Motorcycle Suspension Systems Explained: Ultimate Guide

The motorcycle industry is constantly evolving, bringing exciting new features to the bikes we know and love.

However, with these new advancements come challenges for those who work on two-wheelers, whether it be as a hobby or for those who are full-time motorcycle technicians.

Today’s bikes are more complex than ever, and understanding how the suspension of your motorcycle works may seem like an intimidating task at first. However, learning how it’s set up, how it affects your riding and how to make adjustments is a great first step to fully understanding your bike and how to keep it in optimal condition.

Keep reading to learn all about motorcycle suspension systems and how this knowledge can apply to a career in the industry.

Key Summary Points

• Motorcycle suspension basics: The primary function of suspension systems for motorcycles is to maintain tire contact with the ground, absorbing impacts from road imperfections to ensure a smooth ride and prevent loss of control. Suspension systems vary between on-road and off-road motorcycles, with adjustability features like ride height and spring tension to accommodate different rider weights and riding styles.
• Components of suspension systems: The most common motorbike suspension setup includes a coil spring paired with a hydraulic damper. Springs allow for wheel movement independent of the chassis, while dampers control the springs’ motion. This article explains the difference between linear and progressive springs, as well as the role of dampers in managing spring action through hydraulic fluid.
• Adjustability features: Advanced motorcycle suspensions offer adjustability options such as preload, which is the tension on the springs when the bike is at rest. Adjusting preload can help adapt the bike for solo riding, carrying a passenger or adding luggage. This article also discusses sag, which is the suspension's compression under the bike's weight, and how it affects ride quality.
• Front- and rear-suspension details: Motorcycles typically use suspension forks at the front, with some systems integrating both springs and dampers in each fork leg, while others separate these components. The rear suspension often features a heavy-duty coil around a damper, with adjustments for preload and damping to support the greater weight at the back of the bike.
• Career opportunities for technicians: Understanding and tuning motorcycle suspensions is a crucial skill for technicians, with potential specialization in suspension tuning as a standalone business. This article highlights common tasks for suspension technicians, including changing springs, replacing fork fluid and seals, and making adjustments for optimal rider setup. It also covers Motorcycle Mechanic Institute’s training program as a pathway to a potential career in the motorcycle industry.^1.1

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Motorcycle Suspension Explained

The primary goal of a motorcycle’s suspension system is to keep the vehicle’s tires in contact with the ground. Without proper suspension, tires would lose traction when encountering bumps, dips or other ground imperfections. We can’t forget about braking, acceleration or cornering forces, either.

Without suspension, any impact between a vehicle tire and a ground imperfection is at best uncomfortable, and at worst, the cause of a dangerous crash.

How suspension works

Motorcycle suspensions use a spring and damper combination to isolate the chassis and rider from road imperfections. On-road motorbike suspension systems work to minimize the effect of potholes, bumps, cornering and acceleration/deceleration forces. Off-road motorcycle suspension systems handle roots, rocks, jumps, ledges and more.

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Basic vs. premium suspension

Basic motorcycle suspension lacks adjustability. It works fairly well in a wide variety of circumstances, whereas premium suspension is tunable to rider weight and intended riding type. Cruisers or dual-sport motorcycles have vastly different needs than a dedicated sport bike.

Adjustability features

Adjustability can include ride height (under load), fine-tuning how quickly springs compress or rebound as well as preloading spring tension to accommodate differing weight for various riding styles, such as riding with a passenger and/or luggage.

Common suspension systems

The most common suspension systems found on motorcycles use a coil spring and hydraulic damper setup. Air springs and other types of suspension exist, which will be covered more in-depth in another article.

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Springs

Motorcycle wheels need springs to move independently from the chassis and damper control, and manage the movement of the spring. A motorcycle riding only on springs would bounce continuously and dangerously after every road impact.

Springs are coiled steel wire that compress or stretch when acted upon by an external force. Spring rate is the measurement of force required to compress it a certain distance, which is typically measured in pounds-per-inch, and varies with material thickness and the number of coils. Heavier-duty springs will have relatively thicker coils spaced further apart from one another.

• Linear-rate springs offer consistent resistance throughout the spring travel. If 10 pounds will compress the spring one inch, 20 pounds would compress it two inches, and so on.
• Progressive springs require more and more force to achieve the same travel. Progressive springs are essentially two (or more) springs in one, with both widely and narrowly spaced coils. Initially, a lighter force will compress the first coils, and then a greater force will compress the remaining coils.

