I recently had my car 4 wheel allingment set because of excesive wear on the inside of the two front tyres. The fronts are now illegal on the inside but the rears are fine.

The question I have is should I just replace the two front ones or should I replace all 4 and keep the rears as spares tyres incase of a puncture ?

Blackcircles are qouting 103.65 each fitted for Goodyear EAGLE F1 GSD3 215/45 R17 Z so we are talking either 200 or 400 quid so there is a serious cost difference.

The other worry that I have is that my SE has Sat Nav and I do not know if just changing the two front tyres will effect its accuracy ?

I only replace tyres in pairs.

Sat Nav accuracy - Nearly all of the time it should have a GPS signal so doesn't use the wheel information. There is the recalibrate option within the Sat Nav anyway.

Thanks Colin

I realise that there is the recalibrate option but have never used it - I was wondering if it just assumed a new tyre diameter based on four new tyres. Does it actualy recalibrate by asking you to drive a certain distance then ?

It seems to calibrate instantly when you are not moving - probably does something in the background.