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Discussion Starter #1
Recently got a 2.5 TDI T5 which came on 20" alloys, due to the bigger circumference the speedo is reading around 4/5mph slower than the van is actually travelling.

I was wondering if anyone could offer some insight as to weather there's somehow a way to recalibrate the speedo and would it be cheaper than just getting a smaller set of wheels?

Cheers!
 

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Discussion Starter #3
If u know its 5mph out whats the worry? U just do 25 on the gauge in a 30?
Fair point, doesn't quite answer what I was after though! Thats what we're doing right now, just wondering if its possible/how much it would cost to get it sorted :) Cheers for the reply though!
 

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Just out of curiosity, what are you gauging your speed against??? All speedos except calibrated speedos read around 3mph out against say a TomTom satnav, I work for the Old bill and we have our speedos calibrated by IRS, off the top of my head it costs approx £250-£300
 

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Discussion Starter #6
Just out of curiosity, what are you gauging your speed against??? All speedos except calibrated speedos read around 3mph out against say a TomTom satnav, I work for the Old bill and we have our speedos calibrated by IRS, off the top of my head it costs approx £250-£300
Brilliant this is the reply I was after, very helpful cheers mate! T: We're gauging it against a Garmin satnav which is up to date as well as a satnav app on the iPhone which both read the same, its about 4/5mph out. Not a big deal really, just a little niggle!

Cheers! :) A:
 

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Brilliant this is the reply I was after, very helpful cheers mate! T: We're gauging it against a Garmin satnav which is up to date as well as a satnav app on the iPhone which both read the same, its about 4/5mph out. Not a big deal really, just a little niggle!

Cheers! :) A:
Sat navs and apps dont allow for the topography of the terrain ie if you're going downhill or uphill it thinks you're on the flat.
Therefore they are not much more accurate than a speedo.
 

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Sat navs and apps dont allow for the topography of the terrain ie if you're going downhill or uphill it thinks you're on the flat.
Therefore they are not much more accurate than a speedo.
True, it was tested on the flat on the M4 though mate. :)
 

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Why not just get the correct size tyres fitted ........end of problem and the van will accelerate better and be more economical :*
 

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Sat navs and apps dont allow for the topography of the terrain ie if you're going downhill or uphill it thinks you're on the flat.
Therefore they are not much more accurate than a speedo.
Not quite accurate. What you're referring to is horizontal distance versus slope distance errors.

On flat level ground at constant speed with low HDOP and VDOP, your GPS will be accurate to within 10% of 1mph...that's far more accurate than any speedo, which can never allow for outside factors like tyre wear....
 
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