One of the most crucial components of any mountain bike is the rear suspension. It absorbs shocks, smooths out the ride, and makes the bike more capable of handling rough, technical terrain. The design of rear suspension systems can vary greatly between different bikes and brands, each bringing unique benefits and limitations to the table. Whether you’re new to mountain biking or looking to upgrade your current setup, understanding how different suspension designs work is key to making an informed choice.

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What Does Rear Suspension Do?

At its core, the primary function of rear suspension is to absorb the impacts and forces generated when the rear wheel hits obstacles such as rocks, roots, or drops. This impact absorption is important to maintaining control, comfort, and speed on rough terrain. However, suspension systems must also accommodate the rider’s movements — from pedaling to braking — while navigating these obstacles.

Key Factors Affecting Suspension Performance

Several factors come into play when designing rear suspension, including:

1. Axle Path: This refers to the line the rear axle traces during suspension compression and extension. The path can be forward, vertical, rearward, or S-shaped. The axle path directly influences how the bike handles impacts, climbs, and descents.
2. Pivot Locations: The position of the bike’s pivot points determines the axle path. These pivot points affect how the suspension performs during compression and how the rider’s pedaling forces influence the bike.
3. Leverage Ratio/Curve: The leverage ratio is the ratio between how much the rear axle moves and how much the shock compresses. This ratio can vary through the suspension’s travel and plays a role in determining the bike’s progression (how much force is needed to compress the shock). A higher leverage ratio provides more sensitivity, while a lower one increases progression to prevent bottoming out.
4. Shock Absorber and Spring: The shock absorbs impact forces and, with the spring, returns the bike to its uncompressed position after an impact. The shock also typically includes damping features to control how fast the shock compresses and rebounds.

Common Rear Suspension Designs

Now that we understand what rear suspension systems do, let’s explore the most popular suspension designs used in modern mountain bikes, as well as their pros and cons.

1. Single Pivot Suspension

The single pivot is the simplest and one of the most commonly used suspension designs. It features a single pivot point where the rear axle connects to the swingarm. The shock is typically connected directly to the swingarm, which moves in a consistent arc during compression.

Pros:

• Simple and effective design
• Requires fewer bearings, making maintenance easier
• Suspension action is predictable throughout its travel

Cons:

• Little control over the leverage curve, resulting in a more linear suspension feel
• Limited progression, making it harder to avoid bottoming out, especially with coil shocks

2. Linkage-Driven Single Pivot (Faux-Bar)

The linkage-driven single pivot is similar to the single pivot design but incorporates a linkage that drives the shock. This allows the frame designers to manipulate the leverage curve, making the suspension more progressive and customizable.

Pros:

• Improved leverage curve tunability
• Allows for better suspension performance, particularly on steeper or more technical terrain

Cons:

• More maintenance than a single pivot design
• Limited tuning options due to a fixed instant center

3. Trek ABP and DW Split-Pivot Systems

The Trek ABP and DW Split-Pivot systems feature a unique concentric dropout pivot at the rear axle, which separates the braking forces from the pedaling forces. This system allows the bike to perform like a linkage-driven single pivot in terms of pedaling, but like a Horst-link in terms of braking, providing more consistent braking power.

Pros:

• Reduced anti-rise (the tendency for the rear suspension to stiffen when braking)
• Better pedaling performance while maintaining good braking efficiency

Cons:

• More maintenance compared to simpler suspension designs
• Slightly heavier due to additional components

4. High Pivot Suspension

High-pivot bikes place the pivot point much higher on the frame, often using an idler pulley to route the chain past the pivot. This design creates a rearward axle path, which helps the bike handle square-edge impacts more effectively. The idler pulley also minimizes pedal kickback, which enhances suspension sensitivity.

Pros:

• Rearward axle path improves momentum over rough terrain
• Very low levels of pedal kickback, improving overall suspension performance

Cons:

• Increased maintenance due to the idler pulley
• Potential for drivetrain drag and added weight
• Some designs may lead to increased anti-rise, making the bike stiffer under braking
• Longer chains may be necessary, adding cost and weight

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Choosing the Right Suspension for You

When selecting a mountain bike, consider your riding style and the type of terrain you’ll be riding on most often. If you’re a seasoned rider who loves tackling technical descents, a high-pivot design or a linkage-driven single pivot may be the best option for you. However, if you prefer a more straightforward, low-maintenance ride with smooth pedaling efficiency, a single-pivot system might be all you need.

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