One of the surprising things I found about my Pugsley is the incredible difference that even 1-2psi of pressure makes in the snow. I run a Nate on the rear and a Larry on the front. On marginal conditions, like churned-up trail with 4-5 inches of snow, 10psi is unusable, while 8psi works just fine. There have been a couple of times when I went down to 4psi.
A fat bike will certainly not let you go through everything, but here in upstate NY with 100+ inches of snow a year it makes year-round riding possible. I think there was only one week where I couldn't put at least 20 miles on the Pugs.
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Knows the weight of my bike to the nearest 10 pounds.