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Bike Tire Glossary

October 18, 2018

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Bike Tire Glossary

An interactive list of common terms found on TreadBikely.com, along with their down-to-earth explanations. These are also highlighted in columns, articles, and guides throughout the website, which you can view by clicking on the hyperlinked word.

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  • 12-inch
    A wheel/tire size generally suitable for children 2-4 years old. The International Bicycle Fund recommends an inseam of 14-17 inches (35-42 cm). Typically found on small balance bikes, such as Striders.

  • 1

  • 14-inch
    A wheel/tire size generally suitable for children 4-6 years old. The International Bicycle Fund recommends an inseam of 10-20 inches (40-50 cm).

  • 16-inch
    317 mm – 349 mm, depending on the model. A wheel/tire size generally suitable for children 5-8 years old. The International Bicycle Fund recommends an inseam of 18-22 inches (45-55 cm).

  • 18-inch
    400 mm. A wheel/tire size generally suitable for children 6-9 years old. The International Bicycle Fund recommends an inseam of 20-4 inches (50-60 cm).

  • 2

  • 20-inch
    406 mm. A wheel/tire size generally suitable for children 7-10 years old. The International Bicycle Fund recommends an inseam of 22-25 inches (55-63 cm).

  • 24-inch
    507 mm. A wheel/tire size generally suitable for children 9 years of age and older. The International Bicycle Fund recommends an inseam of at least 24-28 inches (60-72 cm).

  • 26-inch
    559 mm. A wheel/tire size that’s been around for more than 100 years. In more recent times, it’s largely found on cruisers, hybrid comfort designs, and budget-oriented department store models.

  • 27.5
    584 mm. This tire size has become popular not just on mountain bikes, but also gravel, adventure, and bikepacking models. Although it’s often referred to as an ‘in-between’ size, this size--also known as '650B'--is much closer to 26” (+25 mm) than to a 29” (-38 mm) version.

  • 29-inch
    622 mm. Also called a 29er, the larger circumference of these tires allows mountain bikers to roll over obstacles more easily, although they can negatively impact turning radius.

  • 7

  • 700C
    622 mm. The same diameter as a 29” wheel, but often narrower and typically only used in reference to a road (cyclocross, gravel, touring, etc.) bike.

  • a

  • Air Bleed System
    Lezyne's proprietary ABS (Air Bleed System) and ABS2 nozzles quickly unscrew from the chuck and  flip to accommodate both Schrader and Presta valves.

  • Aerodynamics
    Like any other component, bike tires create drag—in this instance, based on factors like width and tread pattern. Depending on the end use (mountain bike vs. time trials, for example) manufacturers design their tire profiles to maximize aerodynamics.

  • Air Bleed Valve
    A mechanism (often a button) that allows trapped air to quickly escape the pump’s barrel, without disengaging the chuck and manually releasing by hand.

  • Air Pressure
    The weight of air molecules pressing against the inside of a bike tire, typically measured in pounds per square inch (PSI).

  • Anti-Tack Compounds
    Ingredients like metallic stearate, stearic acid, mica, talc, or other water-based formulas that help prevent sticking. Especially useful after rubber is wound onto spools during the manufacturing process.

  • Antidegradants
    A class of ingredients that helps prevent degradation, such as antioxidants (protect against oxidation) and antiozonants (safeguard against ozone), as well as those that effectively dissipate heat.

  • Aramid
    The technical term for Kevlar.

  • Aromatic Amines
    Organic compounds generated as byproducts of other industrial manufacturing processes, such as plastics and chemicals. Used in the rubber industry to help prolong usable life.

  • b

  • Banbury Mixer
    An internal mixer model commonly used at the beginning of the tire manufacturing process to blend rubber bales with other ingredients.

  • Bar
    A metric measurement of pressure. One bar is equivalent to about 14.5 pounds per square inch (PSI).

  • Barrel
    The largest part of a bike pump, which houses the piston, plunger, and trapped air.

  • Beads
    Rings of tightly-wound steel or Kevlar fibers, which are folded into each side of a tire’s casing to form ends. When the tire is inflated, these beads hold it firmly in place against special grooves in the rim.

  • Books
    Large, industrial cases that store rubber slap until it’s ready for use during the tire manufacturing process.

  • Boyle’s Law
    Simple version: The more air you add to a bike tire, the harder you’ll have to work to pump. Detailed version: At a fixed temperature, the volume of a gas is inversely proportional to the pressure exerted by the gas (expressed as P1 X V1 = P2 X V2).

