Speedo accuracy

[asthpsw]

I have a 2001 Toledo so is getting a bit aged now. I have recently bought a Garmin SatNav.

I note there is a big difference in the Speed on my Speedo as against that on the SatNav (e.g on Speedo 77-78mph and 69-70mph on Sat Nav.

Has anyone experience of this and which is more accurate ?

I do re call that I once heard car manufatures get the speedo to read faster than real speed to prevent driver unknowingly exceed speed limits especially as vehicle ages ?

Paul

 

[Phillips1795]

Hi Paul,

My TomTom reads about 5 mph slower than my speedo.

I'm under the same impression as you with regards to them being like this.

I have noticed it is pretty much the same in all the cars I've been in with a sat nav.


Sent from my iPhone using Tapatalk

 

[Dox1966]

What size tyres are fitted to your car? Speedos have to over read by law to ensure you cant unknowingly speed

 

[Slimy]

A speedo can read up to 10% too high, so most manufacturers err on the side of caution to make sure it's in range.

My speedo reads 75 when my sat navs (all of them) read 69. So the majority vote suggests my speedo is wrong.

 

[Muttley]

Construction and use regulations say that the speedometer *must* *not* read lower than your actual speed, but can read up to 10% high. Therefore *all* car speedometers read high, it saves the manufacturer from expensive recalls and legal penalties.

If they can make a speedo that is +/- 2% inaccurate, they will set the speedo to read +5% over actual road speed, to ensure they are always legal.

 

[Sjx]

75 on the dial is 70 on GPS, OBD & Climatronic in mine.

Standard wheels & tyre sizes as well.