: shows 105 kph when gps shows 100 kph. Tyre size was standard ( 195/65R14 Michelin ). Has any1 here noticed this difference ?
My gps reading is correct ; [i] my 2 cars ( Proton & Honda ) use taller tyres than original, & this receiver correctly reports the proportionately higher readings than speedos'. [ii] from gear ratios & axle heights & zero toe-in, I can calculate speed @ different engine rpm.
you'd be hard pressed to find any car these days that doesn't read fast In Australia the old design rules stated a speedo must be accurate to within 10% +/- but around 2002 they changed it to be just 10% -/0
all my cars read around 5kph fast, changing my Landcruiser tyres from 31 inch to 33 inch made the speedo read true
This of course led the way for the Govt to make laws that make it possible to be booked for speeding by 1kph over the speed limit and arguing speedo error won't hold up
Our Trucks must be speed limited to 100KPH, but this speed limiting is tested on Dynos not the off the vehicle's speedo, therefore you have a truck driving along at 100kph and passing cars doing just 90-95kph. Then these car drivers would call the Police and complain about all the speeding trucks not realising that their speedo was at fault not the truck drivers
Kev
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