  • Branding
    Near the end of the manufacturing process, hot metal plates bond ink to the tire’s sidewalls based on the company's specific design.

  • Butyl / Halogenated Rubber
    A synthetic, chemically inert, weather-resistant rubber made by polymerizing isobutylene and isoprene.

  • c

  • Calendering
    As relates to bike tires, this is the the process whereby fiber mesh and casing rubber are permanently bonded by sending each through hot rollers.

  • Carbon Black
    A fine carbon powder created by burning hydrocarbons in insufficient air. In bike tires, it’s used for strength, reinforcement, traction, abrasion resistance, and color.

  • Carbon Dioxide
    An inert gas that’s compressed into small cartridges. When attached to the appropriate nozzle and affixed to a tire valve, it's quickly released to re-inflate a flat.  CO2 is soluble with butyl rubber, so it will leak faster from tires than oxygen.

  • Carcass
    Fabric mesh that's arranged in layers of parallel threads, and then permanently joined with a thin layer of rubber at a 45-degree angle. Once sandwiched between each bead, this carcass (or casing) establishes the tire's shape, acts as its backbone, and determines many of its ride qualities.

  • Chalk
    A filler conventionally used during the bike tire manufacturing process to help define traits like elasticity and strength.

  • Chuck
    The part of the pump that attaches to a tire’s valve and allows air to enter. Also commonly referred to as the nozzle or head.

  • Clincher
    The most commonly used type of bike tire. Once inflated, the tire’s beads ‘clinch’ against the walls of the rim and lock everything into place.

  • CO2 Cartridge
    Available in threaded and threadless versions, these attach to special nozzles that help swiftly re-inflate bike tires via a quick shot of carbon dioxide.

  • CO2 Inflator
    A nozzle that attaches to a CO2 cartridge at one end. At the other end, it fastens to and a tire valve and allows carbon dioxide to enter for fast inflation.

  • Conditioner
    A chemical or other component that helps protect a tire’s rubber against ozone damage, prevent oxidation, and restore suppleness. Ingredients vary depending on each manufacturer's formulation.

  • Coupler
    A small part that connects the rubber hose on a bike pump to its base, barrel, or nozzle.

  • Crude Oil
    The base ingredient for synthetic rubber.

  • Cup
    A part attached to a CO2 inflator that holds, or ‘cups,’ the cartridge to ensure a tight seal and prevent exposing skin to cold temperatures.

  • Curatives
    Common curatives used in the bike tire manufacturing process include carbon black and silica, which define traits like strength and traction, as well as flexibility and wet weather performance, respectively.

  • d

  • Diameter
    The size of a wheel when measured from one sidewall to another. This same measurement is referred to as ‘width’ when it comes to tires.

  • Die
    During the manufacturing process, a tire’s tread rubber is forced through a specially-cut die, which causes it to form a profile that’s thicker in the center and thinner on the sides. This helps improve wear resistance and lengthens the tire’s lifespan.

  • Drum
    A key component of a Tire Building Machine.

  • Dunlop Valve
    A valve type (also referred to as an English or Woods valve) that’s not common in the U.S., but is popular in areas of Europe and Asia. Its design is wide like a Schrader valve, although it will inflate using a Presta-compatible nozzle.

  • Durometer
    An industrial instrument that measures the hardness of polymers like plastic and rubber.

  • Dust Cap
    A part that’s used to prevent dust and other debris from entering the inlet located at the tip of a pump’s nozzle and reducing its performance.

  • e

  • Ends Per Inch (EPI)
    Another common term for Threads Per Inch (TPI).

  • ETRTO
    An acronym for the European Tyre and Rim Technical Organisation.

  • f

  • Fat (Phat) Tires
    Large, balloon-like tires between 3.7” and 5.2” wide, which are mounted to rims ranging in width from 50 mm to 100 mm. Their large volume means they can be ridden at lower pressures and are ideal for soft terrain that shifts quickly, like snow, sand, and mud.

  • Fillers
    Carbon black and silica are two of the most common fillers used in rubber formulations, which cumulatively impact characteristics like softness, strength, traction, resistance to wear, flexibility, and wet weather performance.

  • Floor Pump
    The largest bike pump model available. Features a large, upright barrel attached to a wide base. A flexible rubber hose extends from this base for improved reach and maneuverability, with a wide t-handle on top for maximum leverage. Most models utilize a pressure gauge.

  • Frame Pump
    The largest portable bike pump available. It uses a concave rubber ‘foot’ at each end to wedge itself firmly between a frame's tubing. They pump quickly, but they're not ideal for high-pressure applications. Gauges are uncommon.

