Winter tyres on a C-Class

I've just bought the above car from an independent dealer which came with one years MOT.
Due to the recent snow in the North East of England I'm thinking of fitting winter tyres, however the current tyres are two different sizes, the rear are 245/40R17Y whereas the front are 225/35/R17Y.
I appreciate that the tyre width is usually greater on the rear axle but is it normal to have different profile depths?

Asked on 13 December 2015 by Derreck Pinkney

Answered by Honest John
That's the wrong way round. And incorrect. The rears should be 245/40 and the fronts 225/45. You can fit 225/45 R17 91W winter tyres or Cross Climates all round.
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