The Bicycle Repair Glossary, B
B-Tension Screw | Ball bearing | Banana seat | Bar ends | Bar plugs | Barrel adjuster | Bead | Bead Seat Diameter (BSD) | Bearing | Bidon | Billet | Binder bolt | Biopace | Bicycle Motocross (BMX) | Bolt | Bolt Circle Diameter (BCD) | Boot | Bottom bracket | Bottom pull | Brake | Brake bridge | Brake lever | Brass | Braze-on | Breaker bar | Brifter | Bull horn handlebar | Bungee cord | Bushing | Butted
B-Tension Screw - The screw that regulates the tension of the rear derailleur's upper pivot spring.
Ball bearing - A type of bearing where the connection is made by balls that roll between the two parts.
Banana seat - A very long seat on some old-fashioned bicycles that connected at the seatpost and to supports on the rear axle.
Bar ends - Extensions that fit on the end of a mountain bike handlebar. Provide another hand position that offers greater leverage.
Bar plugs - Not to be confused with bar ends, these fit inside the ends of a handlebar to increase safety and protect the fragile end of the handlebar.
Barrel adjuster - A hollow, threaded bolt that functions as a cable housing stop. Allows for fine shifter cable adjustments, and works great to take up cable slack as brake pads wear down.
Bead - A circular length of steel cable or kevlar that forms one edge of a tire.
Bead Seat Diameter (BSD) - The diameter of a wheel, specifically at the point where the tire bead sits.
Bearing - A point of contact between a turning and non-turning part.
Bidon - The French term for "water bottle." I've also heard it used in Australia.
Billet - A solid piece of metal that is cut down to make parts.
Binder bolt - A bolt that binds two sides together when tightened, such as the seat post binder bolt. (Also see, pinch bolt.)
Biopace - A line of oblong chainrings produced by Shimano in the 1980's.
Bicycle Motocross (BMX) - A type of racing where riders race 20" singlespeed bicycles around a dirt track consisting of jumps and berms. Races usually last around 60 seconds.
Bolt - A fastener with male threads.
Bolt Circle Diameter (BCD) - The diameter of the circle formed by the stack bolts on a crankset. The way you match crankset to chainrings.
Boot - A temporary patch used to cover a hole in the tire, to prevent the tube from popping out.
Or, an accordian-like piece of rubber used to seal sliding parts. Found on suspension forks and V-brakes.
Bottom bracket - The component that fits in a frame's bottom bracket shell. Consists of a spindle and bearings, around which the crank arms rotate.
Bottom pull - A style of front derailleur operated by a cable coming up from below to pull from the bottom of the derailleur. Also see "top pull."
Brake - A device to stop the bicycle.
Brake bridge - The short length of tubing connecting the seatstays just above the rear tire. Provides a mounting location for rear brake.
Brake lever - A lever, usually located on the handlebar, that operates the brake.
Brass - An alloy of copper and zinc. Commonly used for spoke nipples.
Braze-on - A small fitting permanently attached to the frame, typically for the front derailleur to mount to, as well as cable stops and guides.
Breaker bar - A long bar with a socket attachment at one end. Provides more leverage than a typical ratchet and socket; great for freeing stuck fastners.
Brifter - The combination of both brake and shift levers into one unit. Usually found in Shimano, SRAM, and Campy road components.
Bull horn handlebar - A style of handlebar that is flat across the center but has upturned ends, like the horns of a bull. Typically used as the base of aero bars.
Bushing - A hollow cylindrical part that connects two other parts when bearings aren't needed. Typically found in the rear derailleur pulleys.
Butted - Frame tubing (as well as spokes) that is thicker at the ends than in the middle. Maintains strength yet saves weight.