Hi, I live in the SF Bay Area where icy/snowy conditions are very rare. I also have the 21" rims with summer tires on my P85D. For the occasional encounter with snow (Tahoe, Yosemite, or just Santa Cruz mountains or Lick Observatory), is it reasonable to rely on a set of auto socks (2 pairs to cover all wheels) to bail me out of a snow emergency? Anybody got experience with those on 21"? Does the tire underneath (and its tread pattern/compound) make any difference? (I ask because the socks cover the tire and provide an alternative grip, so maybe the fact that my original tires are summer tires is not a negative). Thanks for any info!