Electric Bike (Ebike) Encyclopedia

When shopping for a conventional or electric bike, we often are faced with a bunch of new terms describing the different parts of the bike. Sure, we all know what a handlebar is, and we can take an educated guess as to the meaning seat post, but when it comes to other parts, we're stumped. And ebikes have changed a lot over the years.

So we put together this alphabetical list of common terms used to describe various bicycle components.

1) Axle: A rod that attaches the wheel the a bicycle and provides support for bearings on which the wheel rotates. Some axles use bolts and washers to connect to the dropout portion of the frame or fork, while others offer quick release connections.

2) Battery: The power source for an ebike and typically comprised of multiple battery cells to equal a determined voltage. Major manufacturers include Samsung, LG and Panasonic. The most common types of ebike batteries have lithium-ion chemistry, and are mounted on (or integrated into) the downtube, or attached to the rear rack. To learn more about ebike batteries, check out our Electric Bike Battery FAQ.

3) Battery Charger: The battery charger draws electric power from a wall outlet or solar array, and plugs into the battery to charge it. A battery management system distributes the charge to each individual battery cell. Smart chargers detect when the batteries are fully charged and discontinue powering when the optimum voltage is achieved.

4) Bearing: A device that facilitates rotation using small round balls or cylinders between 2 surfaces, thereby reducing friction. Bearings are found on a bicycle's bottom bracket, headset, and axles.

5) Bell: An audible device for warning pedestrians and other cyclists. 

6) Belt-Drive: An alternative to a steel chain, belt drives are typically made of highly durable carbon fiber material and do not require grease or other lubricants.

7) Battery Management System (BMS): The electronic system that manages a rechargeable battery. It protects the battery from operating outside its safe operating range, controlling its environment by limiting the charge and discharge of the battery. The BMS may also store and communicate data, authenticate the battery and balance the cells when charging.

8) Bottle cage: A water bottle holder attached to the frame using brazons or bosses.

9) Bottom bracket (frame – shell): Frame member – the bottom bracket (shell) is the frame component found at the end of the seat tube, down tube and chain stays. It holds the bottom bracket bearing set that mount’s the bicycle’s crankset (where the pedals/crank arms connect to the bike).

10) Bottom bracket (component): The bearing system that the pedals (and cranks) rotate around. Contains a spindle to which the crankset is attached and the bearings themselves. The bottom bracket fits inside the bottom bracket shell, which is part of the bicycle frame.

11) Brakes: Devices used to stop or slow down a bicycle. Brakes can be mechanical (where a cable is pulled by a brake level to actuate the brake), or hydraulic (where a pull of the brake lever changes the hydraulic fluid pressures in a line connected to the brake). The braking mechanism can be a caliper or V style, which causes rubber brake pads to grip the rim of the wheel, or or rotor style, where the caliper grips a rotor disc connected to the wheel. Conventional bikes also have coaster brakes, which stop rear wheel rotation by reverse pedal action.

12) Brake Levers: Levers on the handlebar for actuating a bicycle brake system. Mechanical brake levers pull a cable to actuate the brakes. Hydraulic brake levers force hydraulic fluid through a hose to push the piston of a caliper out.

13) Braze-Ons (aka Bosses): A fitting protruding from a frame to provide attachment, typically for cable housings, tire pumps, racks and similar accessories.

14) Cable Guides: Fittings on the frame which manages and guides derailleur or brake cables and housings.

15) Cable: A metal cable enclosed in part by a metal and plastic housing that is used to connect a control, such as a brake or shifting lever, to the device it activates.

16) Cartridge Bearing: A type of protected and self-contained bearing set where roller bearings are sandwiched in between two bearing rings called races. They are not serviceable and must be replaced as a unit. In the case of a headset, the bearing would be pressed into the head tube or head tube cup and the steerer tube would insert through the inner race.

17) Cassette: A group of stacked sprockets (cogset) ranging from a small amount to large amount of chain teeth, thereby adjusting the gear ratios to the rider. The cassette slides onto the rear wheel free hub of a bicycle.

