Originally Posted by Myosmith

I also notice that "slipping crank" feeling when riding in some winter conditions. I came to the conclusion that it was actually the rear tire (Schwalbe Winter 700x40) breaking traction when I would start mashing to maintain momentum in deeper snow. It seems to happen more when I stand than when I sit and spin in a lower gear. I've felt something similar when I rode on damp sandy gravel and would stand during climbs.