[WURZEL]

I travel through a 50mph roadworks which show 50mph on my Ceed and 55mph on a Golf when compared to the readings on Tomtom. I always stick to the satellite speed of 50mph. I would assume the Ceed is giving a more accurate result? Secondly, how does this affect stated mpg of such vehicles if the Golf is measuring different miles to a Ceed? Is it down to wheel size? Would like some views on this topic.

 

[RTFishall]

I travel through a 50mph roadworks which show 50mph on my Ceed and 55mph on a Golf when compared to the readings on Tomtom. I always stick to the satellite speed of 50mph. I would assume the Ceed is giving a more accurate result? Secondly, how does this affect stated mpg of such vehicles if the Golf is measuring different miles to a Ceed? Is it down to wheel size? Would like some views on this topic.

The speed shown on the TomTom will always lag behind the true speed because of the limited true accuracy of Sat Navs and the time it takes to process the data. As far as the accuracy of the speedo, this can also vary. It's inaccuracy also increases with higher speeds.
Fitting larger (or smaller) diameter tyres (wheels) than that fitted as standard will also cause errors.
This is why the police generally allow a small amount over the speed restriction in force. The only really accurate measure would be with the use of radar or laser ranging equipment and as far as I understand even Rolls Royce have not fitted that to their cars yet!

 

[WURZEL]

The speed shown on the TomTom will always lag behind the true speed because of the limited true accuracy of Sat Navs and the time it takes to process the data. As far as the accuracy of the speedo, this can also vary. It's inaccuracy also increases with higher speeds.
Fitting larger (or smaller) diameter tyres (wheels) than that fitted as standard will also cause errors.
This is why the police generally allow a small amount over the speed restriction in force. The only really accurate measure would be with the use of radar or laser ranging equipment and as far as I understand even Rolls Royce have not fitted that to their cars yet!

Yes...got done for driving at 38mph in 30mph zone, picked up fine and penalty points. Seems like it was not a 'small amount' over the limit. However, put it down to experience or lack of it.

 

[dubster]

That small ammount is generally known to be 10%.
You should get away with 33 in a 30 zone. Of course, who's to say your speedo is accurate enough to know you're actually doing 33mph!
So anything above 77 on motorways is a ticket, where most 'normal conditions' motorway driving seems to hang around the 80 mark

Your 38 is well into the ticket margin, though I wouldn't wish points & fine on anybody.

Wasn't you offered a 'speed awareness course' instead of points?

 

[WURZEL]

Yes, was offered a speed awareness course down in Somerset where offence was committed. Now, that's over 250 miles or so from my home in Yorkshire. Not sure if they could have transferred the course to N.Yorkshire. Just took the easiest option at the time I suppose.

 

[wizypuss]

2011 ceed sw2 speedo is three miles off on the slow side. town speed warning sign said I was doing 27 when speedo said 30