Nav. Guess that is pretty accurate.

**ScottyUK** · 01-07-2009,12:04 PM

That's good news. I've yet to try it yet. I've heard that somewhere in MMI you can display the GPS speed if you have SatNav but I haven't done this yet.

My B6 S4 was showing 164 on the dash which exactly matched the electronic speed trap.

**A1287210** · 01-07-2009,05:51 PM

I posted a little message about this a while back saying that I found that even going at bang on 50 mph through the roadworks I seemed to be flying past everyone. Maybe very accurate. I would be very interested in the GPS speed. I'm just waiting for a stretch of road when I can really stretch the legs of the 143..cos the speedo says I goes up to 180 mph

**rd1** · 01-07-2009,07:32 PM

I found that my speedo is under reading by 2mph compared to my Novus Rider cam spotter. I also found that I was always overtaken through the average cams when on cruise.
I would be interested to know how to turn on the MMI GPS if poss as this would check the novus out as well.
Roger

**A1287210** · 01-07-2009,10:27 PM

I think that it may be a myth,,,,,,

**Red 2** · 02-07-2009,05:47 AM

My reading is within 1mph of the TomTom's speed reading at motorway speeds.

Compare that to our Golf which overstates the speed by circa 9%.

**mkc** · 02-07-2009,09:51 PM

I think they are pretty accurate. On the M4 there are plenty of 50mph speed traps and average speed traps. At 48/50 on the DIS I was going past everyone

Bratty · 03-07-2009,10:09 AM

I think that the accuracy of your speedometer is academic, it changes with the rolling circumference of your tyres, therefore when your tyres are new they are big and when they are worn they are ever so slightly smaller. Also the difference between the diameter and aspect ratio from the range of available tyre and wheel combos makes a huge difference. Hence the tolerance allowed in speedo inaccuracy by the police.

Dunk?(perhaps it is possible through vag-com to re-calibrate but I doubt it, some car manufacturers allow you to adjust the accuracy of your MPG?)

**Jop** · 03-07-2009,10:45 AM

The speed on my dis differs slightly to what the actual speedo says.

for example. if my dis is saying 50, the speedo says 51-53, not sure exactly what. the needle is slightly but noticeably above the 50 mark.