Bicycle tire

A bicycle tire is a tire that fits on the wheel of a bicycle or similar vehicle. They may also be used on wheelchairs and handcycles, especially for racing. Bicycle tires provide an important source of suspension, generate the lateral forces necessary for balancing and turning, and generate the longitudinal forces necessary for propulsion and braking. Although the use of a pneumatic tire greatly reduces rolling resistance compared to the use of a rigid wheel or solid tire, the tires are still typically the second largest source, after air drag, of power consumption on a level road. The modern detachable pneumatic bicycle tire contributed to the popularity and eventual dominance of the safety bicycle.
Bicycle tires are also used on unicycles, tricycles, quadracycles, tandem bicycles, bicycle trailers, and trailer bikes.
History.
The first bicycle "tires" were iron bands on the wooden wheels of velocipedes. These were followed by solid rubber tires on penny-farthings. The first patent for "rubberized wheels" was granted to Clément Ader in 1868. In an attempt to soften the ride, rubber tires with a hollow core were also tried.
The first practical pneumatic tire was made by John Boyd Dunlop in 1887 for his son's bicycle, in an effort to prevent the headaches his son had while riding on rough roads. (Dunlop's patent was later declared invalid because of prior art by fellow Scot Robert William Thomson.) Dunlop is credited with "realizing rubber could withstand the wear and tear of being a tire while retaining its resilience". This led to the founding of Dunlop Pneumatic Tyre Co. Ltd in 1889. By 1890, it began adding a tough canvas layer to the rubber to reduce punctures. Racers quickly adopted the pneumatic tire for the increase in speed it enabled.
Finally, the detachable tire was introduced in 1891 by Édouard Michelin. It was held on the rim with clamps, instead of glue, and could be removed to replace or patch the separate inner tube.
Attaching to the rim.
Three main techniques for attaching a bicycle tire to a rim have been developed: clincher, wired and tubular. Clinchers originally did not have wire in the beads and the shape of the bead interlocked with a flange on the rim, relying on air pressure to hold the tire bead in place. However, this type of tire is no longer in general use and the term "clincher" has transferred to the modern wired-on tire. For the remainder of this article, the modern use of the word "clincher" will be assumed.
In an attempt to provide the best attributes of both wired and tubular methods, tubular clinchers have also been offered.
Clincher.
Most bicycle tires are clincher for use with "clincher" rims. These tires have a steel wire or Kevlar fiber bead that interlocks with flanges in the rim. A separate airtight inner tube enclosed by the rim supports the tire carcass and maintains the bead lock. An advantage of this system is that the inner tube can be easily accessed in the case of a leak to be patched or replaced.
The ISO 5775-2 standard defines designations for bicycle rims. It distinguishes between
Traditional wired-on rims were straight-sided. Various "hook" (also called "crochet") designs re-emerged in the 1970s to hold the bead of the tire in place, resulting in the modern clincher design. This allows higher () air pressures than older wired-on tires. In these designs, it is the interlocking of the bead with the rim, not the tight fit or resistance to stretching of the bead, that keeps the tire on the rim and contains the air pressure.
Some clincher tires can be used without tubes in a system which is referred to as tubeless. Typical tubeless tires have airtight sidewalls and beads which are designed to maximize the seal against the rim.
Tubular or sew-up.
Some tires are torus-shaped and attached to tubular rims with adhesive. The rim provides a shallow circular outer cross-section in which the tire lies instead of flanges on which tire beads seat.
Providing suspension.
Adequate stiffness is necessary to support the rider, while softness is desirable for cushioning. Most bicycle tires are pneumatic—the stiffness is provided by pressurized air. Airless tires use some kind of elastomer instead.
Pneumatic tires.
In a pneumatic tire, pressurized air is held inside either with a separate, relatively impermeable inner tube, or by the tire and rim, in a tubeless system. Pneumatic tires are superior in providing effective cushioning while keeping rolling resistance very low.
Tubed.
A tubed tire has a separate inner tube, made of butyl rubber or latex, that provides a relatively airtight barrier inside the tire. A vast majority of the tire systems in use are clinchers, due to the relative simplicity of repairs and wide availability of replacement inner tubes.
Most of bicycle inner tubes are torus-shaped balloons while some are not. For example, inner tubes in bicycles of the Moscow bike-sharing service are simply rubber tubes long enough to be coiled and inserted into a tire.
Tubeless.
Tubeless tires are primarily used on mountain bikes due to their ability to use low air pressure for better traction without getting pinch flats. Tubeless tires work similarly to clinchers in that the bead of the tire is specifically designed to interlock into a corresponding tubeless rim, but without an inner tube. Air is inflated directly into the tire, and once "locked" into the rim, the system is airtight. Liquid sealants are often injected into tubeless tires to improve sealing and to stop leaks caused by punctures. An advantage is that pinch flats are less common in a tubeless setup because they require a hole through the tire carcass, not just the inner tube. A disadvantage is that air can escape if the bead lock is compromised from too much lateral force on the tire or deformation of the rim/tire due to hard impact with an object.
