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Glossary of Terms

The following terms are frequently used in documentation from Rad Power Bikes.




Allen wrench


A tool used for tightening and loosening bolts with a hexagonal head that come in a variety of sizes listed described in millimeters (ex: 4 mm Allen wrench). Also called an “Allen key,” “hex key,” or “hex wrench.”

Alternating Current


See “Current”.



Short for “Ampere,” a base unit of electric current.

Amp Hours (Ah)


A standard measure of electric current over time used to describe battery capacity. One amp hour is equal to the amount of energy that passes a given point in one hour.



The component at the center of the hub that connects the wheel to the dropouts of the bike frame. The axle can attach via a quick release mechanism or nut/bolt mechanism that requires tools.

Barrel Adjuster


A component consisting of a hollow bolt that stops the cable housing and can be used to adjust cable tension on derailleur and brake cables.



An energy storage device with components that deliver a specific voltage and current capable of powering an electric motor.

Battery Management System (BMS)


An electronic circuit that optimizes battery output; found on advanced batteries.

Bottom Bracket


A component located at the bottom of the bike frame that contains a spindle to which the crankset attaches and bearings that allow the spindle and cranks to rotate.

Bottom Bracket Spindle


The rotating axle that runs through the bottom bracket connecting each crank/pedal.



A device for slowing or stopping a moving vehicle. On bikes by Rad Power Bikes, the brakes are mechanical disc brakes that use a medal disc rotor near the hub that is squeezed by ceramic brake pads and a caliper when the brake levers are depressed.

Brake Cables


Steel cables encased in protective plastic tubing that transmit pressure exerted on the brake levers to the brake calipers and disc rotor.

Brake Caliper


A bike brake part consisting of two hinged components that squeeze the brake pads onto the disc rotor when the brake levers are depressed.

Brake Levers


The components on the handlebar that are pulled by the rider’s hands to activate the brake caliper and pads to slow the bike.

Brake Pads


A pair of components inside each brake caliper that is pressed against the brake rotor/disc that causes friction and slows down the wheel and bike.

Brake Rotor (aka Brake Disc)


A disc shaped metal component attached to the wheel hub that rotates in between  the brake pads in the brake caliper and the caliper and pads clamp onto when the brake lever is pulled creating friction and slowing the wheel and bike.

Brushless Motor


A motor type that has no wear points other than the bearings and is therefore more mechanically simple, yet more expensive than motors with brushes.



Pedaling rate. Determines whether or not pedal assist is applied.

Cable Pinch Bolt


A mechanism that uses a bolt and washer to secure the end of a derailleur or brake cable.



The sprockets (stacked set of gears or cogs) on the rear wheel. When a rider shifts gears, the derailleur moves the chain to another cog on the cassette.



Loop of linked metal pieces that allows power to transfer from the pedals/front chainring to the rear wheel.



A particular piece comprised of pins, plates, and rollers that links to other pieces to form the chain.



The circular metal disk with teeth that grab the chain links and is revolved by the pedal cranks.



The frame tubing, which runs near and parallel to the chain, connecting the bottom bracket with the rear dropouts.



The sprockets or gears that comprise the cassette.



A bike used for commuting in an urban area.



Plastic or rubber fittings that clip together and allow the electrical components and wiring to be connected and weather resistant.



An electronic circuit or small computer that allows electrical components to communicate and controls the motor.  

Cranks/ crank arms


The arms or levers that connects the pedals to the chainring/bottom bracket.



A rotating part of a bike drivetrain consisting of the front chainring, cranks, and pedals that converts the reciprocating movement of a rider’s legs into rotational motion that moves the chain and rear wheel. The crankset is connected to the bike frame at and by the bottom bracket and connected by the chain to the rear wheel via the cassette.

Crossbar/ cross tube (aka top tube)


The portion of the bike frame that connects the headtube with the seat tube. On a Step-thru model frame, the crosstube slopes down towards the bottom bracket.



