My speedo in the 4/4 is reasonably accurate, at least until I've covered a few miles, then it could read anywhere from 10+mph over or under, inconsistently. The mileometer on the other hand under reads by some 15+%, so the car has travelled further than displayed. Only discovered the under read on a trip home from Aylesbury a couple of years ago, so whether it has always done it is anyone's guess.
The 90, courtesy of 7.50R16 tyres over reads speed slightly up to 40mph and then under reads a little from around 50mph, so displayed 60 is in reality 62mph The original 205R16s gave more than 10% over, so I resorted to a GPS based add on speedometer.
