The best touring bike may be the one that's already in your garage. Cyclocross bikes follow the design of a traditional road racing bike, but stronger materials designed for off-roading and a higher tire clearance make them uniquely suited for conversion into a touring bike. As long as you're willing to keep your touring load relatively light, there's no need to purchase a second bike for multi-day bicycle trips. You'll need to add a few things to your cyclocross bike for touring, including racks and bags. Once you've dialed in your setup, you'll be ready for a serious touring adventure.
Replace your cyclocross tires with smooth road tires. Since almost all bicycle tours happen on roads, these smooth tires will decrease your rolling resistance and make pedaling easier. You'll want a wide tire with a durable flat-resistant rubber; 32mm is ideal, but you'll need to make sure there's enough clearance for your rim brakes, frame and fork. Run the widest tire your bike will accommodate for the most comfort and flat protection.
Outfit your frame with racks for carrying bags. If you're using a steel frame cyclocross bike, you may already have rack mounts that can be used to attach a traditional rack. For other cyclocross bikes without rack mounts, a rack that clamps to the seatpost can usually hold 10 to 20 pounds of gear without a problem. Tighten the rack securely using a hex wrench, and double-check all bolts daily to make sure nothing loosens up as you ride.
Attach a handlebar bag by clamping the mount to your handlebars. A handlebar bag allows quick access to commonly used items like lip balm, a cell phone and snacks. Most handlebar bags use a plastic mounting bracket that will attach on either side of the bike's stem, which should be compatible with the drop bars.
Fit your bike with enough bags to carry your gear. Your rear rack should carry the bulk of your touring load, which will often include a tent, sleeping bag, camp stove and food. Additional bags mounted underneath your seat, on your front rack and in the triangle of your frame can store things like extra clothing and spare tubes.
Add reflectors and a bicycle computer. It's important to be seen when you're on the road for several hours a day, so use reflective tape and clamp-on reflectors to increase your visibility in low light. A bicycle computer is also an important touring-specific gadget, as knowing your traveled distance will make navigating with a map much easier. If you don't have a bicycle computer, you can still tour, but following directions becomes a bit more difficult.
Using a bolt-specific adhesive on all of your rack attachment points will prevent road vibration from loosening bolts over time, which is especially important for seatpost racks.
Don't overload a cyclocross bike with too much equipment. If your touring load exceeds 40 pounds, you will likely need a touring bike to accommodate it. For tips on decreasing your load, your local backpacking outfitter should have the expertise and equipment for traveling light.