45x17 on my Gitane TdF conversion, 42x16 on my purpose-built Mercian, both of which are roughly 70-in gears on 28 mm Panaracer Paselas. I mostly ride over rolling terrain in an area bounded by man-made lakes. I keep 45x19 or 42x18 (63-ish-inch) on the other side of the hubs, but it's been a while since I did any serious dirt road cycling.