Understanding Bike Suspension: How It Works and Why It Matters

Why do bikes have suspension? In short, to keep you comfortable and in control when the ground gets rough. Suspension absorbs bumps so they aren’t transmitted directly to you, and it keeps your tires in contact with the ground rather than pinging off every rock or pothole. By smoothing out impacts, a good suspension improves traction (your wheels don’t skip or skitter), which means better braking and more efficient pedaling on rough terrain.

Here’s a rundown of suspension’s main benefits:

• Comfort: Suspension insulates you from bumps and vibrations, reducing fatigue on long or rough rides.
• Control: It helps the wheels track the ground instead of bouncing off, so the bike handles predictably over obstacles.
• Traction: By keeping wheels planted, suspension lets you pedal and brake more effectively without losing contact with the ground.

Not every bicycle needs suspension. It comes with some trade-offs like added weight and complexity. But for many types of riding, the benefits of a well-tuned suspension far outweigh the drawbacks.

How Bike Suspension Works

A suspension system is simply a combination of a spring and a damper. The spring (whether it’s a steel coil or compressed air in a chamber) absorbs the impact by compressing when you hit a bump. The damper (usually using oil and valves) controls the speed of that compression and rebound, preventing the bike from just bouncing. This duo allows the wheels to move up and down with the terrain while the rest of the bike (and you, the rider) stay comparatively steady.

Springs

Most bike suspensions use either a coil spring (a metal coil that compresses) or an air spring (air pressure in a sealed chamber). Coil springs are known for a super plush, linear feel and consistency, while air springs are lighter and easily adjustable. Air shocks and forks have become very popular because you can tune them to your weight and riding style with a simple shock pump, whereas coils might require swapping to a different spring to change the stiffness.

Damping

Springs alone would just bounce uncontrollably, so suspension includes damping to control motion. Oil-filled dampers inside the fork or shock force oil through tiny valves as the suspension moves, which slows down the compression and rebound. By adjusting the damper settings, you can change how fast the suspension compresses over a bump (compression damping) and how fast it springs back (rebound damping). Most modern suspensions have clicker knobs or dials so you can tweak rebound and sometimes compression to your personal preference.

Sag, Travel, and Lockout

There are a few other terms you’ll hear when talking about suspension.

• Travel: Travel refers to how much movement a suspension has – for example, a fork with 120 mm of travel can compress up to 120 mm under load.
• Sag: Sag is how much the suspension compresses just from the rider’s weight when you’re stationary. Typically, you set your suspension to sag about 20–30% into its travel when you sit on the bike; this ensures the wheel can move both up and down to follow the terrain.
• Lockout: Lockout is a feature on many forks and shocks that essentially “locks” or greatly stiffens the suspension for times you don’t want any movement (like grinding up a smooth hill or sprinting on tarmac). Think of it as a temporary off switch for your shocks to make the bike behave like a fully rigid bike until you unlock it.

Suspension Across Different Bike Types

Not all bikes use suspension, and those that do may have it in different forms. Let’s run through the main categories of bikes and see what kind of suspension (if any) each uses.

Mountain Bikes (Hardtails vs. Full Suspension)

If you picture a bike with suspension, you’re probably imagining a mountain bike. Mountain bike suspension has advanced the most – it’s essential when rolling over rocks, roots, and drops on the trail. There are two main kinds of MTB setups:

Hardtail: A mountain bike with front suspension only (the rear end of the bike is a rigid frame).

Hardtails have a suspension fork to soak up impacts on the front wheel, but no rear shock. The rear wheel has no suspension other than the flex of the tire and frame. They’re popular for cross-country riding and racing, where efficiency and low weight sometimes matter more than maximum bump absorption. A hardtail still gives you cushion up front for trail chatter, but the rigid rear means you as the rider have to absorb more bumps with your legs. The upside is a more direct power transfer (no energy lost compressing a rear shock when you pedal), which can make hardtails feel snappier on climbs or smoother trails.

Full Suspension: A mountain bike with both front and rear suspension.

Full suspension bikes have a suspension fork up front and a rear shock connected to some kind of pivoting frame linkage that allows the rear wheel to move. Full-suspension bikes dramatically increase comfort and control on rough terrain, since both wheels can absorb bumps. The trade-off is extra weight, cost, and complexity (there are pivots and bearings that require regular maintenance). A good design will minimize “pedal bob” (the suspension moving as you pedal) and brake dive, while still swallowing big hits.

Gravel and Road Bikes (Compliance vs. Suspension)

Gravel bikes and road bikes typically don’t have the obvious suspension bits you see on MTBs – no big fork or rear shock – but that doesn’t mean they’re completely rigid in practice. These bikes rely mostly on frame design and tire choice for shock absorption, a concept often called compliance rather than suspension. For example, a gravel bike with high-volume 40 mm tires at low pressure will soak up a lot of chatter from washboard gravel. Many endurance road and gravel frames are engineered to flex just enough in certain directions to dull the sting of rough roads. Even seatpost material makes a difference; a thinner or carbon seatpost can flex and act like a tiny suspension element under the saddle.

Thomson’s titanium seatpost is a great example. Its natural flex adds a bit of shock absorption and takes the edge off bumps on gravel or road rides. 

