How to setup front suspension

Front Suspension setup is dynamic and specific to the bike and rider. Significantly, a lot of factors affect it’s performance and is key to making your trail-riding fun and exciting. Here we talk about the different types of forks available and a guide on how to setup and tune your front suspension to get the most out of it.

What Is A Coil Fork?

Coil forks use a metal coil spring to provide resistance. Moreover, coil forks have a linear spring rate. This means that the force required to compress the spring increases constantly throughout the fork’s range of travel. Furthermore, cheaper coil spring forks found on leisure ebikes and cheaper eMTBs have limited adjustment available. Therefore, you may be only able to adjust preload and rebound.

To adjust the spring rate of a coil fork, you can swap out the coils for stiffer or softer options. You can set the fork sag by turning a dial on top of the stanchions. Explicitly, this changes the preload on the springs by compressing or decompressing the springs. Increasing the preload compresses the spring, which makes the fork stiffer and reduces sag. Incidentally, most coil forks also have a lockout function to prevent them from compressing.

Suntour coil spring forks

What Is An Air Fork?

Air forks use the compressed air resistance for shock absorption. The spring  is provided by compressed air that is sealed in an airtight chamber inside of the fork leg and is called the air spring. As the fork travels, air is compressed and resists further compression. Air forks are used for all types of mountain biking including, but not exclusively, trail riding, downhill, cross country, enduro, and freeride.

The spring rate of an air fork can be adjusted by changing the air pressure inside the fork leg. Accordingly, increasing the pressure increases the spring rate and makes the fork stiffer. Decreasing the pressure makes the fork softer. Adjusting the pressure of an air fork requires a special high-pressure pump called a shock pump. You simply attach the pump to a Schrader valve on the fork and add or remove air. You also adjust the fork preload and sag by changing the pressure. There are no preload dials like you would find on a coil fork. Most air forks can also be locked out so they do not compress

On more expensive air forks you can also adjust the progression by changing the volume of the air chamber. This is achieved by adding or removing plastic spacers inside. Comparatively, adding spacers decreases the volume inside of the air chamber. Reducing the volume makes the fork more progressive or harder to compress earlier in the range.

Air forks also have a damping system to smooth out your ride over bumps and compressions. Most models allow you to adjust the compression and rebound damping.

Fox Air Fork

Why Bother Setting Front Suspension Up?

Good front suspension setup can make a good bike feel great, but a poor setup can make a great bike feel terrible. Here are some steps to help you optimize your bike for your weight, your trails  and your style. Investing time setting up your suspension will transform your ride and you!

Be Prepared To Compromise

Firstly, a perfect front suspension setup does not exist. Suspension setup is always a compromise, generally finding a balance between sensitivity on trails and support for bigger impacts. Furthermore, your suspension is unique to you, your trails and your style of riding them. While most fork manufacturers now offer printed guidelines that will give you a setup normally based on weight of the rider, following this guide will help you to personalise it.

Be Ready

Before you start to play with your forks, you need to ensure that they are in good working order.  Check your front suspension manufacturers recommended service intervals and make sure you have the work done. Suspension forks are expensive so look after them. If you’re setting up a new bike you don’t have to worry, but if your bike has seen action it is essential to get your forks serviced by professionals – it will transform the performance of your bike and you!

To follow this guide you will need your normal riding clothes, helmet and backpack on. To best optimize your bike’s performance you will need a short section of your favourite technical trail, a shock pump, a measuring device (ruler or tape), a calculator and someone to help you.

#1: Setting Your Fork Sag

For your front suspension setup to perform well, it must be able to respond to every bump on the trail. When you hit something, your fork will compress, absorbing the energy from the impact and then, consequently, this is released by extending back out again. Getting this balance right is important to maintain traction. In order to let the suspension both compress and extend, we preload the suspension with our own body weight.  Sit on the bike and the fork will compress slightly. This is known as sag .

If you have a rear shock. Set up your rear shock first.

Make sure your front suspension damping is fully open and adjust the air-spring pressure to the manufacturer’s recommended psi. Have your assistant support the bike as you climb on.

  1. Bounce the front wheel firmly up and down to get your fork ready
  2. Assume a standing, riding position then allow the bike to settle for a few seconds. Ask your assistant to slide the rubber O-ring on the fork stanchion down to the rubber wiper seal.
  3. Carefully dismount without disturbing the O-ring.
  4. Measure the distance the O-ring has been pushed up from the wiper seal in mm. Divide this number by the total fork travel available (eg 140 mm) and then x 100 to get the percentage sag.
  5. To achieve the correct sag, add or remove air from the air-spring as needed and repeat.

