I couldn't imagine driving with my 315 rear setup as they would float over the snow all the time. Even if I ran it at 10psi, it wouldn't be as good as a narrow tire right? So we all agree narrow is better in this case. In mud for example, we want the exact opposite cause we want to float rather than sink. I can see a certain logic to inflate so that the tire stays narrower. As an Enduro rider , we deflate because we want the tire to FLEX over uneven structure so that it can grab whatever it can and create GRIP. There is not much to grip on cold asphalt so I don't really see the need to deflate lower than the recomended psi.

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His : 2005 X5 4.8is (SOLD)
Hers: 2007 X5 3.0si (SOLD)
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Retired:
1999 518
2000 323i
2002 M3 (beautiful car)
2003 330Ci