Usualy under the speed limit + 10% + 2mph. Someone once gave me that formula and it seems to have worked up to now:-) Funny thing is now I have got a SatNav as well I can often get 2 readings - With the SatNav always showing lower than the speedo.

Here's an intersting thing. A couple of years back a TV documentary sampled about 100 cars and every one had speedometer errors. Funny thing was each one showd less than they were doing at the bottom end and more than they were doing at the top end. Ie if it showed 20 they were doing 25 - If it showed 80 they were doing 75!

I would seriously ask you all to remember a fact that they have shown on UK roadside posters for years.

If you hit a pedestrian at 30mph there is an 80% chance of survival. At 40mph there is a 90% chance killing a pedestrian

Be careful out there!

Cheers

Dave