Start with the manufacturer’s recommendation or we would suggest 20-25%. If you require less sag simply add air to the fork to make it firmer, if you require more sag let some air out. Add air in 10 psi increments and each time repeat the process until you reach the required sag.

#2: Optimising Your Spring Rate

While 20% sag in the fork is a good base setting, it may not be optimal for your riding style. Remember, your spring rate is always a compromise between the big hits and small bumps. The optimum settings for you will depend on your riding style and the trails you ride.

Now you need to find a trail you use regularly that offers as many features as possible. Jumps, bumps, berms, compressions, rocks, drops. Whatever you ride the most. After a few runs to warm up, push the O-ring down to the wiper seal and ride the trail. Concentrate on how big impacts and drops feel. Is your fork bottoming out? Does it feel harsh on singletrack? Are you getting full travel?

If your suspension fork compresses sharply when you brake or ride very steep downhill trails
Your air spring rate is too low. Add pressure 5-10 psi at a time and repeat the trail. Stop when the fork firms up enough and gives you good support. Make a note of the pressure.

If your fork feels harsh over small bumps and lacks grip
Your air spring rate is too high. Remove pressure 5-10 psi at a time and repeat the trail again. Stop when the fork feeds back over small bumps but still has good support. Make a note of the pressure.

Pro-Tip: If you find that the only way to stop frequently bottoming out your suspension fork is to use a high spring pressure that feels very harsh over small impacts, you may need to increase your spring rate progression, see Step 3.

TEBS Banner

#3: Consider Your Spring Rate Progression

We now have to consider you as a rider and what trails you are riding. If your fork is running low on travel under hard braking and fast corners even though the bike feels good on general trails, you may need to reduce the air volume in your fork. For a more progressive spring rate you need to add volume spacers to reduce the air volume.  Adding these will make the final part of the suspension compression firmer, requiring more force to bottom out.

If you feel that you are bottoming out your fork too frequently, despite running the correct air-spring pressure
Reduce the volume of air in the fork with the addition of 1-2 volume spacers.

If you feel that you struggle to achieve full travel where you expect to
Increase the volume of air in the fork by removing 1-2 volume spacers.

Pro-Tip: If you make big changes to the setup of your fork, such as a firmer spring rate or the addition of volume spacers, tune your rear shock to match. With more confidence from your new fork setup you will inevitably ride harder and your shock will need to be adjusted to your style of riding again

#4: Rebound Damping

Rebound damping controls the speed at which compressed suspension returns after a bump.

If rebound damping is too low (-) your fork will extend too fast and feel spring-like and out of control. If the rebound damping is too high (+) the suspension will not return fast enough after repeated bumps sinking lower into its travel and performing poorly.

  1. To set a base fork rebound, start with your rebound fully closed (+). Stand next to your bike and compress the fork with your body weight. Quickly release the fork and let it return.
  2. Adjust it until the fork rebounds as fast as possible without the front wheel jumping off the ground.
  3. Once the base setting is dialled in, repeat a section of your trail at this setting. Repeat a few times dialling in more and less rebound either side of your base setting to see which feels the best.

But what about high-speed damping? Most suspension forks have a single rebound adjuster, which really is a low-speed rebound adjuster. Some very high-end suspension forks also have high-speed rebound adjustment too. There is a lot of crossover between high and low-speed rebound, any adjustment of one will influence the other. If you do have high-speed rebound adjustment on your fork, we recommend setting it to the manufacturer’s recommendation and then adjust as above. High speed damping effectively keeps fork travel in reserve for bigger hits on the trail. The more you add the harsher the bike will feel and is generally set and forget unlike low-speed damping adjustment which is much more tuneable between trails and where most of your tuning and tweaking should be focussed.

Pro-Tip: If you ride slowly or on easy trails, a slower rebound may feel more comfortable. However, if you move to harsher, faster trails you may experience sore arms and legs as your suspension cannot recover fast enough from the bigger hits. Run as fast a rebound setting as you can for best performance.

#5: Get The Balance Right

In nearly all cases a balanced front suspension setup is essential for optimal performance.

As a final check, find some level ground and ride slowly across it on your bike. From a standing, attack position jump repeatedly up and down as hard as you can. The bike should feel supportive and the rebound speed should feel good. If the bike feels unbalanced, identify where it is coming from and make some adjustments.

Traction not only comes from the tyres and terrain surface, but the amount of force the rider is placing on the tyres too. A balanced fork setup is important for this element of traction. 

If you follow this guide, you will have gained a deeper understanding of how each element of your front suspension works. Good suspension performance is a balance between many different factors which we have talked about. If you make any big changes to one setting of your suspension, you need to balance the other settings to match.


Further Reading


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