Originally Posted By kin
Originally Posted By Will Wallis
I've noticed this too. I'm sure the speedo on my S1 over-reads by at least 10%. Has anybody else noticed this?
I think its normal for most cars to overread, but illegal to under read. When I was travelling at 80mph, the satnav reading was around 74.
Only the police vehicles have fully calibrated speedo.


This was the reason that many forces allowed the 10% plus 2 or 3mph margin. In other words, 35 in a 30mph and 80mph on the motorway.