How to Adjust Your Mountain Bike Suspension

How to Adjust Your Mountain Bike Suspension

Adjusting your suspensions is important, and it's personal too as it depends on your weight, how you ride, and how you feel on your bike. Properly adjusting your suspensions is an essential part of mountain biking, as an improper adjustment can lead to falls. So, how do you properly adjust your fork? How much pressure should you add to your shock absorber? Read on for our tips on how to adjust your suspensions.

The different types of MTB

When it comes to suspensions, there are three types of mountain bikes:

- Rigid MTBs have no suspension. They are somewhat the ancestor to today's mountain bike though it is making a comeback amongst some riders. Perfect for riding on (very) smooth ground, it is highly responsive, with good pedaling performance, but is uncomfortable compared to the other two types.

- The hardtail MTB has a front suspension, a so-called "suspension fork". There are many varieties: forks with a double-T, inverted forks, "single-arm", etc. Here we only deal with classic air forks or those with a helicoidal spring (coil), but in general the adjustments are pretty much the same.

- The full-suspension MTB has two suspensions: a front suspension with a suspension fork and a rear suspension commonly called a shock absorber or simply shocks.

Note that the above three bikes have two "suspensions" mechanisms in common which are often overlooked: the frame and the tires. The architecture, geometry and composition of the frame will absorb and cushion some shocks by deforming ever so slightly as you ride. Next come the tires, which depending on their dimensions and air pressure, will cushion small shocks and smooth the ride.

Everything you need to know about your suspensions

How does a MTB fork work? Your fork and your shocks (if your bike has them) generally work the same: a spring deforms as it absorbs the energy of a shock. But to learn how to properly adjust your suspensions, you need to first know what they do!

1) The type of spring

In order to function, a fork and/or shocks need a "spring effect" that can absorb energy and then release it to return to its initial position. These suspensions are made with two types of springs: a helicoidal spring (or simply coil) and a pneumatic spring (with air).

2) Travel

The "travel" of a fork is the maximum distance the fork can travel before it hits the stopper; it is expressed in mm. This distance ranges from 80mm for bikes designed for flatter terrain to over 200mm for descent MTBs.

3) The sag

The sag refers to the travel of the coil or pneumatic spring when cushioning a shock. When bumping against irregular features of the terrain you're riding on, the inner legs (stanchions) of your fork descend into the outer legs (sliders) to dampen the shocks. The shock absorber works the same way

4) The hydraulic system

Most shock absorbers and medium- to high-end range forks have a hydraulic system. This is a cartouche that is made of a perforated piston moving through oil which slows the movement of the stanchions into the sliders in order to keep the bike steady. This reduces the rebound of the suspensions after the spring release effect

How to adjust your sag

1) Determining the sag of your fork and/or shock

The first adjustment to make on your suspensions is the sag. The goal is to define the best level of hardness of the spring based on your weight as the rider, your riding style, the type of terrain, and your personal preference.

With that in mind, let's calculate the sag. As a reminder, the sag is the amount of suspension travel when you are sitting on your bike. It is calculated as a percentage of total travel. For example, if you want a sag of 20% on a fork with 100 mm of travel, the fork should descend by 20 mm (100 * 0.20 = 20) when you're in a riding position on your bike.

Some typical sag ranges are:
- For trekking, you're looking for comfort and therefore want a relatively high sag (around 20-25%).
- For cross-country that is more performance oriented, you'll want a firmer suspension (15-20%).
- For all-mountain or gravity riding (enduro/downhill), you'll want a much higher sag to smooth out the terrain and cushion the big shocks (25-30%).

These numbers are simply reference points to get you started. You can then adjust your sag as you get more used to riding based on your personal preference as you ride your bike.

If your bike has a Rockshox fork, you can use their Trailhead app and enter the serial number of your fork, which you'll find indicated on the back of your fork's T. Then click Customize and fill in the fields to get the recommended pressure and number of rebound clicks.

P.S.: For all-suspension mountain bikes, we'll want slightly more cushioning in the rear suspension, up to an additional 5% of sag. However, take care that your front and rear sag aren't too far apart as your bike won't be balanced and that will reduce its manoeuvrability.

2) Adjusting your sag

Let's start with the simplest: suspensions with a helicoidal spring (coil)
With this type of suspension the adjustment dial that regulates the coil tension is typically located on the T of your fork, on the right side. It is often labelled preload. Simply turn the dial clockwise to tighten the spring, and counter clockwise to loosen it.

Adjusting a U-Fit fork is even easier! The dial shows a number that corresponds to the weight of the rider, fully loaded (helmet, bag, shoes, etc.). Simply turn the dial until it shows your weight, and you're done!

For an air suspension (pneumatic spring), you'll need to get a high-pressure pump for suspension in order to inflate your air chamber. The higher the pressure inside the chamber, the firmer the spring will be. In other words, the more sag is desired the less air should be injected, and vice-versa. The valve through which to pump in air is typically located on the left side of the T of the fork.

Note: Don't over-tighten the cap on the air valve; its purpose is not to keep air in but rather to protect the valve from external elements such as mud or dust.

