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The Bicycle Repair Glossary, 1-A


105 | 20 inch | 26 inch | 27 inch | 29er, 29 inch | 3rd Hand Tool | 4130 | 4th Hand Tool | 650b | 700c

Acorn nut | Adjustable cup | Aerodynamic | Aero bars | Aftermarket | Aheadset | Alignment | Alivio | Altus | Allen wrench | Alloy | Aluminum | Anatomic | Anchor bolt | Anti-rotation washer | Anodized | Axle


105 - A line of Shimano road components. A road group. A step above Tiagra, a step below Ultegra.

20 inch - Refers to bikes with 20" wheels, typically BMX bikes or children's bikes.

26 inch - Refers to bikes with 26" wheels, the standard size wheel for mountain bikes.

27 inch - Refers to bikes with 27" wheels, which were most old-school "10 speed" road bikes.

29er, 29 inch - Refers to bikes with 29" wheels, pronounced as "two niner." Newly popular mountain bike wheel size.

3rd Hand Tool - A tool used to clamp brake pads onto the rim and hold them in place. This frees both hands for you to adjust the brakes.

4130 - The numerical designation for chrome-moly steel. Typical metal for high quality BMX bikes.

4th Hand Tool - Another tool for brake adjustments. This pulls the cable taut, freeing your hands to tighten the anchor bolt with ease.

650b - Another mountain bike wheel size that is half way between typical 26" wheels and the newer 29" wheels. Uncommon.

700c - The typical size for a road bike wheel. Also happens to be the same size as a 29" wheel.


Acorn nut - A closed-end style of nut that resembles an acorn. Easier to turn by hand.

Adjustable cup - Typically paired opposite a "fixed cup" in a conventional bottom bracket. The adjustable cup can be adjusted and then secured with a lockring to hold the proper adjustment setting.

Aerodynamic - Describes bicycle parts or riding positions that reduce wind resistance.

Aero bars - Handlebars or clip-on handlebar attachments that allow a rider to ride in a lower, more aerodynamic position. The bars have hand holds, but support a rider's forearms. Usually seen on Time Trial (TT) and Triathlon bikes. Not allowed in road bike races.

Aftermarket - Components that were not part of the original bicycle. Usually refers to upgraded parts and any accessories.

Aheadset - The original threadless headset. "Aheadset" is a trademarked term of Dia Compe.

Alignment - Refers to frame and fork. When everything is centered and equally spaced.

Alivio - A line of Shimano mountain bike components.

Altus - A line of Shimano mountain bike components.

Allen wrench - Also known as a hex wrench.

Alloy - Any metal that is a blend of more than one metal.

Aluminum - A lightweight metal that does not rust. Very popular for bicycle frames and components.

Anatomic - Any component that is designed to be a better fit to the cyclist's body. Usually refers to parts you touch, such as handlebars and brake levers.

Anchor bolt - A bolt that clamps down on a brake or derailleur cable to hold it in place.

Anti-rotation washer - A washer with a tab on one side that fits into a slot, preventing the washer from turning or rotating.

Anodized - When an aluminum frame or component is electroplated rather than painted. Anodization is lighter and more durable than painting.

Axle - The shaft running through the hub of a wheel.



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