false speedo reading

[grizzlya58]

hi.can anyone tell me why my speedo reading is out.i was checking the speed on the satnav and my speedo seems to be 5mph out.when doing 50mph. actually only doing 45mph. my wheel and tyre size are 215/65 r15 96H front and rear, I was wondering why people were pissed of with me when doing 30. any advice would be good thanks. colin.

[notlob]

No doubt others will be along in a while about specifics to the Bongo but I find that most car speedos read over what your actual speed is. I recon 10% over is not too unusual?

Dave

[g8dhe]

It could be as simple as the needle just having been put back in the wrong position when the Km/Hr to MpH change was made, in which case it will show a constant offset. If however the % difference varies with speed then more likely to be a factor associated with the tyres and there sizes. See here for how to correct http://www.igmaynard.co.uk/bongo/forum/ ... 73#p405273

[Dodgey]

I'm on stock tyres and my speed always over-reads by 6mph - checked against GPS.

Saves me fuel and reduces my speeding fines so I live with it

[pc13cb92]

Hi,
when I changed my speedo face I took a lot of time and patience getting the needle in the correct position, using my sat nav, and two local speedo indication signs. I reads spot on at 30mph but at an indicated 70mph I'm really only doing 64mph. At least it's in the right direction. The difference must be in the mazda design. I'm on 215/65 all round.


1996 2.5td 2wd aft

[the1andonly]

I agree with pc13cb02 ( how do you remember username let alone password)
i spent a lot of time recalibrating kph to mph using 2 vehicles and an audio comunication device and time and distance measurements, then eventualy checked with twatnav. 30mph spot on nearer 65+-1 @70.
remember on a motorway there are 1/10 mile markers (little sticks on hard shoulder) 60mph=1mile per min ie 10 sticks (they are numbered) a quick sanity check with just a stopwatch (phone)