Now that we know how to adjust the hardness of the spring, next we need to learn how to obtain the correct sag!

To check if you have the correct sag, put a rilsan (nylon) clamp around one of the dampers. If your fork or shock has an O-ring (also called toric joint) on the damper, you don't need to put a clamp. Get all your cycling gear on: helmet, shoes, bag, glasses, protections, then get on your bike.

Sit on the bike, pedals horizontal, hands on the handlebar, and lean against the wall with your elbow or have someone hold you up.
Slide the O-ring or the nylon clamp down to the fork seal, then get off the bike while taking care not to compress the suspension.
Determine the amount of travel obtained by measuring the distance between the O-ring and the fork seal. Then calculate the proportion of this travel relative to the maximum travel of your suspension, and you will have your sag.

Here's a little formula to help:
(total travel * 100) / fork travel = sag

If your sag is too high, loosen the coil spring or let some air out of your pneumatic spring. If it's too low, then do the reverse: tighten the coil spring, or add more air. Then repeat the test! Important: if you change the pressure of your suspension, remember to pump your fork or shock absorber two or three times in order to distribute the air between the positive and negative chambers (if you have an air suspension fork).

How to adjust your rebound

Now that you've adjusted your sag, it's time to adjust your rebound.

Check whether your fork is equipped with a dial to adjust the rebound. On the vast majority of forks, this dial is found under the right stanchion. It is often marked with SLOW (or +) which indicates the slowing of the rebound, and FAST (or -) for a faster rebound. On Rockshox forks, tortoise and hare icons are used to indicate the direction in which to turn the dial. (Hare for faster, tortoise for slower.)

But we're getting a little ahead of ourselves, because first we need to understand what the fork rebound is!
How to adjust your suspensions properly.
Remember: adjusting the rebound (or release) determines the speed at which the suspension returns to its initial position after having cushioned a shock.
If it is too fast, you may feel a recoil effect that could destabilize the bike or even throw you off. If you're new to mountain biking, we recommend that you not set the rebound at the highest level unless you're used to ejection seats (stuntman, aeroplane pilot, etc.)

Conversely, if the rebound is too slow when riding on very uneven ground your suspension won't have time to fully return to its starting position before having to cushion the next shock and you'll quickly find it bumping against the stopper.

So your adjustment will depend on three criteria: your weight, your riding style, and the terrain you ride on.
For example, a beginner rider on smoother terrain will want a slower rebound than a more experienced rider riding over more uneven or bumpy patches. Very uneven terrain with long screes, steps, or jumps requires a fast rebound.

The best way to find the correct rebound setting for you is to trust how you feel when riding. Set out with the correct sag and with the rebound set to medium, and adjust the rebound periodically as you ride. You'll learn to recognize when the rebound is too fast or too slow. What you don't want is for your bike to be difficult to handle because the rebound is too high, nor risking your suspension bottoming out because the rebound is too slow.
The right amount of rebound is one that smooths out the terrain as much as possible.

Note: The Rockshox Trailhead app will show the recommended rebound for Rockshox forks.

How to adjust the compression of your suspension

After adjusting the sag and the rebound (release), you can now adjust the compression of your fork. This adjustment is a bit more complicated than the two previous ones. Remember: adjusting the compression will change the speed at which the suspension descends (compresses). It is adjusted using a dial (typically blue in colour with the marking CHARGER or COMPRESSION) on the right side of the T of the fork.

Entry-level suspensions typically don't come with a way to adjust the compression; others only have two positions (open, closed), others have a single compression adjustment that can be set to several positions, and lastly, high-end MTB enduro/gravity forks have two compression adjustment mechanisms.

1. Locking the suspension
On some forks and shocks, the compression dial has only two positions: open and closed. When the dial is in the open position, the suspension works normally. When in the closed position, the suspension is much more rigid, nearly "fully-locked", which yields better performance on smoother terrain, uphill climbs, or riding on paved roads.
To lock the suspension simply turn the dial which is located either on the handlebar or on the suspension itself, depending on the model.

2. Low-speed compression adjustment
This adjustment is only on suspensions that have one or two compression adjustments made using a dial with several positions. When the fork or shocks only have a single compression adjustment, this adjustment regulates the low-speed compression.

What is low-speed compression?
It concerns compressing the suspension at the start of a ride or when riding over small bumps, when braking, or when pedalling force is applied by the rider.

A low speed compression setting that is too open can result in a loss of traction when applying force, braking, or on a raised turn or banked curve. Conversely, a low speed compression setting that is too closed will make your suspensions too firm and you will feel the jitter from small bumps much more in your arms.

3. High-speed compression adjustment

This adjustment is only found on suspensions that have two compression adjustment mechanisms. The central ring is for the low-speed compression, while the outer ring is for the high-speed compression.

What is high-speed compression?
It's the compression of the suspension at the end of the course, or over large bumps such as very uneven terrain, or when landing jumps.

If during steep descents over very uneven ground you feel you don't have enough manoeuvrability or that your bike is shaking too much, your high-speed compression setting is too closed. Conversely, if you feel that the fork or shock goes in too far on impact it's because your high-speed compression is too open.

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