Read our definitive techno-pedia
Got into mountain biking and now lost in a world of jargon and acronyms? Help is at hand with our definitive techno-pedia.
Active Braking Pivot — Trek’s suspension design that places the seat stay pivot concentric with the rear axle. ABP helps prevent the rear brake impeding the suspension action.
Dia Compe’s threadless steerer/headset system that is now commonplace on all bicycles.
Short for the air canister on an air sprung rear shock.
Geometric configuration of the suspension to control squatting under acceleration.
Axle to crown height
The true height of a fork, measured from the dropout centre to the top of the fork crown.
Oversized bottom bracket and crank standard.
Bolt circle diameter of the chain rings. The most common sizes on mountain bikes being 104/64mm for 4 bolt and 110/74mm for five bolt spiders.
Pedalling induced suspension compression.
Full compression of the suspension. Often accompanied by a metal on metal knock. Bottoming regularly usually means that the spring rate is too low.
Specialized’s inertia valve suspension technology.
Negative effect of braking on the rear suspension. Stiffening of the rear suspension under braking, dramatically reducing its ability to absorb bumps
Plain bearing or sleeve of material for rotary applications. Found in shock eyelets, suspension links and telescopic forks.
Having variable thickness — usually in reference to frame tubing or spokes.
A self-contained bearing assembly with inner and outer races, ball bearings and seals.
Rear cog assembly, which slides onto the freehub body.
Phenomenon in dampers when a pressure differential causes the damping fluid to temporally vaporise, leading to inconsistent damping.
Shimano’s splined disc rotor/hub interface.
Any system for keeping the chain in place.
Misleading term for SPD type pedals i.e. without toe clips. However, flat pedals are also clipless.
Damping created when the wheel hits a bump and compresses the suspension. High-speed compressions are square edge hits like roots and rocks, low-speed compressions are generated by rolling terrain or rider inputs from body movements and pedalling.
The dissipation of energy from a dynamic system, usually in the form of a hydraulic damper.
An adjuster click.
Compression of the front suspension under braking. Increasing the sping rate or low-speed compression damping helps combat diving.
Department of transport rated brake fluid. Usually Dot 4 or 5.1 for mountain bike brakes.
The right-hand side of the bike i.e. with the drivetrain.
Any fork with two crowns. Often called triple clamps, because each stanchion is camped at two points and the lower leg also clamps the hub axle.
A measure of the hardness, usually in reference to tyre rubber.
Dave Weagle’s twin link suspension design.
When oil and gas mix in a damper (shock), causing inconsistent damping.
The force required to compress the suspension decreases as you move through the travel.
Any four bar suspension design with a fixed main pivot.
Fox Isolated Technology. Closed damper design that eliminates aeration of the damping fluid.
Terminology for the amount by which the front axle is offset from the steering axis.
The geometric name given to all of the tapered head tube standards.
Future Shock Rear: Specialized’s four-bar rear suspension design.
Any bike with suspension front and rear. Short for full suspension or fully suspended.
The geometric parameters of a bicycle that determine its handling.
Sram’s lightweight twist grip shifters.
Sram’s two-speed planetary-geared crankset.
Any bike with front suspension and a rigid frame.
The part of the frame that carries the headset bearings and front fork.
Shimano’s two-piece hollow crank design and external bottom bracket standard.
The chain stay pivot on a four bar suspension design. Named after its inventor, Horst Leitner.
A process were high pressure fluid is used to form complex tubing profiles.
Instantaneous centre of rotation. Basically, a virtual pivot.
Opposite to conventional forks, so you have the stanchions below the upper tubes. Also called upside-down forks.
International Standard Chain Guide mount: A standardised configuration for the three bottom bracket tabs and corresponding holes in a chain device..
Inter Spoke Milling. A process introduced by Mavic for removing excess rim material between spoke holes.
J-shaped axle path
Any axle path that is initially rearward than goes vertical.
Lightweight, folding alternative to a tyre’s wire bead.
The amount of offset a seatpost head has.
Direct relationship between wheel and shock travel. So a 6in travel bike with a 2in stroke shock has a 3:1 leverage ratio. It is the mechanical advantage of the rear wheel on the shock. It’s typically 3:1 on a trail bikes but some designs with long stoke shocks can be as low as 2:1.
The force required to compress the suspension is constant.
