Hi has anyone had any differrences in speedo readings, my 2004 GU3 ZD30 at 100km/h actually reads around 95-96km/h by my gps, im running 265/75 16" dick cepek FC2, and as you go faster the gap widens a tad.
That discrepancy is standard in most cars, usually a 2~5% over reading.
If anything, it's an effective way to combat speeding - People think they're being cheeky and doing 5~10km over, but in actual fact they're going at the right speed.
Are 75% aspect standard for a GU3? if not it'll compound the discrepancy.
65% is standard for my GU1 so I think the speedo is calibrated for an average of that aspect combined with 260, 265 & 270 widths, so a slight variation is normal.