Thread: Adjusting RRS/D3 Speedo

Have you checked that with a GPS on a level long stretch?
I found by going to oversize tyres my speedo was more correct!

None that I am aware of. At work we can only adjust the rim size, not the profile size. There are aftermarket products that you can use to alter it, however I don't recommend it, as it is very tricky to do and will void your warranty for some parts of your car.

The best thing you can do is either use a gps speedo OR just remember that your speedo is a bit off and adjust your driving style ocordingly.

There may be other way but none that I am aware of. Happy driving!

I really think your speedo should be more accurate!

Garry, mine is almost exactly the same over read as yours, I've gone from the OEM 255/50/19 to the D3 size, 255/55/19. 100km/h is 103 according to my gps & the speed checker on the motorway over near Geelong

Cost me my 1st Aussie speeding ticket on my return from the UK at the weekend

I corrected my D4's speedo for my current tyres using Faultmate but there are several places in the D4 CCF where changes have to be made to keep the speedometer, odometer and cruise control speed syncronised if the change is going to be done properly. It includes converting the tyre's dynamic rolling radius in mm to 2 bytes of hex values as the most and least significant byte values for use by the odometer. I understand that the D4 CCF is quite different to the CCF in pre-MY10 D3/RRS.

The factory speedometer calibration setting of 3.5% + 2 kph (if the same as the D4) should make your speedo about right with the larger tyres although the odometer will show slightly less distance than actual.