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Thread: Speedo / GPS speed....

  
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    Speedo / GPS speed....

    Seen a lot of threads recently where loads of people go on about 'well your speedo WILL be 10% out' blah blah blah

    I just wondered why people say this as fact. Sure, speedos may have some sort of build tolerance and speed cameras will no doubt have a tolerance to allow for this but think its wrong to assume ALL speedos are 'wrong'.

    eg. Using Sat Nav and Origin my old Mk3 speedo read 70 whilst whilst the GPS was about 67, HOWEVER my 2.2 coupe reads 70 MPH and the same sat nav reads 70 occasionally flicking to 69 for a second then back again.

    Just wondered if there was anyone actually 'in the know' or wondered what other members experiences were with their Sat Navs / speedos?

    (soz for the long post! )

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    most speedos are fairly accurate up to the legal limit and within the tolerances of the majority of speed cameras to allow for this. However, the faster u go the less accurate things become. Personally my speedo on my 1.6 is very accurate compared with GPS (obviously GPS has a 1/2 second delay) but at a steady speed all seems pretty much perfect. Upto approx 95mph its spot on - 95-105 is where it starts to over read but then again whats the point IMHO 70 is the limit and thats for a reason! Anyway - thats another matter!
    Personally I think the "10%" quote relates to illegal speeds when things are less accurate. 10% on a 70mph figure would be incorrect...and I guess it's just been taken out of context.
    I would also say that most ppl will not say "speedos are wrong" its generally those who arent really upto speed (mind the pun) and have just heard snippets of info about the 10% figure and presume this is the case for any given speed.

    Anyway just my thoughts on it all so Im sure not everyone agrees (as per a lot of my posts of late!) so feel free to discuss to ur hearts content!!!

    And u thought ur post was long!

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    its gonna be way out when you put huge wheels on the car. Still debating which 18s are going on my car, but whichever i choose i will need to bring it to vauxhall and get them to adjust the speedo correctly

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    vauxhall will adjust the speedo with new rims? how much do they charge for that service?


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    i have no idea, i just heard about it

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    Quote Originally Posted by AZZA
    its gonna be way out when you put huge wheels on the car. Still debating which 18s are going on my car, but whichever i choose i will need to bring it to vauxhall and get them to adjust the speedo correctly
    By fitting 215/35/19's to mine it made it more accurate.

    Its pretty much spot on with my GPS

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    Quote Originally Posted by AZZA
    its gonna be way out when you put huge wheels on the car.
    thats absolute rubbish - I and several others have even told u in one of your many previous threads that as long as u stick with known tyre sizes then speedo accuracy is not a problem. In a lot of cases (mine included) fitting oversized rims makes the speedo even more accurate. I went from 14" steels to 18" alloys and its spot on now.

    Anyway,,,what exactly do u define as "huge wheels" are u talkin tim westwood wannabe gangsta style 22" rims or just normal run of the mill 18s????

    Its statements like yours which have led ppl to create threads like these!

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    Quote Originally Posted by GeordieBandit
    thats absolute rubbish - I and several others have even told u in one of your many previous threads that as long as u stick with known tyre sizes then speedo accuracy is not a problem. In a lot of cases (mine included) fitting oversized rims makes the speedo even more accurate. I went from 14" steels to 18" alloys and its spot on now.

    Anyway,,,what exactly do u define as "huge wheels" are u talkin tim westwood wannabe gangsta style 22" rims or just normal run of the mill 18s????

    Its statements like yours which have led ppl to create threads like these!
    calm down mate - you seem to be shouting at me an awful lot lately...

    im putting 225/40/18 on my car, its gonna knock the speedo out. With the amount of speed cameras in NI, im gonna have to do something about it

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    how do you know azza?

    if you fit the recommeded tyre size for the car it will be fine, and if it is knocked out it not gonna be a few mph out, its not like its gonna read 20mph when your actually doing 50
    Now has a clio - dont ban me

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    hey mate - he's been told time and time again that this isnt strictly the case but judging by this thread he's pretty determined its gonna be 'miles out' FFS the width & profile he's gonna be using aint gonna cause massive differences as u pointed out but some ppl just wont take things at face value.

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