Personally we run around 9s or 10s. I ride upstate new york and it gets icy up there. Studs and sharp carbide are an utter MUST! Ppl say oh well this is enough or that is or I will be fine without studs. I had a friend who had sharp carbides and no studs. He came around a corner his end washed out and just bucked him off. He landed on a rock and busted a couple ribs and punctured a lung. We personally prefer to lean on the side of safety when it comes to machines capable of doing 100MPH on ice.