Compression Damping

Definition

Compression damping controls how quickly and easily a suspension fork or rear shock compresses under load. It works by restricting the flow of oil through internal valving as the suspension moves inward, dissipating energy as heat rather than allowing it to transfer directly to the rider.

How It Works

Inside a suspension unit, oil is forced through a compression circuit — a series of ports, shims, and valves — as the suspension compresses. The more restricted this flow, the more resistance the suspension offers to compression. This resistance is what we call compression damping.¹

Compression damping is distinct from spring rate. The spring determines how much force is needed to compress the suspension a given distance; the damper controls how quickly that compression happens.

High-Speed vs Low-Speed Compression

Modern trail and enduro suspension separates compression into two circuits based on the speed of shaft movement — not the speed of the bike:

Low-Speed Compression (LSC) Controls damping during slow shaft movements — pedaling forces, rider body movement, pumping, and gradual terrain changes. Increasing LSC firms up the suspension for climbing and reduces pedal bob without significantly affecting response to sharp impacts.

High-Speed Compression (HSC) Controls damping during fast shaft movements — sharp rock strikes, drops, and high-speed impacts. Increasing HSC prevents the suspension from blowing through its travel on large hits. Too much HSC causes harshness on rough terrain.²

Many entry-level forks have a single compression adjustment or only a lockout. Mid-range and above typically offer separate LSC and HSC circuits.

Lockout

A lockout is an extreme form of compression damping — it closes the compression circuit almost entirely to prevent the suspension from moving. Useful for climbing on smooth terrain or road riding, but should be disengaged before hitting rough trail.³

Platform Damping

Platform damping (also called ProPedal or Threshold) adds a small amount of LSC to resist pedal-induced bob without fully locking out. It allows the suspension to respond to impacts while resisting rhythmic pedaling forces.

How to Adjust

Start with both compression dials fully open. Add LSC first — increase it until pedal bob on climbs is manageable, then back off one or two clicks to maintain sensitivity. Adjust HSC based on feel over large hits: if the suspension blows through travel, add HSC; if it feels harsh on sharp rocks, reduce it.

Always set sag before adjusting compression damping.

See Also

• Rebound
• High Speed Compression
• Low Speed Compression
• Lockout
• Sag

References