A series of mechanical levers designed to change the leverage on the shock as the suspension compresses.
Any mechanism to switch the suspension off, by locking it in the fully extended position.
Also called fork lowers or lower casting.
Giant Bicycles’ twin-link suspension design.
Bolt-through quick release system from RockShox.
Micro Cellular Urethane bumpers also know as elastomer springs.
Interchangeable with derailleur, so you have a rear mech.
Disc brakes with cable, rather than hydraulic actuation.
Synthetic fluid used in Shimano hydraulic disc brakes.
One-piece construction commonly used in aerospace engineering.
Brass or alloy nut used to tension a spoke.
The left-hand side of the bike, without the drivetrain.
Open bath dampers use the same oil for damping and lubrication, while closed cartridge units have separate damping and lubrication fluids.
Spring-loaded teeth that engage the ratchet ring in a freehub.
Radial disc brake caliper mount, first introduced by Manitou.
Pre-compression of a spring, that increases the amount of force required to activate the suspension. Used to adjust the static ride height (sag) of the suspension.
Works in the opposite direction to more commonplace push shocks. So any rear shock where spring resistance and compression damping increase on the pull phase of the stroke.
A measure of crankset width, taken between the outer most points of the pedal inserts.
Quick Release — Any lever using a cam mechanism for applying a clamping force.
Suspension movement in extension.
Hydraulic damping created on the rebound stroke as the suspension extends. Too much rebound damping causes the suspension to get stuck down, too little will have you bouncing up and down like a pogo stick.
The force required to compress the suspension increases as you move through the travel.
The amount by which the suspension compresses under the static weight of the rider and bike. Set by changing the spring rate and adjusting spring preload. Sag varies depending on the application, less for cross-county more for downhill, but it is typically 25-30% of the total travel on a trail bike.
Any bearing system with a seal to prevent dirt or water ingress. So, a cup and cone set-up can still be referred to as sealed bearings.
A fork with one crown, giving a fixed axle-to-crown height.
Any rear suspension design where the axle path is determined by a fixed pivot.
Shimano Indexing System.
Shimano Pedaling Dynamics. Shimano’s revolutionary clipless pedal design.
Bicycle with only one gear.
Dave Weagle’s single pivot suspension design with a concentric rear axle pivot. Same concept as Trek’s ABP.
Any mechanical device that stores energy as it is displaced. Normally air or coil, where air springs are lighter and coil springs are more sensitive.
The amount of weight required to compress a spring by a given amount. So a 300lb/in coil spring requires 300lb to compress it by one inch and 600lb to compress it by two inches. Metric units are kg/mm. The lower the spring rate the ‘softer’ the spring is. Air spring rates are measured in PSI or bar. Heavier riders need higher spring rates.
Everything on the bicycles that is suspended or isolated from bump forces. Includes the rider, frame and most of the components.
Rear suspension compression under acceleration.
Upper tubes on a conventional telescopic suspension fork.
Shimano Total Integration.
From static friction. Initial resistance in a suspension system created by seals, bushings, bearings or lack of lubrication. Less is better. Lots can seriously degrade small bump sensitivity.
The connecting structure between the main pivot (or pivots) and the rear axle.
Full extension of the suspension. Often accompanied by a metal-on-metal knock if there is insufficient rebound damping or no bump stops.
The amount of suspension movement given in inches or millimetres. XC bikes typically have 80-100mm, Trail bikes have anything from 120 to 160mm while downhill bikes can have up to 250mm.
Everything on the bicycle that isn’t suspended. Wheels, rotors, fork lowers, the swingarm and a portion of the rear shock make up the unsprung mass. Basically, everything that has to ride up and over the bumps.
Mavic’s Universal System Tubeless.
Cantilever rim brake.
The force required to compress the suspension varies as you move through the travel.
Any suspension design without a fixed pivot. FSR, DW-link, VPP, VPS, Maestro, Zero all have virtual pivots or instant centres.
Virtual Pivot Point. Patent protected virtual pivot suspension design with counter-rotating links.
Gravitational force action on a given mass.
Horizontal distance between the front and rear wheel axles.
The 12x142mm rear hub and dropout standard from Syntace.
Shimano’s ultra high-end aftermarket upgrade kit for previous XTR.
Zero Suspension System
Mondraker’s twin-link rear suspension design with floating shock.