I've recently switched from 18s with wider at the back to 17s same size - 245/45. I fitted Pirelli 210s. In general driving they don't feel much different to the P-Zeros I have on my 18s. Most winter driving in this country will be in the wet with occasional snow, so I preferred not to reduce the width. 245/45 R17s were in my manual.
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So you followed the manual... I might do the same...