Speedo accuracy??

[Ozzie]

I've just survived a trip to Milton Keynes Ikea, but to top it off I got stopped by the police after I overtook a police car whilst I was doing 60 mph in a 60 zone. However Mr PC says I was doing 65, and his speedo is calibrated, I said well my speedo says 60 and the sat nav says 58 (as observed by Mrs O.). He says well hes a policeman so basically he is right, I said I'm a driving instructor and am I going to risk my livlihood?
He then suggests I get the speedo checked, he reminds me to obey the speed limit and walks back to his car. So no real problems, I just wondered if anyone else has speedo accuracy concerns or if anyone has had their speedo recalibrated??

[culzean]

Sounds like he was trying it on,  I have noticed police often travel slower than the speed limit (they mostly do about 60 on motorway) to see if someone has the balls to overtake them,  and also maybe so that they get to see more cars number plates with their ANPR cameras as cars go past them.

My Speedo normally reads a couple of MPH more than my satnav and if I go past those light up speed limit reminder signs at correct indicated speed they don't activate so I assume speedo is OK.

[Eddie Honda]

Jumped up plod.

Any vehicle speedo will rely on the size of the tyres. These get bigger when their hot. They'll be bigger if they are inflated more. They'll be bigger when they're new. They'll be a different size depend on wheel and tyre combo. Manufacturers sizes of a given designation will be different.

ACPO guidelines (and they are guidelines, are generally 10% + 2mph. I make that 68 for a 60.

Did you get a ticket - no.

He was obviously p'd off that a Jazz overtook him!

I've no speedo accuracy concerns btw.

[John Ratsey]

My Hybrid reads about 1 mph high at 60 when compared to the sat nav. Most of my pre-Jazz vehicles have been around 10% high on the mph, possibly to help keep people within the speed limit or more likely to make people think that their car will go faster than it really wants to.

On this occasion I would support you and not Mr Plod. Perhaps his car is one of those that reads 10% fast and, unless someone put a new set of marking on the dial / alter the computer firmware I don't know how any attempt at calibration would result in a change to the displayed speed.

John

[guest4078]

My speedo reads pretty accurate too, similar to John.
If he was an 'officer' from Northants, I am not surprised he tried it on, they are £$"%^&*'s.
They tried to give me a speeding ticket in Northampton from a mobile gatso when I was 2 counties away!
Chief constable probably wants a new Range Rover Overfinch for christmas.

[monkeydave]

my jazz speedo is correct and the same as my tom tom on my 15" steel wheels and 175/65 15 tyres.

on my civic it showed 4 mph faster because of the upgraded wheels and 50 profile tyres not 55 profile.


they wont give you a ticket as they use the 10% plus 2mph so 68 and above would be a ticket