[Jamie Fisher]

Has anyone out there ever checked their speedo's accuracy over a measured kilometre (e.g. on the M4, M5, F3 etc.)with a stopwatch? I regularly test both vehicles that I drive and find that with both vehicles (a 1999 Mitsubishi Express Diesel van and a 1995 EF XR6) at 120km/h on the dial actually travelling at 112km/h and 114km/h respectively. There seems to be some algorithmic error because at 110km/h on the dial they measure 104km/h and 106km/h respectively. I had a 1995 Mitsubishi Express Diesel van and its results were identical to 1999 model. Is there some sort of error in all vehicles? Any ideas out there?

 

[QuarterPounder]

I haven't checked that carefully, but I know my odometer is about 5%-10% high, so I would expect my speedometer to read high by at least a similar margin.

Simon

 

[Timbo EF1XR8]

I have checked my car on the M4 at a range of speeds from 90-130+ and I have found my speedo to be 100% dead accurate. When I first got it, the speedo read 5% under (speedo 110, real speed 115). Real handy for the double points weekends, hey? I got a new gear put on the sender from the gearbox, and it is now perfect. My car has 16" rims and I think the gear they used was for a 15" setup.