Superb Speedo and Odometer Calibration

[Yorkie6947]

Recently changed to a Superb from an Octavia and notice a difference in recorded mileage for the same journey. Octavia recorded mileage also agrees with my Sat Nav; Superb reads 168.4 miles for round trip, Octavia and Sat Nav both show 173.8 miles. Not sure about speedo - reckon that's out too! Superb has standard 225/40 R18 tyres, so calibration should be OK but might not be!. Thoughts?

[Superb170]

My daily commute was exactly 100kms on my last Superb with 225/45/17 and now with 225/40/40s on my L&K it comes up at 98km! Exact same journey and I've noticed it at other times too. I also notice speedo is out by a kilometre or two on the speed cameras versus my last one.

 

There is definitely an element of calibration involved - its as if the set up of the car is for 17s and when the 18s are added they don't take the extra tyre size into account.  If you put larger tyres on a car that was calibrated for a smaller tyre then you would expect the speedo to read slower than what you are actually covering.   I would have imagined however that when a factory fit diameter is included on a car that the calibration should allow for this.  Doesn't appear to be the case though.  I didn't notice any difference moving from 15s (yes they were tiny wheels!) to 16s on my Octavias or when I moved from 16s to 17s.  Its only on the L&K 18s!  Glad its not only me that notices that


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[Stinker]

Isn't there a +/- 5mph adjustment via maxi dot for winter tyres. Worth checking it's not set or maybe worth setting it?