18) Chain: A system of interlinking pins, plates and rollers that transmits power from the front sprocket (chainring) to the rear sprocket (freewheel or cassette). On some newer ebike models, the traditional steel chain is replaced with a carbon belt, which does not require lubricant to operate.

19) Chain Guard: Protective cover for the crankset, designed to keep clothing from becoming entangled in or dirty from contact with the chain. In Dutch style bikes, the chain may be fully enclosed by the chain guard.

20) Chainring: One of the front gears attached to a crank arm set.

21) Chain Stays: A part of the bike frame – a pair of tubes or struts that mount the frame’s bottom bracket to the rear fork ends / dropouts. The chain stays are the part of the frame that run parallel to the chain.

22) Chain Tensioner: An optional device to maintain proper chain tension.

23) Controller: A component often considered the brain of the bicycle. The controller governs the manner of performance from an electric motor. It protects the motor, regulating the speed and torque of the motor. The battery, throttle/pedelec sensor and motor connect to the controller.

24) Crankset: Composed of two crank arms, at least one chainring and optional chain guard. The crankset attaches the bicycle via the bottom bracket.

25) Derailleur: An assembly of levers and gears, usually cable actuated, that moves the chain between sprockets on a cassette/multi-speed freewheel or chainring assembly. The rear derailleur mounts to the frame dropout via the dropout hanger, and the front derailleur mounts to the frame seat tube via a braze on or seat tube clamp.

26) Derailleur hanger: A removable mount attached to the rear frame dropout. The mount serves to attach the derailleur to the frame in a specific position. Removable in case it breaks and avoiding the need to replace the frame.

27) Direct Drive Hub Motor: A hub motor where the axle is the stator of the motor and the hub spins over the stator, floating on two sealed bearings. There is no reduction of gears with rpm of the motor being equal to the rotation of the tire. Advantages are simplistic design, minimal noise, and high wattage. Disadvantages are weight, size, magnetic and resistance. Direct drive motors are also brushless hall sensor motors. Learn more about ebike motors here.

28) Disc Brakes: Brakes where the caliper mounts over a disc rotor attached to the wheel hub. Upon actuating the brake levers, brake pads, one on each side of the rotor are compressed together causing friction against the rotor to slow the bicycle down.

29) Down Tube: A frame member – the tube mounting the head tube (steering) to the bottom bracket shell (crankset). On higher-end ebikes, the battery may be integrated into the downtube for a more aerodynamic and weight-balanced design.

30) Dropouts: A frame’s rear fork end or a front fork end that the wheel axles mount to. Rear dropouts are frame members and mount to the seat and chain stays.

31) Dynamo: Bicycle lighting component, also known as generator.

32) Eyelet (frame): Attachment point on frame, fork, or dropout for fenders, racks, etc. Similar to braze-ons.

33) Eyelet (wheel): A stainless steel grommet protecting a small rim hole in which a spoke nipple passes through the rim so it may attach to a spoke.

34) Fat Tire Electric Bike. A fat tire bike has tires that are at least 4" wide. The tires can be 20", 24" or 26" in diameter. Rear our review of some of the best fat tire electric bikes.

35) Fender: Curved pieces of metal or plastic above the tires which catch and redirect road spray thrown up by the tires, allowing the rider to remain relatively clean.

36) Ferrule: A metal or plastic sleeve used to terminate the end of a cable housing.

37) Folding Hinge: A locking mechanism with a safety latch which when released, will allow the bicycle to fold in half. The hinge is welded to the frame. For more on folding electric bikes, check out our review.

38) Fork: A frame component that integrates a bicycle’s frame to its front wheel and handlebars, allowing steering by virtue of its steerer tube. May be rigid or suspension in design. To learn more about ebike suspension, check out our Ebike Suspension FAQ.

39) Fork End (Dropout): Paired slots on a fork or frame at which the axle of the wheel is attached.

40) Frame: The mechanical core of a bicycle, the frame provides points of attachment for all the various components that make up the completed bicycle. The main parts of the frame include the top tube, head tube, down tube, bottom bracket, seat tube, chain stays, seats stays and rear dropouts.

