As with the majority of components on a tandem the tires are usually designed with a single rider in mind. For tandem teams this fact must be evaluated first when selecting and using tires on both a road tandem or mountain tandem. To provide you with some tools to better evaluate the options available when buying tires we will define some of the designations found in tire marketing material.
Tires are manufactured with three major pieces combined into one unit; the bead, the casing, and the tread. These are discussed in further detail below.
Bead – The tire bead is the part of the tire that engages the lip of the rim; it can best be compared to the backbone. The bead “holds” the tire in place both laterally and vertically. Lower cost tires generally are manufactured with a wire bead. Wire bead tires can be quickly identified since they do not “fold”. Folding beads normally are manufactured with Kevlar or Nylon strands in place of the wire strands. This material is strong enough to engaged the lip of the rim while at the same time allowing the tire to be folded compactly when removed. The advantage of folding tires is found in weight saving over the wire bead counterpart and the easier mounting and dismounting associated with the more flexible bead.
Casing – If the bead is the backbone then the casing is the skeletal system. Casing is generally comprised of tightly woven fabric covered with light epoxy like rubber. The casing is easily visible from inside the tire or on skin-walls by the sidewall. Tire manufacturers often advertise the “Thread Count” of their casings. This is simply the count of the number of threads per square inch. A higher number generally yields a stronger and more supple tire but also results in a higher cost to purchase. In some examples you can purchase the same tread pattern with various thread casing – the simple difference being price versus comfort and dependability.
Some manufacturers also include Kevlar liners within the casing. This barrier helps form a puncture resistant liner between the tread and inner tube. There is a weight penalty but it is generally minor.
Road tandem teams should select high thread count cased tires. Mountain tandem teams can select lower thread count tires depending on tire width, trail usage, and other external factors (type and length of rides or inner tube selection for example). For most tandem teams the casing is what usually wears out forcing the purchase of new tires. The increased load factors on the sidewalls is incredibly stressful on the threads. Signs of wear on the casing include frayed threads, cuts in the sidewall, and excessive rubber material inside the tire.
Tread – The look of a tire is generally associated with the tread pattern. Tread is the skin of a tire and is the only part of your tandem that comes into contact with the road surface. On smooth, dry, and paved surfaces the ideal tread is smooth rubber. This creates the most contact for traction (think NASCAR tires). In the real world we ride our tandems on rough, dirty, and sometimes moist surfaces. This variability in terrain requires tire treads that are grooved to allow the imperfections to be cleared and the rubber to grip the hard surface. When selecting a tire keep in mind that a stylish aggressive look is not as important as a tire that can capably clear a path for rubber to meat asphalt. Talk with others in your area and find out what works best for them traction wise and start your search from there.
Comparing the three main aspects of tire design (bead, casing, and tread) against the associated prices of the tires will allow you to select the optimal tires for your tandem and budget.