I really loved the speed of my Challenge Race tires, but I flatted almost weekly with them. Not worth the effort! Years ago, I used to ride Schwalbe Blizzards. They were cheap, but never flatted. I put them on my commuter at the beginning of winter after the Challenge tires had flatted so much, but they were an exhausting, slow ride. I ended up putting Micheline Pros on both my bikes. They're durable and fast, and come in nice colors.