A fundamental concept of electricity that describes the movement or flow of an electric charge. Direct Current (DC) flows in one direction with a constant voltage, and is the current delivered by a AA battery, for example. Alternating Current (AC) changes direction and voltage polarity, which is the power supplied by household outlets/power plants.



The moving mechanism that pushes or pulls the chain onto another gear.

Derailleur limit screws


Adjustable screws that limit the high and low ends of the range the derailleur can move, which are used to prevent the chain from falling off the wheel-side and derailleur-side of the cassette.

Direct Current


See “Current”.

Direct Drive Motor


A type of motor that has no gear reduction. On bikes by Rad Power Bikes with this motor, they are capable of regenerative braking and more efficient at higher speeds, and are slightly slower when starting and slightly quieter when riding than a geared-hub motor.



The part of a bike frame that connects the head tube to the bottom bracket.



Part of the frame at the front fork and back of a bike frame that are slotted for the entry of the front or rear wheel axle.



A semicircle of plastic or metal that, when installed, hovers over the front/rear wheel of a bike and blocks water, mud, and other debris from spraying up from the tires onto a rider.



A flat tire/ tube. See also pinch flat and puncture flat.

Flat-Side Cutters


The name of a tool used to snip zip ties, similar to scissors, but characterized by one flat side of the small blade that allows for a cut flush with a flat surface. Also known as flush-side cutters and flat-side nippers.



The front portion of the bike frame to which the front wheel is attached.



This is the metal tubing that connects all of the bike components.



A mechanism using a ratchet and pawl (uni-directional spring loaded clasp) that allows the gear/sprocket to be propelled when a rider pedals forward, but also allows the rear wheel to continue to rotate when a rider stops pedalling or pedals backwards.

Geared Motor


A type of motor that uses a gear reduction inside the motor housing. On bikes by Rad Power Bikes with this motor, they have double the low-end torque, start slightly quicker and more efficiently, are slightly louder, and are less efficient at higher speeds than a direct drive motor.



Metal disks with teeth that grab and revolve the chain. Moving the chain to another disk is changing gears.



The device that allows a rider to steer the front wheel and bike. Comprised of two handles connected by tubing.



A system inside the headtube of the bike that uses ball bearings to allow the handlebars to move and steer the front wheel.

Head Tube


The part of the bike frame in the front that connects the front fork and the handlebars.



The cylinder in the middle of a wheel that is the central point around which the wheel revolves.  

Hub Motor


A motor located at the center of a wheel; in all bikes by Rad Power Bikes the motors are located in the center of the rear wheel by design.

Inner tube


See “Tube.”

LCD Display


The device located at the center of the handlebars that shows the user information including speed, watt output, pedal assist level, and odometer.

Lead Acid (Pb A) Batteries


An older, heavier battery technology used in early model electric vehicles (not used in any bikes by Rad Power Bikes).

Lithium-Ion (Li-ion) Battery


A newer, advanced, rechargeable battery technology that has a high energy density (or level of energy per unit of mass), no memory effect (loss of energy storage capacity over time), and low self-discharge (due to internal reactions without connection to electrodes).



A nut used to secure a threaded part, like the end of a quick release skewer opposite the cam lever, to prevent the part from unthreading or moving.

Mechanical disc brake


A braking system operated by a cable, rather than hydraulic, mechanism.



A low-powered motorcycle that can have pedals; considered a motorized vehicle requiring a license, insurance, and other requirements based on local laws.



The unit of electrical resistance, or the electrical resistance between two points of a conductor when a constant potential difference applied between them produces a current of one amp in the conductor.



The name for a bag designed to attach to your bike and carry cargo.



The component that a rider puts their feet on to propel the bike. The pedals have a letter indicating which side of the bike they install onto and the left pedal is reverse threaded. Reverse threaded means the left pedal tightens onto the crank by counterclockwise rotation.

