A bicycle suspension makes it easier to ride on hard terrain. Most mountain bikes have a front one, and some also include a rear suspension. There is a lot going on in your bicycle when they compress and expand.
Back in college, I learned a lot about suspensions by designing my own motorcycle. They are a bit different from bicycle suspensions, but most things are the same.
Here you will learn everything you need to know about bicycle suspensions.
Table of Contents
What is a bicycle suspension
It’s the system that keeps the wheels in contact with the ground at all times. The suspension compresses and expands to move the wheels up and down.
As its name indicates, the suspension’s goal is to “suspend” (or hover) the bicycle over bumps and potholes. This decreases your fatigue while increasing control.
Your tires are also a form of suspension. They absorb terrain irregularities and small vibrations for a comfortable ride.
|Just a metal spring. Resists compression and absorbs impacts
|Need complex systems to adjust preload and spring rate separately.
|Linear compression rate
|Progressive compression rate
|High trail sensitivity
|Lower trail sensitivity
|Less adjustment, you may need to replace it.
Usually, these are combined with an oil damper to achieve a smoother ride.
Pros of using suspension in your bicycle
- More comfortable ride.
- Better control of the bicycle.
- Better overall traction.
- Faster on rough roads and downhills.
Cons of using suspension in your bicycle
- Higher price.
- Heavier bicycle.
- Maintenance increases.
- Slower when going uphill.
Bicycle suspension types
Only front-wheel suspension on the fork. This is the most versatile setup. They can carry you through both pavement and trails, which makes it ideal for Cross Country.
Hardtails prevent all the problems that come with a rear suspension. Especially, they are best for uphill riding and smooth trails.
If you want more suspension, you can always raise up from your saddle. That way your knees will act as suspensions and you will become a sprung mass.
A front and a rear suspension make for the best bump absorption. The whole frame becomes a sprung mass, which makes it great for hard trails and downhills. You don’t need to use your knees as suspensions, so these are better if you have joint issues.
As a counterpart, you are adding another piece to your bicycle. The cost and weight increase, as well as the maintenance.
There are many rear suspension configurations depending on the pivot points:
You can easily mistake it for a hardtail. The only difference is a little plastic piece in the swingarm. It is elastic so it will compress and extend to absorb bumps.
There are no pivot points, so the bicycle will behave similarly to a hardtail. It will reduce vibrations and make your ride smoother, but won’t handle rough terrain.
This is the simplest rear suspension design. The swingarm connects directly to the frame at a single pivot point. Then, the shock makes it rotate around that point, so the rear wheel will move in a circle around the pivot point.
Generally, these bicycles have a linear compression rate. They are also easy to maintain because they have few bearings.
A bicycle that connects the swingarm to the main frame at a single point is a single pivot. It doesn’t matter if it has four bars or many linkages.
Unified rear triangle (URT)
On a single pivot, the chainrings are in the frame. But on a URT, they are in the swingarm. This means that your seat is sprung mass, but not your pedals.
The chainrings will always move with the rear wheel, so kickback is completely eliminated. However, the distance between the saddle and the pedals will change as you sit up. You will notice how pedal strokes compress the shock, so pedal bob is high with this one.
It adds a small piece to link the swingarm, the shock and, the frame.
The main advantage of this is that it changes the leverage curve. It allows you to control the compression rate, but it’s a more complicated system.
It’s often called “faux-bar” because it looks similar to a four bar design. It needs a new pivot point above it, but the rear axle is directly connected to the frame, so it’s still a single pivot.
Also called Horst Link. It looks similar to a linkage driven single pivot suspension, but the main difference is in the rear pivot.
The rear wheel is not directly connected to the frame. This allows for different axle paths to reduce and control pedal bob. It also increases the sensitivity of the ride.
Virtual pivot point
Also called twin link, it’s basically a short-link four-bar. But the swingarm is a single piece in a triangular shape. It connects to the frame by two links.
This makes a big difference. Now the rear wheel rotates in an S-shaped path instead of a circular one. The axle path changes from bike to bike, which is useful to modify the anti squat performance.
This design increases the stiffness of the bicycle and reduces the load on the pivots. So it’s pretty common these days.
How bicycle suspensions work
The travel is how much distance a suspension can compress. This affects how much the wheel axle moves.
Due to that, it affects both the bike control and the bump absorption capacity.
- Best for uphill.
- Lower bump absorption.
- High steering sensitivity.
- Best for downhill.
- High bump absorption.
- More stable steering.
It’s the movement of the rear axle due to the suspensions. The swingarm acts as a leverage and so the rear wheel moves differently than the suspension. The difference between the wheel movement and the suspension compression is called the leverage ratio.
Higher leverage needs a stronger suspension to withstand the bump forces. But a low leverage ratio will give you a more accurate sensitivity of the terrain.
You can make most suspensions rigid thanks to a lockout mechanism. This is useful on pavement and to prevent squat when going uphill.
High-tech bicycles have a lever in the handlebar to remotely control the lockout. They can also deactivate it automatically under a certain force thanks to a blow-off system.
