The difference is information vs ramblings/rants
I actually run the stock size for a few reasons:
1) I knew the dry handling would be squirmy/squirrelly so I figured the 245 wide tires would help the dry performance.
2) Although the general theory is narrower is better for winter performance, the gains are in specific areas. One of the key gains is that the narrower tire cuts through snow more easily and as such has lower rolling resistance. Folks also like to thick of the narrower tires as cutting through the snow to reach the firmer ground but that advantage for a narrower tire only happens under a very narrow range of conditions with non-studded tires, i.e. no significant advantage there. And the siping plays more of a role in ice traction than the width of the tire between say a 225 vs 245 width. On deeper snow, a wider tire is actually going to be better (especially for a low slung vehicle).
3) I couldn't find 225 sizes that worked too well for 18" wheels. (they only have 225/40/18 which makes for a very short sidewall and quite a bit smaller than stock rolling circumference).
1 & 2 were the main reasons I didn't run narrower sizes.
On 17x8.5 wheels, I would personally run the stock 245/45/17 for the reasons O stated, although in 17", they DO offer 225/50/17 which is usable for folks preferring the 'narrower for winter' approach (only 0.7% difference in rolling circumference). Personally, in the amateur rallying that I used to do, I found it only really effective with narrow studded tires. The narrow tires would cut through the snow and the studs would dig in the dirt or ice layer.
With non-studded tires, the tires cutting down to the ice layer didn't help much and you would only hit the dirt layer with narrower tires if it was light snow (not packed from other vehicles driving over it) and there was less than ~1.5" of it. The only slight difference it made was in drifting, where the narrower tires would dig in and be a little more resistant to sliding sideways as they would build a berm/bank against the side of the wheel. Everything's a compromise so I chose to sacrifice the (not-as-common-IMO) region where narrower non-studded tires would be a benefit in exchange for better dry performance.
Max







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