  • g

  • Gauge
    A device that displays a tire's air pressure, as measured in pounds per square inch (PSI). The two most common styles are needle-based (chronograph) and digital.

  • Glue
    When it comes to bicycles, this can reference either 1) glue used to attach a patch to an inner tube, or 2) adhesive that adheres tubular tires to special rims.

  • Green Tire
    A ‘green’ tire is one that has completed the assembly process, but hasn’t been branded or vulcanized.

  • Grooving
    When heated during the vulcanization process, negative impressions in a mold press into the tire’s tread rubber, creating grooves that can improve traction.

  • Gum Wall
    A term that references tire sidewalls made from natural rubber, which contain no carbon black. A softer composition creates less rolling resistance, but is also more susceptible to ozone damage and faster decomposition.

  • h

  • Hevea Brasiliensis
    The tree from which a latex is extracted to create natural rubber. As such, it’s colloquially known as the rubber tree.

  • Hose
    The flexible part that extends between a pump’s barrel and its nozzle. Hoses are most common on floor, mini, and micro pumps. Length can vary considerably.

  • Hysteresis
    The process whereby heat is generated from the constant flexing and un-flexing of a bike tire’s casing, causing energy loss.

  • i

  • Inner Tube
    A circular, balloon-like cylinder made from rubber that features a Presta or Schrader valve on one side. Once this valve is attached to a pump and air is introduced, the inner tube expands and presses the tire's beads against the rim. This air pressure also helps soften overall ride quality.

  • International Standards Organization (ISO)
    Based in Geneva, Switzerland, this independent, non-governmental organization helps formulate international standards that create efficiency, safety, and quality among manufacturers. One of these standards is bike wheel and tire sizing.

  • k

  • Kevlar
    Ultra-strong fibers made from a chemical called Poly(p-phenylene terephthalamide), which boast a high tensile strength-to-weight ratio and is five times stronger than steel. Often used when creating the tire’s bead, as well as the casing’s mesh. A secondary rubber/Kevlar strip is often also(...)

  • Knobby
    A term that references large blocks—or knobs—of tread, which help off-road tires improve grip. As with any tread pattern, the rubber compound used in knobbies, as well as their height and spacing, can have a significant impact on performance characteristics.

  • m

  • Metallic Stearate
    A form of stearic acid used to prevent rubber from sticking during the manufacturing process.

  • Mica
    An anti-tack compound used during the tire manufacturing process.

  • Micro (Mini) Pump
    The smallest bike pump versions. They're designed to go just about anywhere, whether in a pocket or strapped to your bike. Many feature hoses and gauges, although they offer the lowest volume-per-stroke.

  • Mold
    As relates to bike tires, this references a metal cavity that's housed inside the shell-like vulcanization chamber. Once the chamber is heated, and the rubber softens, the mold's negative impression leaves behind grooving in the tread for improved traction.

  • o

  • O-Ring
    A small rubber circle located inside a pump’s chuck (and potentially other parts) that helps ensure a tight seal and prevents air from escaping.

  • Orange Seal
    An eco-friendly tubeless sealant brand that promises to adhere to a tire’s rubber, plug large punctures up to ¼”, and last up to 3X longer than competitors. Some of their products include a handy injector system and dipstick at no extra cost.

  • Oxidation
    The moving of electrons from one molecule, atom, or ion to another, which can create a chain reaction that results in chemical changes. When it comes to bike tire rubber, this is often closely associated with sunlight exposure.

  • Ozone
    An odorless, colorless gas formed by electrical discharges or ultraviolet light that’s comprised of three oxygen molecules. This toxic gas breaks down the double bonds found in a tire’s rubber, causing cracks to form on the surface.

  • p

  • Paraffin
    A wax commonly added during the mixing process to protect a tire’s rubber against damage caused by ozone.

  • Patch
    Small rubber circles applied on top of inner tube punctures. A special glue causes near-instant vulcanization (in most instances) to help ensure a complete seal.

  • Pigment
    Carbon black is the most common pigment (among other things) used during the manufacturing process, which provides a dark color.

  • Piston
    A long, slender shaft that runs through the center of a bike pump's barrel and attaches to a t-handle at the top. When the piston goes up, it draws air into the barrel through a valve. When it goes down, the air is forced out through the nozzle. Also commonly referred to as the plunger.

  • Plus Size
    A tire size that bridges the gap between standard mountain bike widths, and those associated with fat bikes. These typically range somewhere between 2.6” and 3.2”.

