Bicycle tires and tubes come in a wide variety of sizes, treads, thicknesses, and styles to accommodate different styles of bicycle riding and different trail and road conditions. Most bicycles require both bicycle tires and tubes to function properly, while others need only a tire that runs tubeless. Another type of tire is also the tube itself; this tire is known as a tubular tire and it must be glued to a specially designed rim to work properly. Narrowing down one's search for tires and tubes starts by determining what type of bike the tires and tubes will go on, and what type of riding will be done.
The two most common sizes of bicycle tires and tubes are 26 inches for mountain bikes and many cruisers, and 700c for road bikes, cruisers, cyclocross bikes, and many others. 26 inch tires and tubes are smaller in diameter than 700c bicycle tires and tubes, and they are usually wider to accommodate the impacts a mountain bike is likely to endure. The tubes may be thicker than 700c tubes, but this is not always necessarily the case. The tread on 26 inch tires may be knobby for off-road use or smooth for on-road use, and some 26 inch tires are semi-slick, which means they are smooth down the center of the tire and knobby on the sides for better cornering.
Tubes generally come in two styles, dictated by the type of valve: Presta and Schrader. Schrader valves are the type of valves used on car tires, and they are common on some mountain bikes, cruisers, and other models. Presta valves are much skinnier to cut down on the size of the hole that needs to be drilled into the bike rim; the smaller the hole, the stronger the rim will be. Presta valves are common on higher-end mountain bikes, road bikes, cyclocross bikes, and a variety of other bicycles.
Bicycle tires and tubes are almost always made from some sort of rubber, though other materials are available. The tires may have a steel or a Kevlar bead; the bead is the part of the tire that comes in contact with the rim to keep the tire in place. Kevlar beads are much lighter, and they are flexible to make the tire foldable for storage. Steel beads are heavier and more rigid, and they are also less expensive.