Do all fords speedo's under read or is it just the cheaper fords (ie the ka ) that under read?

I'm always told by friends, speed warning signs and my sat nav that mine under-reads (KA). But how would you know for sure if it actually does??
This is something I've always been curious about.

They may read + or - 3mph as standard
But if you change wheel / tyre size then that can be exaggerated

I think my speedo under reads by about 10%. So it's normal then.....That's a relief. Thanks again Preee

The official Police guideline is allowance of 10% of the limit but that guideline can be rescinded if the person is driving other than in accordance of the highway code and road safety regulations.

Stoney , if i was driving at 120mph on the motorway would you still give me the 10% , or extra because i would be in a Ford

[quote name='Preee' timestamp='1329420318' post='167081']
Stoney , if i was driving at 120mph on the motorway would you still give me the 10% , or extra because i would be in a Ford
[/quote]

120 is not punished by a fixed penalty or endorsements, it would go straight to court with a recommendation for a instant disqual.
30% over the posted speed limit will result in this procedure i.e. 52 in a 40 zone, 39 in a 30.
Traffic / weather / visibility and many other things are also taken into consideration so the % allowance is only a guideline too.
What i don't see i can't act on.
What car sarge?

[quote name='Stoney871' timestamp='1329420984' post='167084']

What i don't see i can't act on.
What car sarge?
[/quote]

Gonna stick with the Ford then lol

[quote name='Preee' timestamp='1329421229' post='167087']
Gonna stick with the Ford then lol
[/quote]

Good idea i think.

Thanks for the info people

Most newer vehicles av driven are a few mph under the display and digital oners seem too be worse