Your suspension compresses due to your weight when you sit in the saddle. This movement is the sag, and it’s measured as a percent of the total travel. This is a desired effect because it allows the suspension to extend when dropping into potholes.
The sag helps your wheel stay in contact with the ground at all times, making for a softer ride.
As a rule of thumb, keep your sag between 15% and 25%. Downhill bikes will have a higher one, but you can always change yours with preload.
To preload your suspension is to put in and keep some force before riding. It will keep your suspension compressed and reduce its travel.
This will make your suspension feel harder and reduce sag
Coil suspensions have a knob that you can turn to compress or decompress it. Air springs require adjusting their pressure with a special pump.
The rebound damping controls how fast the suspension extends after it’s compressed. This is what determines the bounciness of your bicycle.
To find the best setup for you, reduce it as much as you can first. Then, keep increasing it until your bicycle bounces only once when you sit on it.
Put too much rebound damping, and you will turn your bicycle into a pogo. Too little, and it will drag you down.
The compression damping controls how fast the suspension compresses.
You want a faster setting if you ride on flat terrain or are lightweight. For heavier riders who bottom out the suspension, it’s best to decrease the compression damping speed.
A slower compression can also help you through rough terrain and landing jumps.
Suspensions do this by making the air or oil go through a valve that difficults the flow.
Whenever you speed up or brake, you experience a force. It’s the same as if someone pushed you. When you accelerate hard, your front wheel tends to rise. And when you brake hard, the rear wheel tends to rise. It’s as if your weight transferred back and forth.
The rhythm of your pedaling creates this oscillation to a lesser extent with every stroke. Especially when going uphill.
Your suspensions will absorb this and compress, preventing the wheels from rising. Yet, this is an undesirable effect because it wastes your energy. Part of your energy is going into compressing the suspensions instead of moving the bike forward. That’s when lockouts come in handy.
It’s produced when you speed up. The rear wheel puts the force forward to move the bicycle. So the front wheel tends to rise and your “weight goes back”.
This sinks your rear suspension and prevents a wheelie.
Anti-rise (Brake Jack)
It’s produced when you brake. The rear wheel tends to rise and your “weight goes forward”. This sinks your front suspension.
But your rear suspension sinks too if you brake with your rear brake. This is because of the wheel inertia.
The rear wheel is rotating at a fast speed. Suddenly, you press the brake and it stops. This deceleration creates a force in the brake itself that the suspension absorbs. This is called anti-rise, because it shrinks your bicycle instead of rising it.
Also called pedal feedback. When the rear suspension compresses, the rear wheel moves in a circle. But its center is on the pivot point, not in the chainrings. This increases the distance between the wheel and the chainring.
But the chain has a fixed length, so the gears must rotate to accommodate this growth. This moves the cranks against your pedaling.
What to look for in a bicycle suspension
Look for suspensions of known brands and manufacturers. Every bike shop and professional will be able to service them, and there are lots of spare parts. You will save in the long run.
Also, they are usually stronger and last longer.
Nice suspensions are expensive. You don’t need the best one out there, so make sure to get the one that fits you better. Check with different shops to find the best deal.
Suspensions are heavy, especially coil ones. Check if it’s best for you to have a light bicycle or a nice suspension. Most of the time, a hardtail will be enough. Especially if you are looking for speed or going uphill.
Make sure that your suspensions have plenty of adjustment options. Preload, compression, and damping are the most important ones.
You may need to replace a coil spring to find a suitable suspension setup. But an air spring will usually have all the adjustment options you will need.
It’s also a plus if they have a lockout option.
Bicycle suspension maintenance
Servicing your suspensions can be expensive. Follow these maintenance guidelines to extend their lifetime.
Keep your stanchions clean
Clean them after every ride. Floss through the whole tube with a soft cloth to remove dust. You may need to lube them near the seal, so make sure to check the manufacturer’s manual.
If your stanchions have any scratches you must change them. It could break the dust seal and ruin your whole suspension.
Check with a professional
Look for a professional in the following cases:
- The suspensions don’t work properly.
- The stanchions and sliders have play.
- You notice some oil in the stanchions.
- The air springs don’t have any travel, or lose their air.
Don’t even think of disassembling a suspension by yourself. Springs have a lot of strength and can be dangerous if you have no experience. They are complicated devices that can hit you in the face while trying to open the suspension up.
Instead, have a professional service them periodically. This will extend their lifetime, especially if you ride regularly. They are expensive to replace.
How to replace a bicycle suspension
You have to make sure that the new suspension system is compatible with your bike frame. First of all, make sure that the total size fits your bicycle. You don’t want to end up with a child-sized suspension.
Check also the suspension travel. If the newer one has too much or too little travel, it could change the geometry of your bicycle. Incorrect suspensions will affect handling and be dangerous.
The axle dropout must be the correct one to ensure axle compatibility. Same with the steerer tube.
If you want to change the fork suspension, you must also check the brakes. Most rim brake mountings are not compatible with disc brakes.
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