speedo

[Colin ingoe]

i have a 2.4 toyota estima auto, 2006. when i am driving my speedo reads 70 mph but my sat nav reads approx 63 mph is there any way of calibrating the car to the correct speed. T.I.A

[flash22]

Has it got aftermarket wheels ? Correct size tires ? has it had a speedo conversion ? Has it had the gauge face changed ? Or does it still have a kph one ?

[FROSTYBALLS]

In the UK, legislation requires speedometers to be optimistic within certain limits. A speedometer must never show less than the actual speed (ie. under read), and must never show more than 110%of the actual speed. Additionally for all actual speeds between 25 and 70mph, the indicated speed must not exceed 110% plus 6.25mph. For example if a vehicle is travelling at an actual speed of 50mph, the speedometer must not show less than 50mph and not more than 61.25mph.

So if your vehicle is travelling at an actual speed of 63mph and your speedometer reads 70mph, it is within the legal requirements.

The speed produced by GPS is an average over a given number of points and hills may affect accuracy, so, although more accurate than the speedometer, GPS doesn't quite show the actual speed.

Changes in wheels and tyres can affect speedometer accuracy, and there are websites available that can calculate effects on speedometer accuracy if one were to change the tyre size. Eg. http://www.autopartuk.com/tyre-calculator/

[Colin ingoe]

1 hour ago, flash22 said:

Has it got aftermarket wheels ? Correct size tires ? has it had a speedo conversion ? Has it had the gauge face changed ? Or does it still have a kph one ?

wheels and tyres are all correct it has an mph speedo in it, thats all i know. i bought the car from an import dealer and he said there is nothing i can do 

 

[Ruslan]

My speedo was showing similar figures. I removed canbus speedo converter unit and replaced with new dials in miles. Even after that speedo showing greater speed than gps, but it’s more realistic number now.