Tubeless tires require tubeless-compatible rims, which do not allow air to escape where the spokes connect and have a different shape groove for the tire bead to seat.
Road tubeless.
In 2006, Shimano and Hutchinson introduced a tubeless system for road bicycles. Tubeless tires have not yet gained popular acceptance in road racing due to lack of sponsorship, the tradition of using tubular tires and the fact that, even without the inner tube, the combined weight of tubeless rims and tires is more than top-of-the-line tubular tire wheelsets. Road tubeless is gaining popularity among riders for whom the benefits are worth the costs. Road tubeless tires tend to be a much tighter fit than traditional clincher tires, which makes mounting and removing the tire more difficult.
Airless tires.
Airless were used before pneumatic tires were developed, appearing on velocipedes by 1869. They continue to be developed in an effort to solve the problem of losing air pressure, either from a puncture or from permeability. Modern examples of airless tires for bicycles include BriTek's Energy Return Wheel, an airless bicycle tire from Bridgestone, 
the tire pictured to the right on a Mobike, and solid tires discussed below.
Although modern airless tires are better than early ones, most give a rough ride and may damage the wheel or bicycle.
Solid.
The most common form of airless tire is simply the solid tire. Besides solid rubber, solid tires made of polyurethane or microcellular foam are also offered for 100% flat prevention. Much of the desirable suspension quality of the pneumatic tire is lost, however, and ride quality suffers.
Many bicycle-sharing systems use these tires to reduce maintenance, and examples of solid tires include those available from Greentyre, Puncture Proof Tyres Ltd, KIK-Reifen, Tannus, Hutchinson, and Specialized.
Construction.
Bicycle tires consist of a rubber-impregnated cloth casing, also called the carcass, with additional rubber, called the tread, on the surface that contacts the road. In the case of clinchers, the casing wraps around two beads, one on each edge.
Casing.
Bicycle tire casing is made of cloth, usually nylon, though cotton and silk have also been used. The casing provides the resistance against stretching necessary to contain the internal air pressure while remaining flexible enough to conform to the ground surface. The thread count of the cloth affects the weight and performance of the tire, and high thread counts improve ride quality and reduce rolling resistance at the expense of durability and puncture resistance.
Bias ply.
The fibers of the cloth in most bicycle tires are not woven together, but kept in separate plies so that they can move more freely to reduce wear and rolling resistance. They are also usually oriented diagonally, forming bias plies.
Radial ply.
Radial ply has been attempted, and examples include Panasonic in the 1980s and the Maxxis in the 2010s, but often found to provide undesirable handling characteristics.
Tread.
The tread is the part of the tire that contacts the ground to provide grip and protect the casing from ware.
The tread is made of natural and synthetic rubber that often includes fillers such as carbon black, which gives it its characteristic color, and silica. The type and amount of filler is selected based on characteristics such as wear, traction (wet and dry), rolling resistance, and cost. Oils and lubricants may be added as softeners. Sulphur and zinc oxide facilitate vulcanization. Some tires have a dual-compound tread that is tougher in the middle and grippier on the edges. Many modern tires are available with treads in a variety or combination of colors. Road racing tires with different tread compounds for the front and rear have been developed, thereby attempting to provide more traction in front and less rolling resistance in the rear.
Treads fall somewhere along the spectrum from smooth or slick to knobby. Smooth treads are intended for on-road use, where a tread pattern offers little to no improvement in traction. However, many otherwise slick tires have a light tread pattern, due to the common belief that a slick tire will be slippery in wet conditions. Knobby treads are intended for off-road use, where the tread texture can help improve traction on soft surfaces. Many treads are omnidirectional—the tire can be installed in either orientation—but some are unidirectional and designed to be oriented in a specific direction. Some tires, especially for mountain bikes, have a tread which is intended either for the front wheel or the rear wheel. A special tread pattern, with small dimples, has been developed to reduce air drag.
The profile of the tread is usually circular, matching the shape of the casing inside it and allowing the tire to roll to the side as the bicycle leans for turning or balancing. More-squared profiles are sometimes used on mountain bike tires and novelty tires designed to look like automotive racing slicks, as on wheelie bikes.
Bead.
The bead of clincher tires must be made of a material that will stretch very little to prevent the tire from expanding off of the rim under internal air pressure.
Steel wire beads are used on inexpensive tires. Though they cannot be folded, they can often be twisted into three smaller hoops.
Kevlar beads are used on expensive tires, and these are also called "foldable". They should not be used on straight sidewall rims as they may blow off the rim.
Sidewall.
The sidewall of the casing, the part not intended to contact the ground, may receive one of several treatments.
