My car is a Vauxhall Meriva 1.7 CDTi XP, which means that it is factory fitted with 205/45 R17 tyres. These tyres have been fine in the good weather but have offered very little grip in snow and icy conditions. Therefore I am looking to change these before our next winter arrives. Would it be possible to fit 15-inch rims with 185/60 tyres? The owner's manual lists 185/60 R15 tyres for this engine type, as well as the 205/45 R17 tyres that are currently fitted. Who should I check such an alteration with? The local Vauxhall dealership have proved hopeless.