I have a 1.6 16v twinport 05 Astra which needed new tyres so i decided to get some new wheels.
The wheels it came with were 205/55/16.
My new wheels are 205/40/17
I've also lowered it by 45mm and i like the look of it so don't really want to change again.
My problem is that the speedo now runs 5.7% too fast.
This means when i think i'm doing 60mph i'm actually only doing 56.6mph
Is there anyway that vauxhall can re-calibrate my speedo to give the correct reading?