Took the trouble to try to calibrate the speedo in my S60 today (2.0 SE auto with 17" wheels and correct 45 profile tyres) - no particular reason, just out of interest. AIUI, UK legislation requires +0 -5% accuracy, but I'm overreading by about 8.5% at 60, 70 and 80 (didn't check any others). I used the 100m markers on the motorway, and set the cruise. The timings were pretty repeatable. I suppose the markers could be inaccurate, but it doesn't seem very likely. Interestingly I measured 16 posts to an indicated mile, which would seem to indicate that the odometer is pretty accurate (and confirms that they are at 100m, not 100yd intervals). Has anyone else tried this? It's disappointing that the error is this large and (strictly speaking) illegal. Tim