Specifications
Touring bicycles are usually equipped with luggage racks front and rear, designed to hold panniers or other forms of luggage. To carry heavy loads, to be field-repairable and for reliability, touring bicycles typically have steel (CroMo) frames and forks. They may also have durable hubs, double-wall rims, and wheels with at least 36, and sometimes as many as 48, spokes, laced 3 or 4-cross. To accommodate long rides, touring bikes have comfortable handlebars and saddles. In fact there are many different bicycle handlebar arrangements available to touring cyclists, the choice of which is highly individual.
Touring bicycles may appear similar to road bicycles if they have drop handlebars. However, they greatly differ by typically having a much longer wheelbase and more stable steering geometry, with numerous attachments for luggage racks, fenders (mudguards), lights, high capacity water bottles, tools and spare parts. Chainstays must be long enough to accommodate panniers without them brushing the rider's heels, and the entire structure must be stiff enough to safely handle long, fast descents with the machine fully loaded.
Touring bicycles may also be fitted with 26-inch (ISO 559) wheels in preference over 700C (ISO 622). This is because ISO 559 wheels are used on mountain bicycles and are more durable and often easier to source in remote locations than 700C wheels. World bicycle tourers Tim and Cindie Travis are notable advocates of ISO 559 wheels for touring bicycles.
Instead of panniers, some riders prefer a bicycle trailer. Trailers are easy to use and allow touring with bikes on which it is impossible to attach racks. However, double wheeled trailers decrease maneuverability and are not particularly suited for touring in mountainous regions or on rugged terrain. On the other hand, single wheel trailers are extremely maneuverable, with the trailer wheel tracking very closely with the rear wheel. These can easily be ridden on single track trails (about 40 cm width), over some very technical terrain. Trailers have an advantage over panniers on single track trails because the bike itself carries no extra weight, except some on the rear axle attachment (the trailer itself can be loaded with up to 70 kg). This allows the rider to shift weight as if without load and clear logs or rocks (trailers will typically follow over anything the bottom bracket clears).
Touring bicycles traditionally use wide-ratio derailleur gears, often with a very low gear, in some countries called a "granny gear", for steep hills under load. Typically the gearing has a triple chainring similar to mountain bicycles, whereas most road bicycles have only two chainrings. Raleigh's 1985 catalogue lists touring bicycles that usually fitted with a 14-32 tooth 6-speed freewheel and 28/45/50-tooth chainrings, typically giving a gear range of 23 to 96 gear inches. A modern popular combination is to use an 11-34 tooth cassette with 22/32/44-tooth chainrings, typically giving a gear range from 18 to 104 gear inches. Internal-geared hubs with 5, 7, 8 or even 14 gear ratios have become an option in recent years because of their robustness and low maintenance. In particular, the Rohloff 14-speed hub with a gear range of over 500% has been used on at least two around-the world bicycle tours. Internal-geared hubs have a couple of advantages over traditional derailleur gears, in that they can use stronger chains as generally a single sprocket and chainring combination will be used. Secondly the spread of gears can be made more evenly, that is to say there are many duplicated and unusable gears in a derailleur geared setup.
Touring bicycles usually have linear-pull brakes or cantilever brakes, instead of the caliper brakes used on racing bicycles. Caliper brakes are less suitable because, to fit around mudguards (fenders) and wide tires, they become large and may flex when trying to stop a heavy bike. Some newer touring bikes use disc brakes, because of their greater stopping power in wet and muddy conditions and also to avoid outer rim wear. However, they are more complicated, so repairing them in remote locations can be difficult; they also weigh more than a cantilever brakes, increase the stresses on spokes, and require the front wheel to be dished, which reduces the durability of the wheels.
Thus, touring bikes trade speed for utility and ruggedness. This combination is popular with commuters and couriers as well.
Read more about this topic: Touring Bicycle