Fast? Is it a race? My bikepacking routes take me on dirt roads, bikepaths, single track and the occasional " off road/trail/ bushwacking. Only use pave to connect them. My Krampus with 3" tires is wicked fast. Never had another Krampus pass me. Is your goal to be head down on aerobars all day? Or sitting up taking in the sights and sounds that nature provides. The fast is up to the rider, really.