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Core terms and principles used to understand bicycle geometry, suspension behavior, setup, performance, and service.
Technical entry
Axle-to-Crown
Axle-to-crown is a fork-length measurement taken between the center of the front axle and the crown-race seat at the […]
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Effective Top Tube
Effective top tube (ETT) is the horizontal distance between a specified point on the head tube and the seat-tube […]
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MTB Geometry
MTB geometry is the collection of frame, fork, and wheel dimensions that determines how a mountain bike fits, steers, […]
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Instant Center
The instant center is the point about which a suspension member is momentarily rotating at a specific position in […]
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Front-Center
Front-center describes the distance from the center of a bicycle’s bottom bracket to the front-wheel axle. It is a […]
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Suspension Sag Adjustment
Suspension sag is the amount a bicycle’s fork or rear shock compresses under the rider’s weight in a normal […]
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BCD (Bolt Circle Diameter)
BCD, or Bolt Circle Diameter, describes the diameter of the circle passing through the centers of a chainring’s mounting […]
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3x Drivetrains
A 3× drivetrain uses three front chainrings with a multi-sprocket cassette or freewheel. It can provide very low climbing […]
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Stack
Stack is the vertical distance from the center of a bicycle’s bottom bracket to the top-center of the head […]
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Reach
Reach is the horizontal distance from the center of a bicycle’s bottom bracket to the center of the top […]
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1x Drivetrains
A 1× drivetrain uses one front chainring and a multi-sprocket rear cassette. Eliminating the front derailleur simplifies shifting and […]
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Leverage Ratio
Leverage ratio describes the relationship between rear-wheel movement and shock compression on a full-suspension bicycle. It is normally expressed […]
Read entryTopics intentionally overlap. A drivetrain component can also be a technology; an e-bike system can include components, software, and manufacturing concepts. Cross-listing keeps related reference material discoverable from more than one path.
Technical entries are one part of bicycle knowledge for the life of the bike. Discover bicycles in the Archive, use the Encyclopedia to understand them, then carry useful context into Bike Reports or My Garage.