The bicycle industry is full of niches. Just as a bike exists for virtually every type of riding--from road racing to mountain biking to commuting--there is a tire for just about every purpose. You won't necessarily find stock road tires on road bikes or standard mountain tires on mountain bikes. The application people use often depends more on how and where they ride their bike than what type of bike it is.
There are two primary types of tires. Road tires tend to be narrow with very little or no tread. Moutain tires are typically wider with a knobby tread. Great nuance exists, however, among bicycle tires. For example, as BikeTiresDirect.com explains, some cyclists use a class of tires called mountain bike road tires, designed for individuals who ride their mountain bikes on the street. These tires are narrower than standard mountain tires with less tread. Other riders require a wider, knobbier tire for use on a road bike that encounters rough terrain during commuting or cyclocross races, which take place on muddy and uneven courses.
As the late Sheldon Brown's website notes, knobby tread patterns on off-road tires prevent slippage by hooking into uneven spots on hard surfaces and locking into mud and other surfaces on soft terrain. Tires designed exclusively for road use have very little or no tread pattern at all. As Brown pointed out, tread is not necessary on pavement. Tire producers, however, use a small amount of tread on some road tires to put novice cyclists at ease. Even though many riders worry that the lack of tread will cause tires to slip in wet conditions, Brown says tires with tread slip just as much on a wet road.
Wider tires, according to Brown's website, require lower air pressure, while road tires need higher pressures. For your tire to perform optimally, Brown contends it should bulge out a bit when you sit on your bike. If it doesn't, your tire is likely over-inflated, and may burst due to excess pressure. Air pressure aside, wider tires generally provide a more comfortable ride since more rubber hits the road, literally, and absorbs bumps and vibration. Narrow tires are less forgiving, but faster.
Mountain bike tires are measured in inches. The diameter of most mountain bike tires is 26 inches. In addition to the diameter, you will also notice the width of your tire. For example, a 26 x 1.25-tire has a width of 1.25 inches. Mountain bike tires tend to range between 1.25 for road use up to 2.5 inches for hardcore mountain riding.
Road bike tires are measured in millimeters (mm). A standard size is 700 x 23 mm, indicating a diameter of 700 mm and a width of 23 mm. Road tires can be as narrow as 700 x 18 mm and as wide as 700 x 38 mm.
Intuition tells you to use the same size tire on both the front and rear of your bike. Sheldon Brown suggests otherwise. His website recommends, for example, using a wider front tire when your concern is handling and comfort. The wider front tire will encounter the road or trail's imperfections first. It will usually handle better and offer a plusher ride. When you ride off-road, a wide, knobby front tire is always a must. Without it, Brown claims you will most likely trash if a lack of tread prompts your bike to skid on a trail.
- Photo Credit bicycle wheel image by Wendi Evans from Fotolia.com bicycle wheel image by Horticulture from Fotolia.com