Skoda Speedometer or Garmin Speed Reading?

[bluckaneyr]

I have noticed that there is always a difference between the speed information I'm getting from my Skoda Fabia Combi speedometer and the readings from my Garmin Nuvi 1490.

Typical examples would be-

1) Fabia speedo - 80 km/p/hr - Garmin 77 km/p/hr

2) Fabia speedo - 120 km/p/hr - Garmin 116 km/p/hr.

Can anyone advise on which information is the most accurate, please.

[aubrey]

The sat-nav is the accurate one. Car speedos read high so they err on the side of caution with sticking to the speed limits.

No manufacturer wants a court case where a speeding fine was challenged because of the speedo telling the driver they were within the speed limit.

[BigV]

As above. Speedo only accurate to within 10% and always err on high side. Sat Nav should be quite accurate as it relies on positional information not variable wheelspeed. Some concept cars out there have speedo's based on GPS info. Probably only a matter of time before it becomes standard on all cars.

[Can]

Comercial GPS recievers are not actually that accurate for possitioning, however as has been said they are more accurate than most car speedo's for velocity measurement. Also I believe the EU have added some rule that speedos must read a certain amount over.

[lol-lol]

I have noticed that there is always a difference between the speed information I'm getting from my Skoda Fabia Combi speedometer and the readings from my Garmin Nuvi 1490.

Typical examples would be-

1) Fabia speedo - 80 km/p/hr - Garmin 77 km/p/hr

2) Fabia speedo - 120 km/p/hr - Garmin 116 km/p/hr.

Can anyone advise on which information is the most accurate, please.

Vehicle manufacturers are allowed 10% accuracy on speedometers but this actually translates to a 12.2% (10 and 2% compounded) as they are allowed a further 2% for variations in tyre size rolling circumference due to different tyre size options on the vehicle.

Manufacturers seem to deliberly pitch there speedo about 5% over reading as this is the safer thing to do and might make people think their vehicles are faster than they actually are. Italian and Japanese speedos in the 1970s were routinely 10% or even more over reading, probably sold thousands of extra vehicles because of it where Britain was trying to make the most acurate speedo it could.

So sat nav probably around 1 or 2% accurate to actual and the car 5% over reading. In the UK speed traps are normal set at around 10% plus a couple of MPH but that could be zero, one, two, three or four mph and there are reliable stories about people getting done for 33 in a 30 etc so best stay true on the the sat nav speed and do not use all of the tolerance and only in perfect conditions and with vehicle in good condition to.

With the price of fuel in Ireland, VAT at 23% can many afford to go quick? Or you can come and buy your fuel at Asda Eniskillen which is now the 6th busiest Walmart store in the world with people from the 26 counties buying fuel in the 6 counties. Makes a change from all the traffic going the other way for all the years before 2007/8 when the EUR/GBP when from 60p to 90p!

Edited 4 February, 2012 by lol

[Moist Von Lipwig]

GPS as has been said is going to give a more accurate reading, but remember it's errors could mean it reads low. Car speedo's are set to deliberately read high. The accuracy will also depend on the quality of your device and it's update frequency. I find my sat nav updates quickly but the torque app and obd device is slow and while accelerating, even gently will lag behind the speedo, once steady it will catch up.

The only way to really check the accuracy is by running over a set distance and doing some sums. The police used and may still use this method to check the callibration of their in car systems.

You could always run through a speed trap then ask for the picture to check the speed but this might be a bit of an extreme and expensive method!

[GeneralPurpose]

My motorcycle speedos generally are 10% high with their readings according to my gps. Car is prolly the same. Got told by one of my traffic cop bro in laws you can go over limit (accidentally of course) by 10% and a further 2mph and still be ok in theory. So in a 30 limit you can do 35mph through a radar or speed camera and still be ok, but 36 is a hit and you get done. This is prolly why my lil sis got done for 36 in a 30 limit through a camera. She took the speed awareness course and avoided points but got a fine of course. She doesn't normally speed but we were all on our way to be with dad who had taken a turn for the worse in hospital and later that morning passed away, I guess she was a bit pre-occupied which in itself is not good.

[bluckaneyr]

Many thanks to Aubrey, BigV, Can, lol, gjlb and Estate Man for your informative responses.

Here in Ireland I don't think we get the benefit of a 10% margin of forgiveness.

We seem to get a flat margin of 3km/p/hr, so you could be equally at risk going at either 33 km per hr in a 30 limit or going over 103 km/per/hr where the limit is 100.

As for the comments on the level of taxation that has been introduced onto our petrol prices, I fear there's worse to come. The government know the motorist is a sitting duck target for mugging.

[lol-lol]

Many thanks to Aubrey, BigV, Can, lol, gjlb and Estate Man for your informative responses.

Here in Ireland I don't think we get the benefit of a 10% margin of forgiveness.

