Noone likes a liar...

[jetpilot]

The only other way you can check is by doing a speed check over a measured mile, run at 70, 80 whatever, time the run on a stopwatch and then do the maths, time taken etc etc.
But there is no way i would belive a GPS to be innacurate unless you have a very very poor signal which keeps dropping out.

[Spotlamp]

The Apexi PFC has a speed calculation jobber in it.  At 30mph both speedo and PFC read 30mph, but at a speedo indicated 70mph the PFC reads around 66mph.

I\'ve not been faster than that ociffer so can only speculate that the problem seems to get to certain degree of inaccuracy (-5 or -6pmh in may case) and remain there above 70mph.

Would love to know which one\'s actually correct, am inclined to believe the PFC as I guess it works off rpm and some stuff in the gearbox...

H

[the lemster]

very interestin thread this....

and it got me to thinking...

if your speedo is reading 70 and you are only doing 66.... does this mean that  your milometer is out as well...

are we putting 70 miles on our clocks when we have only travelled 66...  those 4 or 5 miles will soon start to add up...

I know it is only 5 miles home from work, but the other day I put on 25 miles... just going home.... somethings askew here... or was it just a nice day for some b road driving... hmmm

[nikp]

Speedo\'s are meant to over read. They are designed to. And the faster you go, the more they\'ll over-read There are 2 reasons for this:

1. It\'s actually very expensive for a manufacturer to produce a 100% accurate speedo.
2. Safety!

I speedo suspected my speedo to be reading kph a while back, so got a mate with GPS to ride along with me and confirm it - which showed it was reading kph. It\'s back to reading mph now!