[7summit7]

Thanks for you response. The original tyres were 45 profile and the speedo was about 3-4 km/hr out at 100 km/hr. ie to achieve 100 on the GPS I had to set the cruise at 103 this matched the speedo. The new tyres are 40 profile,so smaller in diameter. Now to achieve 100 on the GPS I need to set the cruise to 108.
It must be possible to calibrate the speedo as both 40 and 45 profile tyres are included on the tyre chart.
I was wondering if anyone has had this done.

Cheers
M