Hi, I have just upgarded from 19" wheels on 255/50 tyres to 20" on 275/40 tyres and my question is that I have read about needing to tell the cars ecu about the change but is this really necessary? The rolling diameters are the same ( or almost given that differnent tyres manufacturers have slightley differing sizes anyway) Is there another reason for doing this such as suspension settings?

Thanks

I cannot definitively answer your question but what are you doing with your 19's?