  • Polybutadiene Rubber
    A type of synthetic rubber known for its abrasion resistance, heat tolerance, and cracking protection. Includes styrene-butadiene rubber (SBR).

  • Polymer
    aka, Rubber.

  • Pounds Per Square Inch (PSI)
    A measurement of the pressure applied to the inside walls of a tire or inner tube.

  • Pressurization Test
    A quality assurance test whereby a bike tire is inflated in a controlled environment until it bursts or pops off the rim. Different tires can have different pressurization requirements, depending on the manufacturer's specifications.

  • Presta Valve
    Long, thin valves that allow for smaller rim holes. Instead of an internal spring, they use a lock nut at the end to ensure closure, which means they’re easier to inflate than a Schrader valve. In many instances, their cores are removable for quickly replacing sealant in tubeless tire setups.

  • Profile
    The aerodynamics of a tire’s sidewalls.

  • Puncture
    A hole or tear that damages a tire to the point where it can no longer hold air. Depending on the scope of the damage, air loss can occur immediately or over the course of several hours.

  • Puncture Resistance Test
    A controlled-environment quality assurance test where sharp metal studs are pressed against a tire until a puncture appears.

  • r

  • Removable Core
    These unthread from the center of a valve (usually Presta) and leave behind a hollow shell. They're indispensable for adding sealant to a tubeless setup, without having to unseat the tire's bead.

  • Rim Tape
    A slim piece of cloth, vinyl, rubber, or plastic 'tape' that lightly adheres to a rim between each flange and protects the inner tube from spoke and spoke-hole punctures.

  • Rolling Resistance
    The friction—and subsequent resistance—that occurs when a tire rolls over any surface. Tread thickness, tire diameter, rubber compound, the presence of extra puncture protection, and inflation pressure are just a few factors that can impact resistance.

  • Rotational Mass
    Newton's second law, which measures the difficulty of placing an object into rotation, or to stopping it from rotating once it’s started.

  • Rubber
    Bales of natural rubber are formed from the Hevea Brasiliensis tree, whereas synthetic rubber comes from crude oil polymers, many of which are also used in the plastics industry. These rubbers are combined at specific ratios in large, industrial mixers with other ingredients like fillers,(...)

  • s

  • Schrader Valve
    The most common valve type found on bicycles and motor vehicles. It uses an internal spring that automatically closes and prevents air leakage, and also features a wider diameter and more robust construction than a Presta valve.

  • Sealant
    Tire sealant contains compounds that remain suspended in liquid under normal riding conditions, but solidify when subjected to mechanical force as they exit the puncture in a bike tire. This clogs the hole and quickly recreates an airtight environment.

  • Sew-Up
    Another term for a tubular tire.

  • Shear Force
    Perpendicular force applied to tread rubber as it's sent through a die. This creates a profile that’s thicker in the center and thinner on the sides.

  • Sidewall
    The side of a tire. It can be made from tan-colored natural rubber, or from rubber that contains carbon black. Although it doesn’t touch the ground, the sidewall’s flexibility has a significant impact on a tire's ride characteristics.

  • Silica
    An ingredient added during the rubber mixing process that acts as a filler and softener.

  • Skin Wall
    Outdated. See Tan Wall.

  • Skinny
    A slang term for a road-oriented tire, which is typically narrower (i.e., ‘skinnier’) than comfort or mountain bike versions.

  • Slicks
    Tires that feature no perceptible tread pattern. This decreases rolling resistance but reduces traction, especially in wet weather situations.

  • Softeners
    Components used to soften and increase rubber pliability, including macro and micro synthetic crystalline waxes, oils, aromatic amines, zinc oxide, along with a variety of pigments and dyes.

  • Spool
    One part of an industrial tire building machine. Also referred to as the drum.

  • Stan's NoTubes
    A popular tubeless sealant brand made from environmentally safe materials that promises to remain liquid for two to seven months, resist freezing temperatures down to -30°F, and seal punctures up to ¼”.

  • Stearic Acid
    An anti-tack ingredient that acts as a lubricant during the tire manufacturing process, and as a rendering agent for zinc oxide.

  • Steel Fiber
    One of several popular materials that's twisted together, wound into rings and then used to construct a bike tire's beads.

  • Stem
    A shortened term for valve stem.

  • Studs
    Metal tips of different sizes and designs, which are screwed into the tread of stud-ready tires. Drastically improves traction in ice conditions. Most often, these are us on large volume (‘plus’ or ‘fat’ size) tires.

