I am confused over the issue of winter tyres for my car. I have a 2007 Mercedes CLK fitted with AMG wheels. The tyres are 225/40 ZR 18 on the front and 255/35 ZR18 on the rear. Mercedes does not supply a wheel and winter tyre option in these 18" sizes. The vehicle owner's manual quotes winter wheels and tyres in 225/45 R 18 92H M+S XL size for all four wheels, but a new set of AMG alloys this size would be prohibitively expensive and any variation would not be acceptable to my Insurer. I do not feel that changing and rebalancing the tyres twice a year on one set of rims would be practical and if this was done then the winter tyres on the rear (255/35 X18) would not be the correct size as listed in the owner's manual. The use of snow chains is also not possible on the rear axle tyres according to the owner's manual. Do you have any experience of the Autosock Car Snow Socks, which are a reinforced textile cover that can be fitted to the driving wheels in particularly slippery conditions? The durability has to be questionable but maybe a supply of these would be cheaper than a fresh set of wheels with winter tyres? I have considered purchasing a cheap Ford Fiesta and fitting that with winter tyres, but the prospect of funding and maintaining this for the very few days of the year when the roads are truly impassable, is a daunting prospect. Please can you suggest a solution to this dilemma?