GPS/Sat Nav vs. Speedo vs. Speed camera

[hipo1024]

Howdy all!

I was testing out Tom Tom on my phone today. Every car I have ever driven seems to over read on the speedo acording to my sat nav, but only by 2 or 3 MPH at 70. ie. speedo @ 70, sat nav @ 68 ect.

My fronty seems to be over reading by a long way. was doing 70 down the A1(M) and the sat nav said I was only doing 64/65. I desided to drive along side a LGV knowing that he/she would be going full tilt but would also be limmited to 90k, or 56 MPH. My sat nav, both my new Tom Tom and my old NavMan said I was going 55/56 but my speedo said dead 60. So Im guessing that the GPS's are currect and my speedo is well out?? - not really a problem as I'm going to fit some 31s when I get around to doing the arch mod, so that'l cancel out the difference (maybe).

However...What would a speed camera/avg. speed check camera say I was doing? ie. If I desided to ignore the speedo and do 70 according to the sat nav would I get flashed/ticketed? I dont really wont to test it but if these some1 that's in the know that could answer this then great!

Im going to paris for new year, and Ive herd that the french are hot with there speed camera, and that they like hiding them, so I want to be sure of how fast I'm going.

MODs: if this can be moved to a more appropriate place, please do move it.

Regards,
Dan

[Frenchfarmer]

It is all to do with the circumference of the tyres. If you fit bigger tyres your speedo will read slower than you are actually travelling.
If you are driving over here in France and have an accident and you are using non standard wheel/tyre sizes then you better have a cast iron insurance policy.
You also need two red triangles and two fluorescent jackets and a first aid kit.
Failing to go to the aid of a fellow citizen is a no no but I would advise you to just secure the area and deploy your triangles etc. and not get involved in the medical stuff just in case.
Don't forget to let yourself get conned into buying a green card by the "Britain is an Island so you need to pay more to leave it" brigade.
Over here you get a green card with your normal policy.
Good.
But.
If you have a couple of mopeds, that are upstairs in the barn in pieces, that you want to restore one day, they have to be insured Third Party in case someone nicks in and restores them for you during the night and then carries them down a ladder that isn't there and then runs over a little old lady.
Not so good.
Wine's good but.
Hic.

[hipo1024]

[Lee_R]

Morning Dan

OK, this is no more than hearsay, so please don't take this as absolute fact, but...

I have a friend in the diving club who is high up in the highways/motorway maintenance world. He's often involved in work around the area's of average speed checks (M1 improvements around Nottingham was one of his babies) and reckons that from talking to the boys who set them up he knows the score. According to him the cameras are set on actual distance between units (though how they measure this he wasn't sure - probably gps data) and allowed time in transit and thus should read actual (GPS) speed and not speedo speed. They also have a certain margin for error built in - again hearsay but he reckons the guys set them with a 10% extra allowed before they are triggered to register an offence.

Upshot of all this is I've changed the way I drive slightly and haven't been billed yet - I use the GPS on my phone (about 10-15% different to my speedos) and stick to just under that, my logic being that if I ever do get pulled I'll claim I wasn't speeding according to the most accurate measuring device I have, and ask them to prove I was.

Lee

[pinotera]

i'd go on the speed from car speedo,my sat nav does the same its diff to the car.Don't think it would stand up if pulled over for speeding,going by what the sat nav was telling you.You'd only need to be pulled by a jobsworth copper

[Road Hog]

When I visited France if you got caught on a fixed speed camera you would need to be blind,they are huge & so were the warning signs,even the only hand held I saw in three weeks (granted it was on a corner & they were in the drive of a private house,so not where you expect them to be) was obvious,not only were the officers visible their car was as well

[jimmybhoy]

Speed traps (uk) allow for 10% speedometer inaccuracy. I have often driven 77 on motorway with police behind me, It is all down to the wheel/ tyre size, i changed the wheels on a porsche turbo i owned from 16" to 17", it was slightly slower off the mark, and my speedo was all over the place, slower than the speedo indicated. As i drove a little close to the knuckle, i was uncertain if sat nav or speedo was accurate. I used the roadside smiley face thing to get speed then checked it with satnav/speedo. It was spot on with the sat nav, therefore i adjusted my speed accordingly rather than get speedo calibrated. More money for petrol /mods & beer tokens

[RatCav]

I did hear once that someone got charged with speeding and used his satnav speed reading as evidence to get let off. How successful anyone else would be I don't know. Will ask a few questions to some more legally proficient friends of mine.

[rancidrich]

I use gps/sat nav for my speed,i think it's more reliable than the mechanical speedo plus my speedo packed up months ago and i cant be bothered to fix it

[country_Est]

I have 2 sets of tyres, 265 75 16 MT's and 245 65 16 AT,s and have tried these with 2 sat navs, With the MT's the speedo reads spot on with the sat nav, and the at's read about 5 mph Higher on the speedo than sat nav @70MPH

Trev

[hipo1024]

[dave1966]

Hi all.

I hired a 2010 transit van a couple of weeks ago and my sat nav was giving me different speed's
to the van's speedo. One minute the speedo on the van was 70 but my sat nav said 64/65,it's not
just our Fronty's that it happens with.

[hipo1024]

[dave1966]

Some people are lucky. Im going to stick with my speedo but I dont speed these days though but I dont crawl
along the roads though.

[jimmybhoy]

[/quote] My mates mum (same mate by the way) has been flashed loads of times [/quote]
.....I Hope she reported them!!