Pedal Assist (PAS)


A mode of calling up power from an ebike motor and battery that delivers assistance based on sensing a rider’s pedalling. Torque sensors deliver assistance proportional to the pressure or torque a rider delivers when pressing on the pedals, while cadence sensors, which come on all bikes by Rad Power Bikes, deliver assistance based on the cadence or revolutions of the pedals/cranks.  

Phillip’s head screwdriver


A tool used for tightening and loosening screws with a plus sign or “x” head.

Pinch flat


A type of flat caused by the tube being pinched between the rim of the wheel and a hard riding surface. This is more likely to occur when tires are inflated below the recommended tire pressure. When changing this type of flat, the damaged area of the tube may look like one or two parallel lines.



The rate energy is transferred/transformed over time; measured in watts.

Puncture flat


A type of flat caused by a sharp object stabbing the tire and tube. Typical causes are thorns, thistles, sharp rocks, broken glass, tacks, and other sharp objects. Tire liners can help decrease the likelihood of puncture flats happening, but cannot prevent them in all situations.

Quick release


A bolt and cam lever that enables adjustment or removal of parts, like the seat post and front wheel, without requiring tools. To open, unhinge the lever and untwist the bolt as necessary.

Quick release skewer


A cam lever attached to a metal rod that can be inserted to a hollow axle allowing for quick release and removal of the front wheel.



A device that light bounces off of and back towards the source of light, which helps others see bikes and should be attached and visible at all times when bike riding and may be required by law.

Regenerative braking


A method for converting part of the braking energy into a small amount of battery capacity.

Repair stand


A contraption designed to secure a bike, most commonly off the ground, for maintenance activities.

Resistance or rolling resistance


The drag or force resisting the movement of a wheel across a surface. All wheels will eventually slow down due to resistance of moving parts against each other.



The metal ring that holds the tire and is connected to the hub by spokes under tension.

Rim strip


A strip of material on the inside of the rip that protects the inner tube from being punctured by the spoke holes.

Schrader valve


This is a type of pneumatic tire valve that is very common and comes on all tubes sold by Rad Power Bikes.



The component on a bike that holds the majority of a rider’s weight.

Seat post


The metal tube that connects the seat/saddle to the seat tube part of the bike frame.

Seat stay


Frame tubing connecting the top of the seat tube with the rear dropout.

Set screw


A small screw used for making adjustments to brake calipers and brake levers.



A lever for shifting gears that works by transmitting pressure along a cable that moves the derailleur, which then moves the chain onto a different gear.



The component that connects the handlebars to the head tube.



A frame design that allows a rider to mount the bike with a small step in front of the seat rather than swinging a leg over the seat/ back of the bike.

Suspension seat post


This is a seat post that comes equipped with a built-in shock absorbing mechanism that absorbs bumps from the road before they can jostle a rider.



The metal rods that connect the rim to the hub of a bike wheel. These are round 12 gauge stainless steel rods on the wheels that come on bikes by Rad Power Bikes.



A toothed gear or cog that connects into chainlink openings and is part of the cassette.



The part that connects the handlebars to the steerer tube.



A device that allows the rider to manually call up power from the motor and battery without pedaling. On bikes by Rad Power Bikes there is a twist throttle.



The round rubber/fiber casing for the inner tube that connects to the rim and that the wheels roll upon.

Tire bead


A ridge molded on the edge of the tire that keeps the tire attached to the rim when the tube is inflated.

Tube/ inner tube


The circular rubber component that holds air inside the tire around the rim.

Volt (V)


The unit of electromotive force, or the difference of potential that would drive one amp of current against one ohm of resistance.



A fundamental concept of electricity that describes electric potential difference.



A measurement of power, or how much work is done/ the rate that energy is spent over time. One horsepower is about 750 watts.

Watt hour


Equal to one watt operating for one hour; a measurement of energy used to describe battery capacity.



The portion of a bike that includes the rim, spokes, and hub. May also include the motor assembly, cassette, tube, and tire.

Wiring Harness


The wires, connectors, and switches that carry current and signal between different electrical components on an ebike.


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