We seem to get a flat margin of 3km/p/hr, so you could be equally at risk going at either 33 km per hr in a 30 limit or going over 103 km/per/hr where the limit is 100.

As for the comments on the level of taxation that has been introduced onto our petrol prices, I fear there's worse to come. The government know the motorist is a sitting duck target for mugging.

Yes although the tolerence is of course EU wide the authorities can say well you should know that such analogue instruments are inherently inaccurate and therefore the driver should make allowance ie if not calerbrated then travel at 10% or so below to make sure they stay within the law.

As to MPG and buying fuel it is a tough one. It is a bit far for you in Dublin to go up to the six counties to buy fuel. It always use to amuse me have Loyalist taxi drivers going to buy fuel in the South, even filling barrels with the cheaper Diesel.

There is loads of info on hyper-miling. Often buying fuel and not filling up totally. Carrying less weight in th car, free-wheeling, especially with DSG, really helps consumption. Winter tyres some say and it all helps the planet.

Ireland needs the EU to further lower its exchange rate with GBP/USD and Irish people to move abroad and send money home just as it has been for centuries plus the EU needs to pay for better transport links such as a tunnel from Stranraer to Ireland!

Edited 6 February, 2012 by lol

[bluckaneyr]

lol wrote-

It is a bit far for you in Dublin to go up to the six counties to buy fuel. It always use to amuse me have Loyalist taxi drivers going to buy fuel in the South, even filling barrels with the cheaper Diesel.

Thanks for the response, lol.

Any day now fuel will be as plentiful as water around here. Then it will be all about bigger cars and more speed....... otherwise we will be up to our knees in fuel.

http://www.irishtimes.com/newspaper/ireland/2012/0126/1224310758814.html

http://www.irishcentral.com/news/Natural-Gas-find-in-Leitrim-hills-could-be-worth-up-to-55billion-138472574.html

[lol-lol]

lol wrote-

It is a bit far for you in Dublin to go up to the six counties to buy fuel. It always use to amuse me have Loyalist taxi drivers going to buy fuel in the South, even filling barrels with the cheaper Diesel.

Thanks for the response, lol.

Any day now fuel will be as plentiful as water around here. Then it will be all about bigger cars and more speed....... otherwise we will be up to our knees in fuel.

http://www.irishtimes.com/newspaper/ireland/2012/0126/1224310758814.html

http://www.irishcentral.com/news/Natural-Gas-find-in-Leitrim-hills-could-be-worth-up-to-55billion-138472574.html

Yes there is reckoned to be oil and gas in the Celtic and Irish Sea as well as drilling on land.

Ireland, Wales and South-West England, North West England could all have tens of billions of Euros/GBPs of reserves. North Sea oil has kept Britian going for years and oil and gas could still be our salvation. We will still have expensive fuel prices as we need to sell as much as possible to the Chinese to pay for everything else we want.

Edited 7 February, 2012 by lol

[delta925]

I'll stand corrected but I thought that the UK legal requirement, set many years ago when speedometers were simpler mechanical units rather than electronic and manufacturing tolerances much greater, was that beyond a certain speed they must not under read or over read by more than 10%.

Hence manufacturers aim in the middle so 5% high is normal.

The accuracy of your Garmin ought to be within 1%

[lol-lol]

I'll stand corrected but I thought that the UK legal requirement, set many years ago when speedometers were simpler mechanical units rather than electronic and manufacturing tolerances much greater, was that beyond a certain speed they must not under read or over read by more than 10%.

Hence manufacturers aim in the middle so 5% high is normal.

The accuracy of your Garmin ought to be within 1%

Do not think there is anything of this nature that is a UK requirement but this now falls to being an EU requirement as this is the largely forgotten aspect of the EU in that part of the economies of scale is that the specification of goods for the half billion people who live in the EU is the same ie to the "CE" level.

So if analogue speedos are made to 10% accuracy then this would be an EU requirement whether the cars are make in the EU for the EU market or outside the EU for the EU market.

What is interest is the digital speedos like the Kms/hr one we have in the UK spec Skodas. Is the speedo shown on the dial 62% of that shown in the digital KM/hr display or to what error?

Also interesting that the digital speedo on my motor bikes, which are digital, are also 5-10% over-reading. How can this be deliberly so inaccurate? It simply has to count the front wheel revs based on a tyre warn down to the legal minimum etc, possibly a bit flat, and so only add about 2% or so for a safe margin.

Use the Sat Nav speed but do not go over 10% of the nomimal speed limit in the UK and not even that in other foreign countries as although the car have the same manufacturing tolerances police forces work to differ rules it appears!

Edited 9 February, 2012 by lol

[Igloo Vindaloo]

My lovely old Citroen C3 had a digital speedo. It was impossible to get it to read any speed between 0 and 6 km/h.

It read 5km/h over the GPS at all speeds.