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Dampers (Shock Absorbers)

In its most basic sense, a damper slows and controls spring action. Dampers control spring action using hydraulic fluid, which travels through a series of passages and restrictions.

A piston with a precisely measured passage (orifice) travels within the shock body in a bath of hydraulic fluid. The weight of the fluid and the size of the passage determines the piston’s travel speed. When a motorcycle encounters a bump, dampers slow spring compression and rebound as the fluid slowly travels through the passages within the shock body.

Image Credit: Yamaha

Kinetic energy from spring movement turns into heat energy within the damper, and the hydraulic fluid dissipates the heat. Rear motorcycle shocks generate much more heat than front forks, due to the additional loads they support.

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Compression and Rebound Damping

Compression damping is the intentional slowing of spring compression (hitting a bump) travel. Rebound damping is the intentional slowing of the spring expansion as it resumes to its natural state.

Some motorcycles will have both high- and low-speed adjustments to compression and rebound damping. Sport bikes and off-road motorcycles typically offer greater adjustability than entry-level, or cruiser-style motorcycles.

High- and low-speed damping refers to the speed of the suspension travel, rather than the speed of the motorcycle. High-speed damping affects suspension behavior when hitting a sudden pothole on the street, or an individual rock on a trail. Low-speed damping affects behavior such as braking-related dive or cornering changes. Motorcycle damping is accomplished through:

• Damper rod: Fluid travels through a fixed orifice to control the compression and rebound of the suspension. Damper rods are inexpensive to produce but are limited in their effectiveness. Low-speed damping is too soft and high-speed damping is too harsh.
• Cartridge forks: Fluid travels through a set of stacked shims to control suspension movement. Shims bend and flex as the fluid travels past them. Cartridge forks are more tunable and offer better damping from low to high speed. They are more complicated and more expensive to produce.

In the image below, you can see how the shims bend and flex as oil travels between the upper chamber (A) and the lower chamber (B).

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Sag

Motorcycle springs are always under tension, even when stationary. Vehicle weight causes compression at all times. Add a rider or two and luggage, and the suspension compresses even further.

Sag is the percentage of suspension travel utilized while stationary. If the suspension sags too much when at rest, the bike may bottom out when encountering bumps once underway. Too little sag can cause a stiff, harsh ride.

Preload

Some motorcycles offer suspension preload adjustability. Preload is the amount of tension on the springs when the bike is at rest. Increasing preload will decrease sag, and vice versa. Since a single motorcycle is often used for solo riding, riding with a passenger or riding with luggage, preload adjustment allows a degree of adaptability for multiple use cases.

Although not recommended, adjusting preload can increase ground clearance for off-road travel or decrease seat height for shorter riders. Some novice riders use preload as a ‘band-aid’ for overcoming incorrect spring stiffness relative to their height and weight. While not ideal, this is a common practice, as changing springs is expensive and labor-intensive.

The image below shows a typical motorcycle rear-suspension preload adjuster. By turning the bottom adjuster collar, more or less preload force is applied to the spring, while not changing the overall length of the spring. Increasing preload will result in less suspension sag once under rider load.

Photo Credit: Progressive Suspension

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Motorcycle Front Suspension

Up front, motorcycles use suspension forks. In some systems, both springs and dampers work together within each fork leg. In others, one leg contains the spring and the other contains the damper (separate function forks).

The front-wheel axle mounts to the lower end of the suspension fork, and the triple tree secures the top end.

Motorcycle Rear Suspension

Out back, it is common to see a heavy-duty coil wound around a damper, with external adjustments for preload and damping. Motorcycle rear suspension carries more weight than the front, so heavier-duty springs are common.

On some motorcycles, dual rear shocks are mounted between the frame and the swingarm directly. On others, a linkage and single shock system handle suspension needs.

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How To Adjust Motorbike Suspension Systems

Adjusting your motorcycle's suspension requires a few simple steps—and maybe a little test ride for good measure! Here’s your guide on how to adjust motorbike suspension systems:

Step 1: Gather your tools

Make sure you have all the tools you need at hand. You’ll typically need:

• Measuring tape
• Spanner or socket wrench
• Screwdriver

Step 2: Check the owner’s manual

Grab your owner's manual and find the suspension settings. They often have specific recommendations for your make and model.

