• Registered users are encouraged to enable MFA/2FA to add an aditional layer of security to their account. More information can be found here: https://www.ncsc.gov.uk/collection/top-tips-for-staying-secure-online/activate-2-step-verification-on-your-email

FK8 Accuracy of speedometer

Messages
79
Just been on our first reasonably long run and my wife has been getting flashed out of the way a few times whilst sitting at 70 with the ACC set at 70. Loaded up my Android GPS app and it reports the car doing just under 66.

Set the ACC to 73 and the app now says 69.

Anyone else noticed this.
 
Pretty much every car over-reads to a small percentage, if nothing else because it's preferable to under-reading.
 
This is normal. Mine is pretty accurate up to around 30mph, then the higher the speedometer reads the less accurate it is.
I believe these were regulations set so you could not be prosecuted for speeding when it is not the drivers fault e.g. Your speedo reads 70mph but you are doing 75mph.


Sent from my iPhone using Tapatalk
 
Extract from www.speed-trap.co.uk:

Vehicle construction and use regulations require a vehicle speedometer accuracy to be in the range of -0->+10%. The implications are that it must never under-read - for obvious reasons - but may over-read. As the cost of manufacturing a speedometer with -0% error would be very costly they all over-read by a few percent without exception. Even if speed is measured correctly the display may not be accurate, so a speedometer error is allowed

I see a 7% inaccuracy from 30-70, but unsure if it's actually due to the above or if it's a preset safety margin (if the latter then does the odometer take that into account?). Going to a 35 profile tyre will correct this (and are more easy to obtain)
 
Last edited by a moderator:
Cheers for the replies guys. We will just set the ACC at 73 rather than 70 and that's it fixed.

Thanks!
 
Back
Top