not sure this is the right bit of the forum but hety ho

I'm trying to calibrate my speedo, Bike clocks with the speedo healer, I've got it reading about 3mph high at the moment at 60 according to the tomtom, I'm pretty happy with that as the tomtom shows both my road cars read about 4-5mph high at the same point.

How accurate is the tomtom? should I stick at that or tweak it a bit closer?
All tests done on 2 mile straight section of bypass

TomTom uses atomic clocks in space. Its accuracy is beyond reproach.

If you are at all worried (and IVA retest is £90) then have it read over a bit more, as the threshold on over reading is ridiculous (6mph + 10% or something). But, I guess you already have SVA/IVA from your testing methods ;-)

Matt

car and bike clocks all over read, the police have to get them calibrated to be accurate due to manufactures building in enough lee way to stop them being sued - and I guess to cater for bigger/smaller alloys within the range.

So what I'm saying is, the TOM TOM will be right, as long as your going a constant speed (they don't react as quick as a wheel driven speedo obviously)

cheers chaps, car is already on the road as you say so its just a requirement for keeping my licence nothing else

Just make sure the road you are using as the 'test' road is flat as I was told all GPS systems will give inaccurate readings if you are going up or down a hill.

Alan...