That said, modern gravel bikes are increasingly adopting active suspension features as riders push these bikes faster on rough terrain. A few innovations you might see:

• Short-Travel Suspension Forks: Some gravel bikes now come with mini suspension forks. These forks are much lighter than MTB forks and designed to smooth gravel vibrations and small bumps without being overkill.
• Suspension in the Frame or Headset: Manufacturers have gotten creative by building suspension into non-moving parts. These systems are usually quite subtle – you might not even notice a pivot or spring at first glance – but they aim to give you a smoother ride without turning the bike into a full-suspension machine.
• Suspension Seatposts and Stems: A popular retrofit for gravel riders is a suspension seatpost (like the Cane Creek eeSilk or Redshift ShockStop seatpost) or a suspension stem. These components use either elastomers, springs, or small linkages to allow a centimeter or two of cushioned movement. For example, a suspension stem will pivot slightly to absorb bumps at the handlebars, and a suspension seatpost might have an internal spring or flex mechanism to soften the blows to your backside.

So, do gravel/road bikes need suspension? They primarily rely on passive suspension (tires, frame flex, etc.) to keep things comfortable, but there’s a growing category of active suspension tech tailored to drop-bar bikes. If you mostly stick to smooth pavement, you likely don’t need fancy suspension. But if your road or gravel rides venture into rough terrain, don’t be afraid of a little suspension help.

Urban and Hybrid Bikes (Comfort on a Budget)

City bikes, hybrids, and many e-bikes built for urban use often feature simpler forms of suspension. The goal here isn’t ripping down mountain trails, but rather adding comfort for everyday riding – think potholes, curbs, cobblestones, etc. The most common setup on hybrids and city bikes is a basic front suspension fork, usually with around 50–80 mm of travel. These forks are typically coil-sprung (with maybe a preload adjust knob at best) and not nearly as advanced as mountain bike forks, but they do absorb the sting of big bumps on your commute.

You might also see suspension seatposts on some comfort-oriented bikes. These often use an internal spring or elastomer and allow the saddle to move a bit vertically when you hit a bump. Even some cruiser-style saddles have springs under them, all serving the same purpose of suspension: making the ride smoother.

Track and Road Racing Bikes

Track bikes and road racing bikes stay rigid for maximum efficiency. On a velodrome or a perfectly smooth road, any suspension would just introduce unwanted movement. Track bikes have a single fixed gear and no brakes. They are the ultimate no-frills machine, and suspension has no place when every bit of power needs to drive you forward. Similarly, an ultra-light road racing bike is designed to be as stiff as possible for sprinting and climbing; those riders will tolerate a bit of road buzz if it means no energy is lost to suspension bob.

Weighing the Trade-Offs: Is Suspension Right for You?

As we’ve seen, suspension is a fantastic innovation that has opened up new possibilities for where and how we ride. It smooths the ride, keeps you in control, and can even make you faster on rough terrain by maintaining traction. But it’s not without downsides. It’s worth summarizing the pros and cons:

Advantages of Suspension

• Smoother ride: Less fatigue and more comfort over long distances.
• Better control and handling: Wheels maintain contact and don’t deflect off every bump, improving stability on rough surfaces.
• Improved safety: Suspension can absorb unexpected hits, helping prevent loss of control or crashes.
• Protects the bike: Cushions big hits to reduce impact stress on the frame and components.
• Adjustable systems: Many suspension setups can be fine-tuned to match your riding style.

Disadvantages of Suspension

• Added weight: All those forks, shocks, and linkages come at the cost of extra grams (or pounds). For example, a carbon hardtail might be several pounds lighter than a similar full-sus bike, which is significant if you’re carrying the bike upstairs or sprinting up hills.
• More maintenance: Suspension components need periodic care. Neglecting suspension maintenance can lead to poor performance or damage, so there’s an ongoing responsibility once you own one.
• Slight energy loss: When you pedal hard, some of your energy can go into compressing the suspension instead of driving you forward (often called pedal bob).
• Complexity: This is both mechanical and in terms of tuning. Mechanically, more moving parts means more potential points of failure. In terms of user complexity, a new rider might be a bit overwhelmed by setting sag, adjusting rebound, etc.
• Aesthetics/Feel: This is subjective, but a sleek road bike or classic steel frame has a certain elegant simplicity that a chunky suspension bike lacks.

Ultimately, the decision of how much suspension (if any) you want comes down to where you ride and what you value. One thing is for sure: the bike industry has blurred the lines by introducing clever micro-suspension tech, so you can get a taste of suspension benefits without going all-in on big shocks.

As a company that’s been making bike components for decades, Thomson has witnessed suspension evolve. We’ve even integrated some of those ideas into our products by choosing materials and designs that complement a bike’s suspension. Our carbon and titanium components are chosen not just for weight, but also for how they can subtly damp vibrations. It all adds up in the pursuit of a smoother ride.

Smooth Rides Ahead

Bike suspension can sound complicated, but it boils down to a simple goal: making your ride smoother, faster, and more fun when the terrain gets rough. By absorbing bumps and keeping your wheels planted, suspension gives you the confidence to tackle trails and the comfort to enjoy long rides on imperfect roads. 

At Thomson, we’re all about elevating your ride experience. That’s why we’ve focused on strong, precision-made components that work with your bike’s suspension. We know that a great suspension fork or shock performs best when it’s paired with a solid cockpit and reliable seatpost, so we build those parts to aerospace standards of quality. Our aim isn’t to sell you on any particular bike style, but to help you understand your bike better.