Choosing a dirt-capable tire isn’t as simple as throwing on the biggest knobby that you can find. You can certainly go that route if you ride off-road 100% of the time, but if you want to cover pavement, dirt, and gravel on a single set of tires, you’ll need to make some compromises.
The first criteria to consider when selecting a tire for on- and off-road use is size. And in this case, bigger is almost always better. You don’t necessarily need a full-sized MTB tire, but you’ll definitely want something larger than a 23 mm slick. Riding off-pavement is generally more fun (and safer) with lower air pressure, and skinny tires just don’t have the air volume necessary to run low PSI and still protect the tube and rim from rocks, etc. The larger the tire’s cross section, the more cushion between you and terra firma. Whatever size tire you choose, make sure there’s enough clearance at the brakes, frame, and especially the fork, so that the wheel can’t become locked by any type of object stuck to the tire.
Tire selection criteria isn’t limited to just size or volume. Different types of tread perform better on certain types of terrain. If the trails and roads you’ll be exploring are composed of very hard, sun-baked dirt, you can get by with a less aggressive tread pattern. In these types of conditions, a lightly treaded tire such as the Panaracer Pasela or Continental Contact will offer enough off-road traction, while still being efficient enough for extended paved riding. If, however, you’ll be riding on soft, loamy soil (or loose gravel), you’ll want something with a more aggressive tread. Thankfully, with cyclo-cross’s increased popularity, there’s no shortage of lightweight, road-friendly knobbies
Whichever type of tire you choose, take some time to experiment with different air pressures. Often times a change of only 3-4 PSI is enough to turn a so-so tire into a great one. The key to off-road comfort and control is balancing traction, efficiency, and rim/tube protection. If you’re feeling every single pebble, you’ve definitely got too much air, and if you’re constantly bottoming out (and flatting), you need to add some air. Once you find the sweet spot, you should be able to comfortably ride different types of terrain without making any major changes (but it’s not a bad idea to add some air for long paved sections).
Remember that there is no one ideal tire for all conditions and terrain. Ultimately you have to make a compromise, whether it’s on-road efficiency, weight, or even cost. Pick the attributes that are most important to you, and look for tires that can fulfill those needs. Riding and exploring on any tire is always more fun than searching for the mythical “perfect” tire.