  • Sub-Tread
    An additional layer of rubber placed directly underneath the tire’s tread for extra puncture protection. Often reinforced with nylon fibers.  

  • Sulfur
    A key ingredient used during the vulcanization process to transform a ‘green’ tire into one that’s ready for distribution.

  • Suppleness
    A term that references a bike tire’s flexibility, which directly impacts traits like cushioning, rolling resistance, and cornering ability.

  • t

  • T-Handle
    The uppermost portion of a frame (aka, track) pump, which attaches to the piston. This is where users place their hands when moving in up-and-down strokes.

  • Talc
    An anti-tack compound used during the tire manufacturing process.

  • Tan Wall
    A tire that contains a minimal amount of rubber in its sidewalls. Like a gum wall, this is aimed at decreasing weight and improving rolling resistance. Note: The terms ‘tan wall’ and ‘gum wall’ reference two different construction methods, and are not interchangeable.

  • Threading
    The mesh yarn bonded with a tire’s carcass. Made from threads of twisted Kevlar, nylon, or other textile fibers.

  • Threads Per Inch (TPI)
    The number of threads contained in one square inch of a tire's casing. Lower TPI tires typically feature greater weight and rigidity. Higher TPI tires are often lighter and suppler.

  • Tire Building Machine
    When it comes to bike tires, this involves A large drum or spool that expands and contracts as needed to help fold a bike tire's tread rubber over its wire beads. It's also useful when applying protective sub-tread.

  • Tire Groover
    A device with a sharp, heated tip that's used to manually groove tread into the surface of a tire. Infrequently used in cycling.

  • Tire Iron
    Another term for a tire lever.

  • Tire Lever
    A portable plastic lever used to unseat a tire’s bead from the rim when replacing a punctured inner tube. Frequently also referred to as a ‘tire iron.’

  • Torus
    The shape created by an inner tube when it’s inflated; like a thin doughnut.

  • Track Pump
    Another name for a floor pump.

  • Traction
    The ability of a bike tire to grip a specific surface. Rubber formulations are often different, depending on whether this surface is asphalt, gravel, hard-packed dirt, loose soil, and so forth.

  • Tread
    The part of the tire that comes into direct contact with the ground.

  • Tread Pattern
    Grooves formed in a tire’s tread during vulcanization by the mold's negative impression.

  • Tread Wear Test
    A quality assurance test that involves simulating road wear by spinning a tire against a metal wheel for thousands of miles. Other versions feature large bumps that replicate hitting a curb thousands of times in a row.

  • Tube
    A shortened term for an inner tube.

  • Tubeless
    Instead of an inner tube, this setup uses a specially formulated liquid to quickly seal small tire punctures as they occur. Popular brands include Orange Seal and Stan’s NoTubes.

  • Tubular
    A tire that's stitched around an inner tube and then glued to a specially designed rim. Often lighter and less expensive than clincher tires.

  • v

  • Valve Gasket
    A small piece of rubber that seals the junction between a pump’s nozzle and a tire’s valve.

  • Valve Stem
    A simple device that uses a removable core, which is housed inside an elongated body, to seal air inside a bike tire or inner tube. Presta and Schrader are the most common types of bike tire valve stems.

  • Volume-Per-Stroke
    The air volume that a pump's barrel can hold. Measured in cubic centimeters (cc).

  • Vulcanization
    Also commonly referred to as 'curing.' A process whereby a ‘green’ tire is heated to high-temperatures inside a clamshell-like mold, which causes all of its layers to fuse at a molecular level. This chemical change hardens the rubber, while also providing the elasticity needed for real-world use.

  • w

  • Wax
    Common versions added during the bike tire manufacturing process include macro and microcrystalline waxes, synthetic (petroleum) waxes, and paraffin waxes. With regular use, these migrate to a tire’s surface and help protect the rubber against ozone damage.

  • Width
    The size of a tire when measured from one sidewall to another. This same measurement is referred to as ‘diameter’ when it comes to wheels.

  • z

  • Zinc Oxide
    A key ingredient used during the rubber vulcanization process. Also acts as a preservative, antifungal agent, and UV protectant.

Derek is an avid cyclist with more than two decades of experience in the sport, and currently resides in Denver, Colorado. He enjoys all types, including road, MTB, cyclocross/gravel, commuting, and touring. When he's not writing reviews and guides related to bike accessories, parts, and gear for TreadBikely.com, he's riding, talking about cycling, or thinking about bikes he can't afford. #rolloutblissout
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