Has anyone noticed that their Speedometer reads high? My Speedo was reading 10.5% high and the dealer has now got it to read 8.5% high. Other S60s they tested was reading 9% high. Volvo say that this is in spec. Is this a general problem or only on UK cars?
Do you have the appropriate size wheels and tires on your car? I know that having wheels and tires other than standard sizes can effect the speedometer reading to different degrees. 15, 16, 17, and 18 inch wheels can give a different margin of error.
On my 2001 V70 (everything should be the same as on your car) the speedo is well withing 1mph error over the entire range (well, at leaset over the range I've tested from 0 - 131mph)
I agree with Drew that wheel/tire sizes will be the most likely culprit. The speedo is probably calibrated to the stock set of wheels, and if you ordered an upgrade, or changed them yourself, the rolling diameter will most definitely be different. Tire sizes are just rough estimates of the actual dimensions, unfortunately.