TT Indicated MPH

zaffy · Posted: Sat Feb 07, 2009 4:12 pm Post subject: TT Indicated MPH

Does anyone know how acurate the MPH read out is on a TomTom. I have just changed cars and found that my TomTom indicated MPH compared to that of my car at 30mph, reads 3mph slower, (TT 27 - Car 30),it was the same with my previous car. At 60 it indicates 56.

mikealder · Posted: Sat Feb 07, 2009 4:16 pm Post subject:

Welcome to the forum, your GPS speed reading is the one that is accurate, a car speedo is often out by around 10% - Mike

EricWB · Frequent Visitor Joined: Jan 31, 2007 Posts: 310

Construction and use regulations for cars require that any error in the speedometer must be positive, that way you will never be able to use the excuse that your speedometer only showed 30 when you get stopped for 35. I think manufacturers seem to take full advantage of the 10% maximum allowed either to make owners think their car can go faster than the makers claim, or just to help prevent prosecutions.

mcwarre · Regular Visitor Joined: Mar 25, 2004 Posts: 157

zaffy · Posted: Sat Feb 07, 2009 8:31 pm Post subject:

So going with that principal, my car has clocked up less miles than is shown on the odometer.

Pocketgps · Posted: Sat Feb 07, 2009 8:52 pm Post subject:

classy56 · Posted: Sun Feb 08, 2009 1:09 am Post subject:

zaffy · Posted: Sun Feb 08, 2009 2:26 am Post subject:

I didn't mention speedometer, I said odometer, in case you are not aware, thats the row of numbers that tell you how far you have travelled

trevor.dowle · Lifetime Member Joined: 16/06/2003 05:22:14 Posts: 412

zaffy · Posted: Sun Feb 08, 2009 8:38 am Post subject:

Sorry, misunderstood the reply.

Andy_P · Posted: Sun Feb 08, 2009 3:15 pm Post subject:

So, quick answer... trust the SatNav to be more accurate then the car.

dhn · Posted: Sun Feb 08, 2009 3:28 pm Post subject:

Wasn't there a thread here about a year ago that went on for about a million pages on the same topic?
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David

Mullet · Frequent Visitor Joined: Dec 12, 2005 Posts: 1051

Old recurring chestnut, along with :-anyone used a TomTom on an aircraft? and how can I time a standing quarter?

Andy_P · Posted: Sun Feb 08, 2009 4:11 pm Post subject:

navver · Posted: Tue Feb 10, 2009 9:12 pm Post subject:

The odometer is out by a similar amount as my speedometer in my 406.

Before I got a satnav I tried an autoroute route and followed the trip odometer readings to prompt me for each turn. By the time I got to London (100miles) I was several miles adrift.

The fuel consumption on the trip computer is also out by a similar amount compared with brimming the tank & working it out from the odometer.

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