41) Freehub: A ratcheting assembly attached to a hub or hub motor onto which a cassette is slid on. The freehub allows the bicycle to coast without the pedals turning or pedals turning in reverse and lock when pedaling forward.

42) Freewheel: An assembly that incorporates one or more cogs/sprockets and allows the bicycle to coast without the pedals turning. A freewheel is threaded onto a fixed hub or hub motor and contains the ratcheting system unlike a free hub which is the ratcheting system only.

43) Full suspension: A bicycle that has both a front suspension fork and rear shock. Some bikes also come with suspension seat posts, which allow the seat time move up and down. For more information about full-suspension ebikes, check out our Ebike Suspension FAQ.

44) Geared Hub Motor: A hub motor where the hub is powered through a reduction via planetary gears. The reduction is typically 5-to-1, allowing the motor to spin at a much higher rpm than the hub itself. The higher rpm creates additional torque, thereby reducing the size and weight of the motor when compared to a direct drive motor. Advantages are (slightly) higher torque for hill climbing, free hub spinning (no resistance when pedaling not under power), smaller size and lower weight. Disadvantages are complex planetary gear system (added service issue), noisy (whining sound from gears). Geared hub motors are also brushless hall sensor motors.

45) Grips: A rubber or leather sleeve around the end of the handlebar so as to provide padding and grip for the hands. May include lock rings to lock grips in place.

46) Grip Lock Ring: A ring, usually anodized aluminum, of varying colors, that serves to retain the grip in place via a tightening bolt. This is especially helpful for ergonomic grips, which have are shaped to fit comfortably in the riders hands.

47) Gusset: Plates added to the outside of frame tubes to strengthen joints. These are commonly seen on folding bicycles at the hinge and mountain bicycles at the head tube.

48) Hall Sensors: A 3-phase motor sensor system measuring the motor’s stator position, communicating it back to the controller to spin the motor in the right direction and at the right time for efficiency. Hall sensors allow powering the motor through alternating currents through the stator windings for smooth acceleration.

49) Handlebar: A straight or angled tubular bar, attached to the bike using an intermediary stem, to the steerer tube of the fork. Allows hand steering and provides a point of attachment for controls and accessories.

50) Handlebar Grips: A rubber or leather sleeve around the end of the handlebars so as to provide padding and grip.

51) Hardtail: A bicycle with no rear suspension, typically used to describe mountain bikes.

52) Head Tube: A frame member – the front facing tube that contains the headset and that the fork steerer tube slides through. Mounts to the top tube and down tube.

53) Headset: The bearings that form the interface between the frame and fork steerer tube.

54) Headset Spacer: An aluminum ring sliding over the fork steerer tube, to space the mounting position of the stem. There are typically 4 to 5 spacers equaling 35-40mm of displacement space. The stem can be mounted higher or lower on the steerer tube by placing the spacers underneath or above the stem.

55) Hub: The core of a wheel containing bearings and the axle, whether quick release or solid. The hub has drilled flanges for attachment of the spokes. Typically made of aluminum.

56) Hub Dynamo: A generator inside one of the hubs for powering lights.

57) Hub Motor: An electric motor incorporated in the wheel of an ebike. Hub motors can be used on front wheels, but are more typically found on rear wheels.

58) Hydraulic Disc Brakes: Brakes where the piston’s pushing force is actuated by hydraulic fluid being forced outwards when pulling the brake lever.

59) Inner Tube: A rubber/butyl tube that contains air to inflate a tire. Has a Schrader or Presta valve for inflation and deflation. Comes in various sizes to match the tire’s size.

60) Internal Gear Hub: A gearbox mounted inside the hub. Cable operated by one or two cables. Often used in commuting applications, since it allows gears to be deployed without the use of a greasy derailleur. The Rohloff IGH can be found on the Bakcou Storm Jäger.

61) Kickstand: A folding metal rod attached to the bike, used for assisting a bicycle to stand up on its own. Usually mounts to frame near the bottom bracket, sometimes near rear dropouts. Scissor kick stands use dualroad to create a more stable platform. 

62) Locknut: A nut designed not to loosen due to vibration.

63) Lock Ring: A ring, usually metal, of varying design, that serves to retain a component in place, such as grips.

