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Discussion Starter #1
I've noticed with the proliferation of those irritating radar smiley speedo signs - the ones that give you speed readout and a :) if you are 30 or below and a :( if you are over 30 - that my speedo is reading fast.

It's not just one of these signs, but it's quite consistent. If I'm doing about 30 on my speedo, then the signs say 26-27, and today I approached one with 34 on the clock and it gave me a nice big smile with 30 mph.

Anyone done any sort of checks on their speedo?
 

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Vish mine does the same I think all manufacturers make their speedo's read fast, I saw an article in some car mag (Max Power, Fast Car, etc., etc.) where they tested a few cars through timing lights and they all read fast then they put larger tyres on and run them through again and they were all pretty much accurate. :rolleyes:
 
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Discussion Starter #3
Not seen one of these...wierd by the sound of it :D ...what size tyres you running?

wrinx
 

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On my Super the speedo ran a bit high but on the Q4 its dead on, I judge it by a PDA GPS system which gives absolute perfect readings apparently! :eek: :)
 

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I got 73mph on a GPS with 80mph indicated on the clock, so I'm guessing it reads about 10% fast, but not sure if that's consistent across the range. :confused:
 
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Jason77's speedo read 125mph on the way to Keswick on the M6, the GPS system read 124mph, so his speedo is accurate.
 

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Generally speedometer accuracy is plus 10% so in theory it will never show your doing a lower speed than the actual. Accuracy is tested with the original equipment fit of tyres by the manufacturer (usually two tyre suppliers are used per type of vehicle). Tyre tollerances on rolling diameter can mmake a slight difference but can usually be ignored.

So 33to33 at 30mph

70to77 at 70mph

some speedo dials have small markings that indicate the settings used when calibrating the units.
 

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I've seen 17mph on the 'Smiler' when I was virtually stationary, but that was after heavy braking, which probably confused it.
What narks me is the sour look they give you at a mere 31mph. Having said that, those things are infinitely preferable to a gatso.
 
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Discussion Starter #9
wrinx said:
Not seen one of these...wierd by the sound of it :D ...what size tyres you running?

wrinx
205/16 x 45 (on plasticine speedlines :rolleyes: )
 
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The 45's do make the speedo over read a little but not 2 or 3mph.....apparantly 60 would read as 60.5..woohoo :rolleyes:

wrinx
 
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