Tires with sidewalls made of natural rubber are called "gum wall". The tan colored, natural rubber lacks carbon black to decrease rolling resistance, as its added wear resistance isn't needed in the sidewall.
Tires with very little rubber, if any, covering the sidewall are called "skin wall". This reduces rolling resistance by reducing sidewall stiffness at the cost of reducing damage protection.
Variations.
Puncture resistance.
Some tires include an extra layer between the tread and the casing (as shown in the cross section pictured above) to help prevent punctures either by being tough or simply by being thick. These extra layers are usually associated with higher rolling resistance.
Studs.
Metal studs may be embedded in the tread of knobby tires to improve traction on ice. Inexpensive studded tires use steel studs, while pricier tires use more durable carbide studs. A studded, knobby tread that zips onto a smoother, non-studded tire has been developed to ease the transition between the two types of tires.
Reflective.
Some tires have a reflective strip on their sidewalls to improve visibility at night. Others have reflective material embedded in the tread.
Aerodynamics.
In addition to the dimple tread pattern mentioned above, at least one tire has an extra "wing" to cover the gap between the tire sidewall and the wheel rim and reduce drag.
Indoor use.
At least one modern bicycle tire has been designed specifically for indoor use on rollers or trainers. It minimizes excessive wear that traditional tires experience in this environment and is not suitable for use on pavement.
Different front and rear.
Besides the different tread patterns available on some mountain bike tires mentioned above, front and rear tire sets are available for road bikes with different tread patterns, tread compounds, and sizes for the front and rear wheels. Other scenarios involve replacing a damaged tire, and leaving the other one unchanged.
Self inflating.
Bicycle tires have been developed that pump themselves up as they roll forward.
Modular.
Bicycle tires have been developed so that different treads can be zipped on and off. This allows having the additional traction of studded tires only when necessary and avoiding the additional rolling resistance otherwise.
Parameters.
Sizes.
The modern tire-size designations (e.g. "37-622", also known as ETRTO) are defined by international standard ISO 5775, along with corresponding rim size designations (e.g., "622×19C"). Older English (inch, e.g. "28 x 1 ⅝ x 1 ⅜") and French (metric, e.g. "700x35C") designations are also still used, but can be ambiguous. The diameter of the tire must match the diameter of the rim, but the width of the tire only has to be in the range of widths appropriate for the width of the rim, while also not exceeding the clearances allowed by the frame, brakes, and any accessories such as fenders. Diameters vary from a large 910 mm, for touring unicycles, to a small 125 mm, for roller skiing. Widths vary from a narrow 18 mm to a wide 119 mm for the Surly Big Fat Larry.
Lightweight tires.
Lightweight tires range in size from wide.
Middleweight or Demi-balloon tires.
Middleweight or Demi-balloon tires range in size from wide.
Balloon tires.
A balloon tire is a type of wide, large-volume, low-pressure tire that first appeared on cruiser bicycles in the US in the 1930s. They are typically wide.
In the 1960s Raleigh made its small-wheeled RSW 16 with balloon tires so it would have a soft ride like the fully suspended Moulton Bicycle. Other manufacturers then used the same idea for their own small wheelers. Examples include the Stanningley (UK)-made Bootie Folding Bicycle, the Co-operative Wholesale Society (CWS) Commuter, and the Trusty Spacemaster.
Plus-size tires.
A plus-size tire has a width of typically . Three bead seat diameters are available: 559 mm for 26+, 584 mm for 27.5+ (650B+), and 622 mm for 29+. They fill the gap between balloon and fat tires.
Fat tires.
A fat tire is a type of wide oversized bicycle tire, typically or larger and rims or wider, designed for low ground pressure to allow riding on soft unstable terrain, such as snow, sand, bogs, and mud.
Since the 1980s, fat tires of width , and diameters similar to conventional bicycle wheels, have been used on "fatbikes" and all-terrain bikes designed for riding in snow and sand.
Inflation pressure.
The inflation pressure of bicycle tires ranges from for fat bike tires in snow to for tubular track racing tires.
The maximum pressure rating of tires is usually stamped on the sidewall, indicated as "Maximum Pressure", or "Inflate to ..." or sometimes expressed as a range like "". Decreasing pressure tends to increase traction and make the ride more comfortable while increasing pressure tends to make the ride more efficient and decreases the chances of getting pinch flats.
One published guideline for clincher inflation pressure is to pick the value for each wheel that produces a 15% reduction in the distance between the wheel rim and the ground when loaded (i.e. with the rider and cargo) compared to when unloaded. Pressures below this leads to increased rolling resistance and likelihood of pinch-flats. Pressures above this leads to less rolling resistance in the tire itself but to larger total energy dissipation caused by passing vibrations to the bike and especially the rider, which experience elastic hysterisis.<ref>