Leverage Ratio

Summary

Leverage ratio describes the mechanical relationship between rear wheel movement and rear shock compression in a full-suspension mountain bike. It reflects how much force and motion are transferred through the suspension system, shaping how the bike feels over bumps, how it responds to rider input, and how effectively the rear shock manages impacts. This ratio is at the heart of suspension performance — influencing sensitivity, progression, spring rate selection, and bottom-out resistance across all travel ranges.

Key Facts

  • Category: Concept
  • Also Known As: Suspension leverage ratio
  • Measured As: Rear wheel travel ÷ shock stroke
  • Common Range: 2.0:1 to 3.5:1
  • Used on: All full-suspension mountain bikes
  • Directly Influences: Suspension feel, spring rate, damping, progression, bottom-out behavior

Overview

In the design and tuning of full-suspension bikes, leverage ratio is one of the most important — yet often misunderstood — metrics. It defines how much rear wheel travel occurs relative to the stroke length of the rear shock. Put simply, a leverage ratio of 3:1 means the rear axle moves 3 millimeters for every 1 millimeter of shock compression.

This number isn’t just theoretical. It has real-world consequences for how your bike rides. A higher leverage ratio amplifies both wheel motion and input force at the shock, affecting how easily the suspension activates, how it ramps up, and how much spring and damping support the system requires. Lower leverage ratios, by contrast, reduce the shock’s workload but may trade off small-bump suppleness.

More importantly, leverage ratio is not fixed across the travel. Most suspension platforms are designed with a leverage ratio curve that evolves through the stroke — creating progression, support, or ramp-up characteristics tailored to a specific ride style or terrain.

Whether you’re a rider looking to better tune your shock, or a designer shaping how a bike behaves through rough terrain, leverage ratio is central to the conversation.

How It Works

1. Basic Calculation

The leverage ratio is defined as:

Leverage Ratio = Rear Wheel Travel ÷ Shock Stroke

Example:

  • 150 mm of travel
  • 50 mm shock stroke
  • 150 ÷ 50 = 3.0:1 leverage ratio

This means the suspension multiplies movement at the wheel by three as it acts on the shock.

2. Average vs. Instantaneous Leverage

  • Average leverage ratio is a single number summarizing the entire travel range — useful for broad comparisons.
  • Instantaneous leverage ratio is the actual value at any point in the travel — which is what really matters in tuning and feel.

A bike’s leverage ratio curve maps these instantaneous values from start to finish and defines how the suspension behaves over bumps, hits, and body movement.

3. Common Leverage Curve Types

  • Linear: Constant leverage ratio — rare in modern designs
  • Progressive: Ratio decreases as the bike goes deeper into its travel → more bottom-out resistance
  • Regressive: Ratio increases through the stroke → generally avoided, except for specific cases
  • Mixed or Digressive–Progressive: High initial leverage for small bump sensitivity, transitioning into mid-stroke support and strong ramp-up

These curves are designed by frame engineers through pivot placement, linkage configuration, and shock orientation.

Why It Matters

A. Suspension Feel

  • Higher leverage ratios (e.g. 3.2:1–3.5:1):
    • More movement per mm of shock stroke
    • Suppler early travel
    • Faster shock response
    • But may overwhelm small shocks, increase heat buildup, and reduce bottom-out control
  • Lower leverage ratios (e.g. 2.0:1–2.4:1):
    • More support
    • Better suited for heavier riders or hard impacts
    • Allows lower spring pressures and finer damping adjustment
    • May feel firmer over small chatter unless paired with sensitive shocks

B. Spring Rate and Shock Tuning

Leverage ratio directly determines:

  • Air pressure required in air shocks
  • Coil spring stiffness for coil shocks
  • Rebound and compression damping range
  • Ramp-up volume spacing and bottom-out support

This is why bikes with the same rear travel may feel totally different — leverage curves dictate how aggressively that travel is used.

C. Shock Compatibility and Wear

High leverage bikes (3.2+:1) often require larger volume shocks with better heat management, while lower leverage platforms may use more compact or lighter shocks. Over time, high leverage can increase stress and wear on suspension components if not properly tuned.

Performance Considerations

A well-designed leverage ratio offers a balance between sensitivity, support, and durability. Different ride styles and bike categories target different ratios:

  • Trail / All-Mountain: Balanced around 2.5:1 to 2.8:1 for versatility
  • Enduro / Downhill: Often lower average ratios (2.3:1–2.6:1) for heavy hits
  • XC / Race Bikes: Sometimes higher leverage (2.8:1–3.2:1) to save weight and offer quick response
  • E-Bikes: Typically lower ratios to manage increased rider and system weight

Designers aim to match leverage with shock stroke, frame stiffness, intended use, and rider input to craft a system that feels fast, controlled, and efficient.

Notable Examples

  • Santa Cruz V10: Uses a low, consistent leverage ratio to give downhill racers precise tuning and better damping control
  • Specialized Enduro: Features a progressive curve with early suppleness and strong ramp-up for big terrain
  • Yeti SB150: Combines Switch Infinity with a leverage curve that delivers both climbing traction and downhill plushness
  • Transition Spire: Designed for aggressive riders, with a rising-rate curve that maintains control through heavy compressions
  • Trek Slash: Uses a balanced leverage profile optimized for full-stroke use with modern air shocks

Related Terms

See Also on BBB

References

  • Fox Racing Shox Suspension Setup Guides
  • RockShox Tuning Manuals
  • Pinkbike Tech: “How Leverage Ratios Shape Ride Feel”
  • BikeRumor: Suspension Curves Explained
  • Linkage Design Software Reports (Professional Use)
  • Manufacturer White Papers (Santa Cruz, Trek, Ibis)
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