Incorrect speed reading on Tacho

ASK THE EXPERTS SAFETY, LAW AND WORKING TIME DIRECTIVE FORUM (INTE
1

Hope someone can give me an answer (or at least some advice) on this…

A few weeks ago, my tacho (analogue) went wrong - took it in to dealer and it had to be replaced (reconditioned unit).
Calibration carried out.
Within the last 4 weeks, I have been caught speeding twice!! Although I am no angel, I am also not reckless so had a close look at charts at specified speeding times and there seemed to be a discrepancy. So today, I got one of our other drivers and a driver from another company who share the yard (both of whom still have analogue tachos) and we went for a drive to compare speed readings.
The result is that my speedo/tacho is reading between 4mph and 5mph BELOW actual speed. (This is compared to the other 2 trucks and 3 Satnavs).
The trace is recording what the speedo says, but the speed is definitely reading low.
Now the big question - do I have an argument regarding the speeding charge (both were less than 5mph over the limit) and if so, do I fight it myself or do I get someone else involved?
Any help would be greatly appreciated.

2

I would take the tacho for repair and get them to write an engineers report for you.providing you have not been speeding over the discrepancy and the judge is in a good mood you just might get away with it :wink:

3

You need to see the certificate that they used when they calibrated the unit. Are the tyres the correct diameter for the calculation. Has someone changed the settings on the rolling road.

Even if the analogue chart was reading true, a magistrate will not accept evidence from it, you could have driven the same route the following day at the same time.