Anti-Squat

Summary

Anti-squat describes how a bicycle’s rear suspension responds to acceleration. It compares the suspension-extending influence of drivetrain and tire forces with the compression caused by rearward load transfer. Anti-squat is expressed as a percentage and changes with suspension position, gearing, chainring size, wheel size, idler location, and the assumed rider center of mass. Higher values generally make a bike remain higher in its travel under power, while lower values allow more squat. It is an important design measurement, but it does not independently determine pedaling efficiency, traction, or ride quality.

Quick Facts

Category: Suspension kinematics
Applies to: Full-suspension bicycles
Measured as: Percentage
Defined by: Frame geometry, drivetrain layout, gearing, and mass assumptions
Changes through: Suspension travel and gear selection
Related concepts: Instant center, chain growth, pedal kickback

Overview

When a bicycle accelerates, load transfers toward the rear wheel and tends to compress the rear suspension. Chain tension and the driving force at the tire act through the suspension geometry and may oppose that compression.

Anti-squat expresses the calculated balance between those effects. It is best understood as an acceleration-response measurement rather than a complete explanation of pedal bob. Movement caused by the rider’s changing body position, uneven pedal stroke, spring rate, and shock damping is not fully described by anti-squat alone.

Calculations also require assumptions about rider position and center-of-mass height. Two published graphs may show different values for the same frame if they use different gears, geometry settings, or rider assumptions.

How Anti-Squat Works

Interpreting the Percentage

In a simplified model:

100 percent: Drivetrain-induced extension balances acceleration-induced compression.
Above 100 percent: The suspension tends to extend under acceleration.
Below 100 percent: The suspension tends to compress.

These values do not represent efficiency percentages. A bike with 120 percent anti-squat is not 20 percent more efficient than one with 100 percent.

The standard definitions and graphical method are described in this bicycle-suspension patent.

Suspension Position

Anti-squat normally changes as the suspension compresses because the axle, links, and instant center move. Many designs provide substantial anti-squat near sag, where most seated pedaling occurs, and reduce it deeper in the travel.

This can provide chassis support during acceleration while reducing drivetrain influence during larger impacts. It is a common strategy rather than a universal requirement.

Gearing and Chainline

Changing gears alters chain tension, chain angle, and the mechanical relationship between the drivetrain and suspension. Chainring size can also change the anti-squat curve.

The direction and amount of change are design-specific. Anti-squat does not always increase or decrease in the same way across the cassette. A meaningful graph should identify the chainring, rear cog, wheel size, suspension position, and other assumptions used in the calculation.

Instant Center

On a single-pivot bike, the instant center is the main pivot. On multi-link systems, it is a virtual point that moves as the linkage compresses.

The location of the instant center helps determine how driving forces act on the suspended portion of the bicycle. Dual-link and multi-link designs provide more freedom to shape the anti-squat curve, but the number of pivots does not determine whether that curve is good or bad.

Idler Pulleys

High-pivot systems often route the chain over an idler pulley. Its size and position establish a new chain-force path, allowing designers to tune anti-squat and pedal kickback while retaining a rearward axle path.

This is why a rearward axle path does not automatically produce a particular anti-squat value. The drivetrain route must also be considered. Forbidden explains this relationship in its high-pivot suspension overview.

Anti-Squat and Pedal Kickback

Anti-squat and pedal kickback are related but separate measurements.

Pedal kickback results from changes in the effective chain path as the suspension moves. In a conventional drivetrain, some layouts that generate substantial anti-squat also produce chain growth. An idler can change this relationship by redirecting the chain force.

Actual feedback at the pedals also depends on wheel speed, freehub engagement, selected gear, suspension speed, and whether the rider resists crank movement. A theoretical kickback graph does not indicate exactly what every rider will feel.

Rider Experience

A bike with relatively high anti-squat near sag may remain higher in its travel during hard acceleration and feel firm when climbing or sprinting. Excessive anti-squat can create drivetrain feedback or make the suspension more resistant to bump compression while the rider is applying chain force.

A lower value allows more squat during acceleration. This may feel smooth and active but can also make the bike settle into its travel when climbing. Whether that improves traction depends on the shock tune, tires, terrain, rider position, and how steadily power is applied.

Riders are most likely to notice anti-squat during high-torque climbing, standing acceleration, and pedaling across rough ground. It is usually harder to isolate during steady seated riding.

Mechanic’s Perspective

Anti-squat is primarily built into the frame and drivetrain layout. Shock pressure, rebound, compression damping, and volume spacers do not change the theoretical curve. They do change how much movement the rider experiences.

Sag is important because it determines where the bike normally operates on the curve. An undersprung shock may place the suspension deeper in its travel, where the anti-squat value can be different.

If a bike suddenly develops more pedal movement, its kinematics have probably not changed. Inspect:

Shock pressure and damping settings
Shock service condition
Pivot bearings and hardware
Suspension sag
Chainring and drivetrain configuration
Climb-switch operation, where fitted

On idler-equipped bikes, confirm correct chain routing and inspect the idler teeth and bearings. Wear or drag at the idler can affect drivetrain feel even though the calculated anti-squat remains unchanged.

Changing chainring size may alter anti-squat slightly, but chain clearance, gearing, and manufacturer compatibility should take priority over using chainrings as a suspension-tuning method.

Common Design Approaches

Layout	Anti-squat control
Single pivot	Primarily determined by main-pivot position and drivetrain geometry
Dual short-link	Moving instant center allows the curve to change through the travel
Translating pivot	Pivot movement can maintain and then reduce anti-squat in selected travel zones
High pivot with idler	Idler position helps tune anti-squat separately from axle path

DW-Link, VPP, Maestro, and Switch Infinity can all be configured differently from one frame to another. The platform name alone does not indicate a specific anti-squat value. Yeti’s Switch Infinity documentation shows one example of a deliberately changing curve.

Engineering Trade-Offs

Higher anti-squat can provide acceleration support but may increase drivetrain influence and feedback. Lower anti-squat permits more suspension movement but can allow the bike to sit deeper under power.

Designers therefore tune the entire curve rather than targeting one number. Leverage ratio, axle path, shock tune, geometry, intended gearing, and rider position must be considered together.

Buying Considerations

Anti-squat graphs are useful when comparing similar bikes, provided the calculations use comparable inputs. Look at the value near sag and in the gears normally used for climbing rather than focusing on the highest number shown.

Suspension layout, shock tune, geometry, tires, and fit often have a greater effect on the complete riding experience than a small difference in anti-squat.

Common Questions

Does 100 percent anti-squat eliminate pedal bob?

No. It balances specific calculated forces. Rider movement, pedaling cadence, spring rate, and damping can still move the suspension.

Is higher anti-squat more efficient?

Not automatically. It may reduce suspension movement during acceleration, but excessive values can increase drivetrain feedback or interfere with bump response.

Can shock adjustments change anti-squat?

No. They change the suspension’s dynamic response, not its geometric anti-squat curve. Changing sag can move the bike to a different operating point on that curve.

Does anti-squat change between gears?

Yes. Gear selection changes chain force and chain angle, although the direction and size of the change depend on the suspension and drivetrain layout.