Step 3: Set the sag

The sag is how much your bike sinks when you’re on it. To check it, measure from the rear axle to an appropriate point on the bike when it’s unloaded, then measure again when you’re sitting on it. Adjust the preload until you hit that sweet spot—generally around 25 to 30% of the total travel for the rear suspension.

Step 4: Adjust compression and rebound

Next up, the compression and rebound settings control how your bike reacts to bumps. Start with the manufacturer’s recommended settings and then tweak them to your liking! Too much rebound and your bike will feel bouncy, while too little can make it feel sluggish.

Step 5: Test ride

Hop on your bike and take it for a spin. Pay attention to how the suspension feels—does it absorb bumps like a pro, or does it feel like you’re riding a pogo stick? Make adjustments as needed. It might take a few tries to find that perfect balance.

Step 6: Fine-tune

Once you’ve taken your joyride, you might want to adjust your settings again based on your personal preference, riding style and the types of roads you encounter. It’s all about making your ride as comfortable and responsive as possible.

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How Do Motorcycle Suspension Systems Apply to Techs?

Setting up and tuning motorbike suspension systems is a common technician task. In fact, suspension tuning is often a standalone business in this industry.

Riders who enjoy track days, dual-sport riding, adventure riding, off-roading and touring all have very different suspension needs. Understanding how to maximize a system’s capabilities in each of these disciplines is a valued task and when factory suspension systems are not adequate, fitting aftermarket components with greater adjustability can be rewarding!

Suspension technicians commonly complete the following tasks:

• Change springs for rider weight or intended riding style.
• Replace fork fluid, fork seals and fork bushings.
• Valve and shim stack changes.
• Suspension set-up adjustments for the rider.
• Replace damaged or worn-out components.

If this sounds like an exciting career to you, completing a motorcycle training program can be a great place to start training for one.^1.1

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Motorcycle Suspension Systems FAQs

1. What are the key factors to consider when tuning a motorbike's suspension?

When tuning a motorbike's suspension, consider the rider's weight, riding style and the type of terrain they'll be encountering. Each of these factors influences how the suspension behaves, affecting comfort and handling. Additionally, take into account the bike's overall geometry and intended use, such as whether it's for city riding or off-road adventures.

2. What steps should I follow to adjust my motorbike's suspension for better handling?

To adjust your motorbike's suspension, start by checking your sag settings, ensuring they are within manufacturer specifications for your weight. Next, fine-tune compression and rebound damping based on whether you're facing bumps, corners or smooth stretches of road. Finally, make small adjustments and test ride to gauge the effect on handling, repeating the process until it feels just right!

3. What makes a motorbike suspension system considered the best on the market?

A top-notch motorbike suspension system combines high adjustability, premium materials and reliable performance across different riding conditions. The best motorbike suspension systems offer precise tuning capabilities to suit various rider preferences and experiences, whether tackling the racetrack or navigating city streets. Additionally, a reputable brand with strong customer support enhances overall value and satisfaction for riders.

4. How does an adjustable motorcycle suspension improve the riding experience?

An adjustable motorcycle suspension allows riders to tailor their bike’s handling characteristics to their specific weight, style of riding and road conditions, providing versatility in performance. This personalization leads to a smoother ride, better traction and improved cornering capabilities, resulting in increased comfort on the bike.

5. What are the benefits of upgrading to a high-quality motorbike suspension system?

Upgrading to a high-quality suspension system can significantly enhance your motorcycle's performance, providing greater control and stability at various speeds and conditions. Premium systems often feature better damping capabilities, reducing bottoming out and improving comfort over rough terrain. Additionally, a well-tuned suspension can prolong the bike's lifespan and contribute to a safer and more enjoyable riding experience.

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Train for a Career in the Motorcycle Industry

In Motorcycle Mechanic Institute’s 48-week Motorcycle Technician Training program,⁷ you’ll be taught the foundations of motorcycles, ATVs, side-by-sides and personal watercraft to prepare for a career as a motorcycle technician—including how to service suspension systems.^1.1

To learn more, visit our program page and request information online or call us at 1-800-834-7308 to get in touch with an Admissions Representative today.

MMI Campuses That Offer Motorcycle Mechanic Training

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