MTB Suspensions Jargon for Beginners

Mountain bike suspension terminology gets confusing quickly, especially when rebuilding shocks, servicing forks, or discussing tuning and damping systems.

This guide breaks down common MTB suspension terms in a simpler and more beginner-friendly way while still keeping the technical language riders and suspension techs actually use.

Damper vs Spring

Every shock or fork has two main systems:

  • Spring: Stores energy from impacts and rider input.
  • Damper: Controls how quickly the suspension compresses and rebounds.

The damper controls both compression damping and rebound damping.

Without damping, the suspension would compress and rebound far too quickly, causing uncontrolled bouncing and poor traction.

Rear Shock Terminology
  • Damper Tube:
    Cylinder where the main piston moves.
  • Inner Damper Tube:
    Secondary tube found in twin-tube shocks.
  • Damper Body:
    Main housing containing the piggyback and damping systems.
  • Damper Shaft:
    Shaft connecting the eyelet to the piston assembly.
  • Main Seal Head:
    Seals and guides the shaft.
  • Adjusters:
    Controls used to adjust rebound and compression damping.
  • Eyelets:
    Shock mounting points using standard hardware.
  • Trunnion Mount:
    M10 bolts threading directly into the shock body.
  • Piggyback Reservoir:
    Additional oil volume and pressure compensation system.
  • IFP:
    Internal Floating Piston separating oil and air.
  • Bladder:
    Flexible alternative to an IFP.
  • Base Valve:
    Compression damping circuit.
  • Mid Valve:
    Piston assembly controlling oil flow during compression and rebound.
  • Hydraulic Bottom-Out (HBO):
    Hydraulic system slowing the end of travel.
Air Shock Terminology
  • Air Piston:
    Compresses air to generate spring force.
  • Inner Air Can:
    Cylinder where the air piston moves.
  • Negative Chamber Seal Head:
    Seals the negative chamber.
  • Outer Air Sleeve:
    Outer housing containing seals and spacers.
  • Volume Spacers:
    Increase end-stroke progression.
  • Eyelets:
    Structural mounting ends of the shock.

Coil shocks use preload threads while air shocks rely on airtight seals and polished surfaces.

IFP & Reservoir Systems
  • Schrader Valve:
    Older reservoir filling method.
  • IFP Fill Adapter:
    Modern high-pressure fill system.
  • Needle Fill:
    Compact high-pressure filling system.
Fork Suspension Terminology
  • Left Stanchion:
    Usually contains the spring system.
  • Right Stanchion:
    Usually contains the damper.
  • Lower Legs:
    Outer magnesium fork casting.
  • Foot Nuts / Bolts:
    Retain shafts inside the lowers.
  • Damper Shaft:
    Internal shaft driving damping.
  • Air Shaft:
    Defines travel and spring curve.
  • Seal Head:
    Separates damper oil from lower oil.
  • Rebound Assembly:
    Contains rebound adjustment systems.
  • Base Valve:
    Main compression damping circuit.
What Are Shims?

Shims are thin steel washers that flex to control oil flow.

They are one of the core components controlling suspension damping behavior.

Different shim stacks dramatically change suspension feel and tuning.

Suspension Service Tips & Warnings
  • Always grease seals during reassembly.
  • Confirm mounting type before ordering hardware.
  • Use the correct pressurization tool.
  • Fully depressurize air systems before opening.
  • Some IFP systems exceed 350 psi.
  • Always clamp shafts correctly.