Apologies if the snow tyre discussion has already been done today 
I'd heard Innerleithen was under a fair bit of snow which had iced over this morning so chucked on the Schwalbe Snow Studs, these ones:
http://www.chainreactioncycles.com/Models.aspx?ModelID=24564
Turned up at Glentress, no snow at all, ice looked ok so went to Inners.
Absolutely hated the tyres. Don't get me wrong, show them a fully snowy or icy part of the trail and they were amazing but the marginal parts where there were rocks sticking out the metal studs were sliding off the rock. After it happened the first few times I just couldn't get any confidence when they were going to cut through to the rock and slide. Not even a gentle slide, felt like a normal tyre when it hits ice.
Will definitely try them again but only if the conditions have gone to full on hard packed ice, it was pretty astonishing how much grip they had on the few bits like that I found. Also need to play about with the pressure a bit I think...