64) Luggage Carrier: Any accessory equipment designed to carry tools, gear or cargo.

65) Master Link: A bicycle chain accessory that allows convenient removal and reconnection of an installed bicycle chain without the need for a chain tool.

66) Mechanical Disc Brakes: Brakes where the piston’s pushing force is actuated by an arm’s movement when pulling the brake cable via the brake lever.

67) Mid-Drive Motor: A motor system powering an electric bicycle via the crankset. The motor system replaces the bottom bracket and often the crankset itself. Power is applied to the rear wheel, propelling the bike forward via a traditional drivetrain such as a derailleur and cassette gear system or internal gear hub.

68) Nipple: A specialized nut that attaches a spoke to a wheel rim.

69) NuVinci HUB: A continuous variable transmission inside the rear wheel hub that offers seamless shifting via a friction point following the circumference of a ball bearing from center to side. If the friction point is at the center of the ball bearing, where the circumference is largest, it would simulate the larger sprocket of a gear cassette. If the friction point is at the edge/side of the ball bearing, where the circumference is the smallest, it would represent the smaller sprocket in a traditional gear cassette. Imagine the ball bearing as a flat circle, the center is the widest point while the edge is the shortest point and notice how this compares to a gear cassette where sprockets/cogs are aligned from large to small.

70) Open Guides: An open fitting on the frame which guides a derailleur cable, brake cable/hose, or wire harness.

71) Pannier: Zippered storage bags that mount to sides of luggage racks. Pronounced pan-ear, or pan-yer.

72) Pedal: Platform component that mounts to the crank arm and accepts the rider’s force in spinning the crank arm. There are various types such as a folding version.

73) Pedelec: Powering a bicycle via sensors at the bottom bracket / crankset. There are 2 versions, cadence and torque. Cadence are the most basic and considered inefficient, dangerous and low quality unless combined with a wheel rotation sensor. Cadence sensors alone are typically found on inexpensive Chinese eBikes marketed in the USA under various brands. The cadence sensor powers the bicycle based on the rotation of the crankset with no regard for speed or gear position. The Torque sensor is a more efficient system powering the motor according to the amount of force exerted from a rider’s legs onto the pedals. Torque sensors offer a natural and realistic approach to powering an ebike via the crankset.

74) Peg (BMX Only): Short metal tube fastened to one or both ends of the wheel axles to either enable the rider perform certain tricks or provide a place for extra riders to stand or rest.

75) Pivot: An axle or spindle at the center of a rotation or movement. Can be the mount of a V-Brake caliper or spindle/axle at the point of rotation for a rear suspension arm.

76) Quick Release: A skewer with a cam lever on one end that loosens axle when the lever is flipped. Used for releasing wheels and seat posts: see Quick release axle.

77) Quick Release Axle: A wheel axle where a quick release skewer can release a wheel tool free and without completely removing the axle.

78) Rack: A rack that attaches behind the seat, usually with stays to the rear dropouts that serves as a general carrier.

79) Rear shock: A rear suspension shock absorber for a full suspension soft tail bicycle.

80) Reflector: Reflects light to make bicycle evident when the illuminated by headlights of other vehicles. Usually required by law.

81) Rim: That part of a wheel to which the tire is attached and forms part of the braking mechanism in Rim (V) brakes. Rims are typically multi-walled with double or triple walls of aluminum for strength. Walls create a box like construction, increasing the stiffness and durability of the rims.

82) Rim (V) Brakes: Brakes where caliper arms mounted to pivots are squeezed together forcing brake pads to friction against the edge/lip of a wheel’s rim to slow down a bicycle.

83) Rotor: The disc of a disc brake system. The rotor is attached at the hub of a wheel and has 2 pads squeezed on both sides simultaneously to slow down a bicycle.

84) Saddle or Seat: What a bicyclist sits on. There are various styles with wider saddles preferred by riders whom limit their pedaling and prefer added support. Riders who pedal frequently prefer narrow saddles to clear their thigh movement. Short nose saddles are typically women saddles while long nose are mens. Openings or center spacing ease the pressure on the perineum.

85) Saddle rails: The 2 elongated metal rods at the underside of the saddle which mount it to the seat post. The long rails allow for the sliding adjustment from front to back of the saddle before locking into position.

86) Sealed Bearings: A type of protected and self-contained bearing set where roller bearings are sandwiched in between two bearing rings called races. The races are sealed with covers (typically made of a composite or steel) on both sides and remain dirt free. The sealed covers are what differentiates in from cartridge bearings. They are not serviceable and must be replaced as a unit. Deep Groove bearings have deep channeled races allowing for higher radial forces. 

87) Seat clamp: A clamp usually made of aluminum with a locking quick release arm that tightens the frame around the seat post. When open, allows the seat post to slide up and down the frame’s seat tube, adjusting the saddle height.

88) Seat tube: Frame member – the vertical tube running from the seat clamp to the bottom bracket. The seat tube holds the seat post, which adjust up and down for a rider’s height. The seat stays and top tube also mount to the seat tube.

89) Seat Post: A post that the saddle is mounted to. It slides into the frame’s seat tube and is used to adjust the ride height depending how far into the seat tube it is inserted. A seat clamp mounted to the seat tube will lock the seat post in position. The seat post typically incorporates a saddle mount that allows for the adjustment of the saddle from front to back via the saddle’s rails, and rotating the nose up or down before locking the saddle into position.

90) Seat stays: Frame member – a pair of small diameter tubes mounting the top of frame’s seat tube to the rear dropouts.

91) Shifter: A control component mounted to the handlebar which will shift the derailleur into the desired gear.

92) Soft tail: A bicycle with a rear shock.

93) Spindle: An axle around which a pedal rotates; screws into crank arms.

94) Spoke: Connects the wheel rim to the hub. Usually stainless steel wire with one end swaged to form a head and one threaded end. A typical wheel has 36 spokes.

95) Steerer tube: A tube on top of a fork that is inserted through frame and serves as an axle by means of which the bicycle can be steered.

96) Suspension fork: A frame component that integrates a bicycle’s frame to its front wheel and handlebars, allowing steering by virtue of its steerer tube. A suspension fork absorbs compression, limits rebounding and often adjustable. Lock outs, lock out compression. The upper legs are named “stanchions”, the “crown” is the part the stanchions are mounted to. The crown is mounted to the steerer tube.

97) Stem: A component typically made of aluminum and used to attach the handlebars to the steerer tube of a fork. There are threaded and threadless versions of stems. Threaded versions will have a quill (extended arm) that enters into the fork’s steerer tube and adjusts for height via an interior friction bolt. Threadless versions secure over the steerer tube and lock in place by pinch bolts. There are adjustable and folding versions of threaded and threadless stems. Adjustable will allow various angle positions while folding, folds the handle bar sideways to reduce the overall transporting size of the bicycle.

98) Throttle: A control component mounted at the handlebar that either replaces the grip (twist), a portion of the grip (half twist) or next to the grip (thumb). The throttle offers the rider the ability to send a variable signal to the controller to increase or decrease power to the motor.

99) Tire: Mounts to the wheels, usually clincher, requiring the use of air in tubes. Various sizes in diameter and widths.

100) Toe clips: A metal or plastic cage attached to a pedal. Usually has an adjustment strap. Secures foot to pedal for increased control and transfer of power.

101) Top tube: Frame member – the tube mounting the steerer tube to the seat tube.

102) Torque Plates: A stainless steel plate mounted to the rear dropouts of the frame to displace the rotation torque of the motor axle across the dropout and eliminate undue stress to the dropout axle slot itself. The plate’s design mimics the design of the dropout with the slot equaling the axle’s width.

103) Valve stem (or simply valve): Port for adding or releasing air from the inner tube. Two types are commonly used: Presta and Schrader.

104) Wheel: The circular device comprising the rim, hub, spokes, tire, and tube.

105) Wire harness: A group of wires connecting the electrical components of the bicycle.

Addendum

Conversion Kit: An electric bike conversion kit allows you to modify a conventional bike by adding a motor, controller, battery, pedal assist system and throttle. Read more about ebike conversion kits here.